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PII: S1470-2045(01)00486-7






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PII: S1470-2045(01)00486-7 PII: S1470-2045(01)00486-7 Document Transcript

  • Reviews Global cancer statistics in the year 2000 D Maxwell Parkin Estimation of the burden of cancer in terms of incidence, mortality, and prevalence is a first step to (a) (b) appreciating appropriate control measures in a global context. The latest results of such an exercise, based on the most recent available international data, show that there were 10 million new cases, 6 million deaths, and 22 million people living with cancer in 2000. The most common cancers in terms of new cases were lung (1.2 million), breast (1.05 million), colorectal (945 000), stomach (876 000), and liver (564 000). The profile varies greatly in different populations, and the (c) evidence suggests that this variation is mainly a consequence of different lifestyle and environmental factors, which should be amenable to preventive interventions. World population growth and ageing imply a progressive increase in the cancer burden – 15 million new cases and 10 million new deaths are expected in 2020, even if current rates remain unchanged. Lancet Oncol 2001; 2: 533–43 Globalisation implies more than the application of market Lung Breast Colon/rectum Stomach capitalism free from constraint by local or national authority. Liver Cervix Prostate Oesophagus Health and disease are increasingly seen in a global context, and a proliferation of reports from international1–4 and non- Figure 1. Worldwide data (2000) for cancer in both sexes. (a) Incidence, governmental organisations,5 and from individuals6 provide (b) mortality, and (c) prevalence. statistical data on health-related indices. Of course, these reports have a purpose beyond simply describing the status dying from a specific cancer, whereas survival (1-fatality) quo. The distribution of disease between different represents the probability that an individual with cancer populations and over time helps to define causal hypotheses, will not die from it. Mortality rates are frequently used as a and to quantify the potential for prevention. Data on disease substitute measure of the risk of acquiring the disease occurrence and outcome are essential to forming health (incidence) when comparing different groups, since these policy, by quantifying health problems, helping to define data may be more generally available. However, this priorities for preventive and curative programmes, and for approach assumes equal survival/fatality in the populations evaluation of their outcomes in relation to resource inputs. being compared. Since this is rarely correct – there are, for With respect to cancer, various statistical indices may be example, quite large differences between countries – used, but the most basic indicators of cancer burden are mortality is a more appropriate measure of outcome than listed below and data for these indices in 2000 are shown in occurrence. Figure 1. G Prevalence: the number of people alive with the disease of GIncidence: the number of new cases occurring, expressed as interest at a particular time. There is no clear agreement on an absolute number of cases per year or as a rate per 100 000 what is meant by ‘having’ cancer. Some authors take it to people per year. The latter estimates the average risk of mean ever having been diagnosed with cancer, even if this developing cancer, and is used for comparisons between was many years ago, and the patient is cured. This populations (countries, ethnic groups, or different time definition makes little sense. It would be more useful to periods). Primary prevention strategies aim to reduce incidence. DMP is at the International Agency for Research on Cancer, 150 cours Albert Thomas, 69372 Lyon, France. Tel: +33 (0)4 72 73 84 G Mortality: death provides an unambiguous measure of the 82. Fax: +33 (0)4 72 73 86 50. Email: parkin@iarc.fr outcome or impact of cancer. It is the product of the Correspondence: Dr D Maxwell Parkin, MD, Unit of Descriptive incidence and the fatality of a given cancer. Mortality rates Epidemiology, International Agency for Research on Cancer, therefore measure the average risk to the population of 150 cours Albert Thomas, 69372 Lyon, France. THE LANCET Oncology Vol 2 September 2001 533 For personal use. Only reproduce with permission from The Lancet Publishing Group.
  • Review Global cancer statistics consider people as ‘alive, with cancer’ if they are still from incidence, using survival data specific to a country or receiving some form of treatment or, at least, being region. followed up medically for the disease. Such a statistic is not The country-specific incidence and mortality rates were only hard to obtain, but would certainly vary between estimated for 24 different types of cancer by sex, for five populations, depending on medical practice. However, broad age groups (0–14, 15–44, 45–54, 55–64, and 65 years since ‘cure’ is often taken to equate with survival beyond 5 and over). Age-standardised rates (ASRs) were calculated by years, at least for statistical purposes, a compromise is to use of the weights of the ‘world standard’ population (0.31, estimate prevalence as the number of people alive who have 0.43, 0.11, 0.08, and 0.07) in the five age groups. had cancer diagnosed within the last 5 years.7 Prevalence was estimated from incidence and survival.7 Other more complex statistics have been used to measure Population-based survival data were collected from three the impact of disease. For instance, person-years of life lost, sources: the USA,10 several European countries,11 and less defined as how many years of normal lifespan are lost due to developed countries.12 deaths from cancer. Disability-adjusted; or quality-adjusted A full description of the data used for each country, and life-years lost attempt to give a numerical score to the years the detailed set of estimates, are available on a CD-ROM, lived with a reduced quality of life between diagnosis and GLOBOCAN 2000. This CD-ROM contains computer death (where quality = 0) or cure (quality = 1). programs to analyse and present the cancer database.13 The In this article, the relative importance of different cancers database itself can be downloaded from the Internet worldwide is presented as the absolute numbers of people (http://www.dep.iarc.fr/globocan/globocan.htm), and this developing, living with (5-year prevalence), or dying from, website also includes the most recently available incidence cancer in the year 2000. and mortality rates from different countries. The most recent incidence and mortality data available are from 3–10 years Estimation ago. These rates are used together with population estimates The global estimates are built up from estimates of incidence, in 200014 as the best possible estimate of global cancer burden mortality, and prevalence in every nation in the world. The in 2000. Incidence and mortality rates were not projected to methods used have been described with respect to earlier 2000, partly because historic patterns are not always a sound estimates for 1990.7–9 The basic data are the best available basis for future projections of time-trend data. In addition, information on incidence, mortality, and survival in a for most of the world, there are simply insufficient historical country. Incidence rates are obtained from cancer registries. data to permit such modelling. It is not easy to predict what They may cover entire national populations or selected effect the use of ‘old’ rates (mainly from 1993–97) will have regions. They also provide statistics on cancer survival, on the accuracy of the ‘burden’ estimate for 2000. For cancer enabling incidence to be estimated from mortality. Mortality sites for which rates are generally increasing worldwide (for data, derived from the registration of deaths, are available for example, incidence of prostate and breast cancers), there will many countries, via the World Health Organization be an underestimate of new cases, and where there is a global (http://www.dep.iarc.fr/dataava/globocan/who.htm). decrease, such as stomach cancer, there will be an However, the detail and quality of the data (both the overestimate. However, for several sites, trends are in accuracy of the recorded cause of death and the completeness different directions in different world regions, and are likely of registration) vary substantially. Two types of correction to have changed direction in the past decade, such as lung, were applied to adjust for quantified under-recording of colorectal, and cervical cancers, so the net effect is difficult to deaths, and to redistribute deaths recorded as ‘uterus cancer’ guess. to the specific sites of cervix or corpus uteri. Estimation The estimates vary in accuracy, depending on the extent methods were used when one or more indices were and validity of the data available for each country. Thus, for unavailable. For example, national incidence rates were the Nordic countries there are high-quality incidence and estimated, in order of priority, from: mortality statistics available nationally, whereas for several GNational incidence data from good-quality cancer registries less developed countries there are no available data at all, and GNational mortality data, with estimation of incidence using the estimate is made from data obtained from neighbouring sets of regression models, specific for site, sex, and age, populations (for instance, Afghanistan, Mozambique, and derived from local cancer-registry data (incidence plus Ghana). Nevertheless, the method does rely on use of the best mortality). available data on cancer incidence and/or mortality at GLocal (regional) incidence data from one or more regional country level, and permits continuous updating of the cancer registries within a country. GLOBOCAN database, as newer data become available. This GFrequency data, when only data on the relative frequency of ‘data-based’ approach is rather different from the modelling different cancers (by age and sex) are available. The method used in other estimates.15–18 Essentially, these use sets frequencies are applied to an estimated ‘all sites’ incidence of regression models, which predict cause-specific mortality rate, derived from existing cancer registry results. rates of different populations from the corresponding all- GIf there are no data, the country-specific rates are those of cause mortality.19 The constants of the regression equations the corresponding region (calculated from the other derive from datasets with different overall mortality rates countries for which estimates could be made). (often including historic data from more developed Analogous procedures were followed for mortality, countries). Cancer deaths in these regression models are then so that, for countries where mortality data were unavailable subdivided into the different cancer types, according to the or known to be of poor quality, they were estimated best available information on relative frequencies. 534 THE LANCET Oncology Vol 2 September 2001 For personal use. Only reproduce with permission from The Lancet Publishing Group.
  • Global cancer statistics Review The 2000 estimates We estimate that there were 10.1 Men Women million new cases, 6.2 million deaths, 5.3 million cases 4.7 million cases and 22 million people living with 4.7 million deaths 2.7 million deaths cancer (within 5 years of diagnosis) in 2000 (Figure 1). These estimates are Lung 902 337 810 293 based on the most recent incidence and Breast 1050 mortality data available. The total ‘all 370 Colon/Rectum 499 446 cancer’ excludes non-melanoma skin 255 234 cancers, because of the difficulties of Stomach 558 318 measurement, and consequent lack of 405 241 Liver 398 166 data. The 2000 estimate represents an 384 165 increase of about 22% in incidence and Prostate 543 mortality since our last comprehensive 204 Cervix uteri 471 estimates in 1990.8,9 The cancer profile 233 varies, depending on whether Oesophagus 279 133 incidence or mortality is the focus of 227 111 Bladder 260 76 interest, as shown in Figure 2. In terms 99 33 of incidence, the most common Non-Hodgkin 167 121 cancers are those of the lung (12.3%), lymphoma 93 68 Leukaemia 144 113 breast (10.4%) and colon and rectum 109 86 (9.4%). The most common causes of Oral cavity 170 97 81 47 death due to cancer are cancers of the Incidence Pancreas 116 101 lung (17.8%), stomach (10.4%) and 112 101 Mortality liver (8.8%). Kidney 119 71 57 34 Figure 3 shows the 12 most Ovary 192 common cancers for men and women 114 (as number of new cases), in the less 1000 800 600 400 200 0 200 400 600 800 1000 and more developed regions of the (Thousands) world. Developed countries comprise those of North America, Europe Figure 2. Estimated numbers of new cases (incidence) and deaths (mortality), by sex and site. (including the former USSR), Australia/New Zealand, and Japan; less developed countries The highest rates are in North America and in northwestern are the remainder. Europe, with moderate rates in Australia, New Zealand, and Figure 4 shows the most prevalent cancers, in men and China. women, together with the number of annual new cases at the National incidence rates closely reflect the history of same site. In terms of prevalence, the most common cancers tobacco smoking.20 The proportion of cases of lung cancer are breast (17.2%), colorectal (10.6%) and prostate (6.9%). caused by tobacco smoking has been estimated by comparing The ratio between prevalence and incidence is an indicator of observed incidence in different areas with incidence rates in prognosis; thus breast cancer is the most prevalent cancer in non-smokers from several large cohort studies.21 In 1990, the world, although there are less new cases than for stomach 86% of cases in men and 49% in women were estimated to be (for women) or lung cancer, for which the outlook is caused by smoking, although there was much regional considerably poorer. variation. Thus, in countries and regions with a long history A summary of global patterns and trends for the eight of smoking, about 90% of cases in men are related to most common cancers follows. tobacco, whereas the fraction is much lower in Africa and southern Asia. The proportions are more variable in women, Lung cancer even in Europe where they range from 80% in UK to virtually This is the most common cancer in the world, both in terms nil in Spain and Portugal, where incidence rates are the same of incidence (1.2 million new cases or 12.3% of the world as in non-smoking women in the USA and Japan. total) and mortality (1.1 million deaths or 17.8% of the Trends in lung-cancer incidence and mortality reflect the total); 52% of new cases occur in more developed countries. maturity of the smoking epidemic in different countries.22,23 It is by far the most common cancer of men worldwide with Our estimate of the numbers of cases worldwide has the highest rates observed in North America, Europe increased by 20% since 1990 (17% in men and 27% in (especially eastern Europe), South America, and women). This overall upward trend disguises substantial Australia/New Zealand. Moderately high rates are also seen differences between countries. In men, several populations in parts of eastern Asia. In less developed countries the have now passed the peak of the tobacco-related epidemic, highest rates are seen in the Middle East, China, the and incidence and mortality rates are now decreasing, such as Caribbean, South Africa, Zimbabwe, and the Pacific. In in the USA and the countries of northern and western women, incidence rates are lower (overall, the rate is 11.1 per Europe. In contrast, incidence and mortality rates are 100 000 in women compared with 34.9 per 100 000 in men). increasing rapidly in southern and eastern European THE LANCET Oncology Vol 2 September 2001 535 For personal use. Only reproduce with permission from The Lancet Publishing Group.
  • Review Global cancer statistics Men More developed Less developed Lung 471 430 Stomach 208 350 Prostate 416 127 Colon/Rectum 319 180 Liver 73 325 Oesophagus 55 224 Bladder 164 96 Non-Hodgkin 80 86 lymphoma Oral cavity 60 110 Leukaemia 58 86 Larynx 62 80 Kidney 79 39 600 500 400 300 200 100 0 100 200 300 400 500 600 (Thousands) Total 2 504 000 2 814 000 Women More developed Less developed Breast 579 471 Cervix uteri 91 379 Colon/Rectum 292 154 Stomach 125 193 Lung 175 142 Ovary 91 101 Corpus uteri 114 75 Liver 34 132 Oesophagus 16 117 Non-Hodgkin 66 55 lymphoma Leukaemia 47 65 Pancreas 61 39 600 500 400 300 200 100 0 100 200 300 400 500 600 (Thousands) Total 2 176 000 2 562 000 Figure 3. Estimated numbers of new cases in more developed and less developed countries. The 12 most common cancers in each sex are shown. 536 THE LANCET Oncology Vol 2 September 2001 For personal use. Only reproduce with permission from The Lancet Publishing Group.
  • Global cancer statistics Review countries. In women, the ‘epidemic’ is less advanced; most western countries Men Women show a rising trend in incidence and 3860 mortality, and in many less developed Breast 1050 countries (where smoking in women is Colon/Rectum 1245 1134 generally rare), there is little change in 449 446 risk. A few countries, where prevalence of smoking in women is declining, Prostate 1555 543 already show decreasing rates in younger women. Cervix uteri 1401 471 Breast cancer Stomach 902 496 This is the second most frequent 558 318 cancer in the world (1.05 million 1013 381 Lung cases), and is by far the most common 902 337 malignant disease in women (22% of Bladder 779 221 all new cancer cases). Worldwide, the 76 260 ratio of mortality to incidence is about 36%. Because of this relatively Corpus uteri 716 189 favourable prognosis, breast cancer Prevalence ranks fifth as a cause of death from Oral cavity 451 256 cancer overall (although it is the 170 97 Incidence leading cause of cancer mortality in 381 291 Non-Hodgkin women – the 370 000 annual deaths lymphoma 167 121 represent 13.9% of cancer deaths in women). Breast cancer is the most 4000 3000 2000 1000 0 1000 2000 3000 4000 (Thousands) prevalent cancer in the world today; there are an estimated 3.9 million Figure 4. Estimated numbers of new cases (incidence) and prevalent cases (alive within 5 years of women alive who have had breast diagnosis), by sex, and site. cancer diagnosed within the past 5 years (compared with just 1.4 million survivors – men or 1.5% annually. However, many low-risk countries are women – from lung cancer). recording increases much greater than this: 2% annually in Incidence rates are high in all more developed countries Japan, for example, and cancer registries in China are except Japan, with the highest age-standardised incidence in recording annual increases in incidence of 3–5%. Trends in the Netherlands (91.6 per 100 000) and the USA (91.4 per mortality from breast cancer are less straightforward, and in 100 000) (Figure 5). High rates are also observed in southern many countries there is evidence of a decrease in death rates South America, especially in Uruguay and Argentina. In in recent years. This was first remarked on in the USA,27 but it contrast, most African and Asian populations have low rates is also evident in Canada and in some European countries, eg of breast cancer, although these are increasing. In some Asian the UK, Netherlands, Denmark, and Norway.28 These populations rates are already the same as in southern Europe, changes probably reflect improvements in treatment and in some cases, such as the Philippines, rates are even (and therefore, improved survival), as well as earlier higher. diagnosis, due to both screening programmes and to better Prevalence of carriers of the major susceptibility genes awareness of breast cancer and the early signs of the disease (BRCA1 and BRCA2) in the general population is low and in women.29 the variation observed between populations can explain only some of the observed international and interethnic variation Colorectal cancers in incidence. Most breast cancer is due to environment and These cancers rank third in frequency of incidence (945 000 lifestyle factors, as illustrated by the striking changes in risk new cases, 9.4% of the world total) and mortality (492 000 that follow migration; for example, a rise in risk of breast deaths, 7.9% of the total), with similar numbers in men and cancer occurs in migrants to Australia from European women (ratio 1.1 to 1). The relatively good prognosis means countries at relatively low risk (Italy, Poland), particularly that colorectal cancer is the second most prevalent cancer in when migration takes place in childhood.24,25 Studies the world after breast cancer, with an estimated 2.4 million comparing the risks in migrants and their offspring, people alive with the disease diagnosed in the previous 5 particularly among Asians migrating to the USA, show major years (Figure 4). increases in risk between first, second, and third The incidence of large-bowel cancer is high in North generations.26 America, western Europe, Australia/New Zealand, and Incidence rates of breast cancer are increasing in most southern South America, and low in Africa and Asia. The countries, and the changes are usually greatest where rates geographic distribution of colon cancer and rectal cancer is were previously low. Since our previous estimates for 1990, similar, although the variation between countries is less for there has been an overall increase in incidence rates of about rectum than for colon. Thus, in high-risk populations, the THE LANCET Oncology Vol 2 September 2001 537 For personal use. Only reproduce with permission from The Lancet Publishing Group.
  • Review Global cancer statistics Figure 5. Estimated age standardised by world standard incidence rates, by country: breast cancer. ratio of colon to rectum is 2 to 1 or more (rather more in practised since the 1960s; elsewhere – USA10, Europe11, and women), in low-risk countries, rates are similar and there is China12 – it is generally in the range 20–25%. even a slight excess of rectal cancer in India). The difference in incidence between countries is assumed These large geographic differences probably represent the to be related to dietary factors, which certainly influence effects of different environmental exposures, presumably individual risk in epidemiological studies. Their importance mainly dietary. It has long been evident from migrant studies is consistent with the descriptive data, and studies of that the risk of colon cancer is quite labile to environmental migrants. In 1994, the International Agency for Research on change.30,31 Now, the rates in US Japanese – at least for colon Cancer classified infection with Helicobacter pylori as cancer – exceed those in the white population. carcinogenic to human beings,34 although its action is Incidence rates have been increasing in countries where probably indirect, by provoking gastritis, a precursor of they were previously low, whereas in high-risk countries, gastric atrophy, metaplasia, and dysplasia. On the basis of there has been stabilisation or decrease in incidence, prospective (cohort) studies, the relative risk conferred by H particularly in the younger age groups. For mortality, the pylori infection is about 2.5.35 The proportion of the pattern is similar, with an increase for countries with a low population infected is large in less developed countries initial rate (eastern Europe, Japan, and Singapore), small (80–90%); in more developed countries, the prevalence is increases or stable rates in countries with moderate rates, and lower (about 50%). With these values, H pylori would a decrease for high-rate populations (western Europe, North account for half of the world total for these cancers (55% in America).32,33 less developed countries, and 42% elsewhere). Dietary and other exogenous factors probably have a synergistic or Stomach cancer antagonistic role.36 Stomach cancer is the fourth most frequent cancer, with Incidence and mortality of gastric cancer have been 876 000 new cases (8.7% of the total) and 647 000 deaths decreasing in most countries. Our estimated incidence rates (10.4% of cancer deaths) in 2000. Almost two-thirds of these in 2000 were about 11% lower than those for 1990.8 This cases occured in less developed countries. Age-standardised decrease may be related to improvements in preservation and incidence rates are highest in Japan (69.2 per 100 000 in men, storage of foods; it may also represent changes in the 28.6 per 100 000 in women). High rates are also present in prevalence of H pylori by birth cohort, perhaps as a result of both sexes in eastern Asia, eastern Europe, and Central and reduced transmission in childhood, after improved hygiene South America. The rates are low in eastern and northern and reduction of crowding. In contrast to the overall Africa, North America, and southern Asia. Survival for decreasing trend, there has been an increase in cancers stomach cancer is moderately good only in Japan (52%), localised to the cardia, and this is evident in several where mass screening by photofluoroscopy has been populations.37,38 The reasons for this increase are not known; 538 THE LANCET Oncology Vol 2 September 2001 For personal use. Only reproduce with permission from The Lancet Publishing Group.
  • Global cancer statistics Review they parallel the increased prevalence of Barrett’s oesophagus per 100 000 in Scandinavia, and 76 per 100 000 in Australia and adenocarcinoma of the lower third of the oesophagus. (probably for the same reason). Mortality is affected by survival, and survival is Liver cancer significantly better in high-risk countries (80% in the USA This is the fifth most important cancer worldwide (564 000 versus 40% in less developed countries), but much of this is a or 5.6% of new cancer cases) but, because of the very poor consequence of latent cancer being detected by screening prognosis, the number of deaths is almost the same procedures. As a result, mortality rates are probably a better (549 000), and it is the third most common cause of death guide to the risk of invasive prostate cancer in different from cancer; 81% of cases occur in the less developed populations. Mortality rates are high in northern and western countries (with 54% in China). The highest incidence rates Europe, Australia/New Zealand, the Caribbean and North are in western and central Africa (where it accounts for and South America, and also in much of sub-Saharan Africa. almost a quarter of cancer in men), eastern and southeastern Mortality rates are low in Asian populations, and in northern Asia, and in Melanesia. Incidence is low in most developed Africa. The difference in incidence between China and the countries, except for Japan, and a moderately increased USA is about 60-fold and about 18-fold for mortality. incidence in some southern European countries. Migrants from low-risk countries, such as Japan, to areas Most liver cancers are hepatocellular carcinomas. The of higher risk, such as the USA, show large increases in major risk factors for this type are chronic infection with the incidence. Some of this change reflects an elimination of the hepatitis viruses, hepatitis B and C, both of which increase diagnostic bias influencing the international incidence rates, the risk of liver cancer about 20-fold.39 Because hepatitis B but it is almost certainly due partly to changes in virus is more common, the prevalence of chronic infection environment, possibly including diet. Nevertheless, the worldwide largely explains the patterns of liver cancer. The interethnic variations in incidence observed within countries exception is Japan, where prevalence of infection is low, – such as between whites, blacks, and Asians in the USA – but where the generations most at risk of liver cancer imply that there are important genetic determinants of risk, have a relatively high rate of infection with hepatitis and that the prevalence of the relevant genes differs between C virus.40 More than 75% of cases worldwide, and 85% of populations. Polymorphisms in genes controlling androgen cases in less developed countries, are caused by these two metabolism seem to provide at least part of the explanation.43 viruses.41 There has been a rapid increase in the incidence of Exposure to aflatoxins is probably also an important prostate cancer over the past 15 years – about 1.7% annual contributor to the high incidence of liver cancer in tropical increase worldwide. A review of international trends in areas of the world, where contamination of food grains with incidence and mortality44 shows the greatest increases in the fungus Aspergillus fumigatus is common. There is a incidence, especially in younger men, in high-risk countries, multiplicative interaction between aflatoxin exposure and probably partly because of the effect of increasing detection chronic infection with hepatitis B virus, suggesting that the of latent cancers after transurethral resection of the prostate, carcinogenic mechanisms differ. and, more recently, by screening for prostate-specific Cholangiocarcinoma, a tumour of the epithelium of the antigen. In the USA, the burden of prevalent latent cancers in intrahepatic bile ducts, comprises 10–25% of liver cancers in the subset of the population reached by opportunistic men in Europe and North America, and a much greater screening seems exhausted and incidence began to decrease proportion in women. The incidence shows little in the USA after 1992.45 Similar trends have been reported in international variation, with rates in men between 0.5 and Canada,46 the UK,47 France,48 Australia,49 and the 2.0 per 100 000, and lower rates in women.42 However, the Netherlands,50 although, in general, they are less striking. incidence is much higher in some localised areas, where Since 1992 in white men, and since 1994 in black men, infection with liver flukes is common, such as northeast mortality rates have begun to fall in the USA. There is much Thailand. debate as to whether this is the consequence of screening.51–53 Mortality and incidence in low-risk countries have also Prostate cancer increased: 104% in Chinese in Singapore, 84% in Miyagi, With 543 000 new cases, prostate cancer is the sixth most Japan, 55% in Hong Kong, and 44% in Shanghai, China, common cancer in the world, and third in importance in between 1975 and 1990.43 Although some of this change may men (10.2% of new cancer cases – 16.6% in more developed relate to better detection and diagnosis, much of it probably countries and 4.5% in less developed countries). The relates to westernisation of lifestyles, with increasing obesity prognosis is relatively good, so it is a less prominent cause of and changes in diet, ie increased consumption of meat mortality, with 204 000 deaths (5.8% of cancer deaths in and fat. men, 3.3% of all cancer deaths). The estimated prevalence in 2000 was 1.6 million. More than any other cancer, this is a Cervical cancer malignant disease of the elderly – 78% cases are in men over This is the second most common cancer in women age 65. worldwide (471 000 annual cases, 233 000 deaths). Almost Incidence rates are now influenced by the diagnosis of 80% cases occur in less developed countries, where cervical latent cancers by screening of symptom-free individuals, so cancer accounts for 15% of cancer in women, with a lifetime that where screening is common, incidence may be very high. risk of about 2%. In more developed countries it accounts for For example, it is 104 per 100 000 in the USA, where it is now only 4.2% of new cancers, with a lifetime risk of 1%. The by far the most commonly diagnosed cancer in men, 65–75 highest incidence rates are observed in Latin America and the THE LANCET Oncology Vol 2 September 2001 539 For personal use. Only reproduce with permission from The Lancet Publishing Group.
  • Review Global cancer statistics Figure 6. Estimated age standardised by world standard incidence rates, by country: cancer of the cervix uteri. Caribbean, sub-Saharan Africa, and south and southeast Asia Oesophageal cancer (Figure 6). In more developed countries, incidence rates are This is the eighth most common cancer worldwide, causing generally low, probably because of screening, with age- 412 000 new cases (4.1% of the total), and 338 000 deaths. standardised rates less than 14 per 100 000. Very low rates are Geographical variation in incidence is very striking. The also observed in China and in western Asia. highest risk areas of the world are in the Asian ‘oesophageal Human papillomavirus (HPV) is now accepted to be the cancer belt’ (stretching from northern Iran through the most important cause of cervical cancer.54 Case-control central Asian republics to north-central China), with studies suggest a very high risk associated with viral presence incidence rates as high as 200 per 100 000. High rates are also in middle age. With sensitive detection techniques, HPV is present in parts of east and southeast Africa, eastern South found in virtually all cervical cancers, and might, therefore, America, and certain parts of western Europe (especially be considered a necessary cause.55 Recent data from France and Switzerland). For women, the pattern is much the population surveys suggest that there is a correlation between same, with the Indian subcontinent added to the high- prevalence of HPV infection in the female population and ranking areas. Oesophageal cancer is more common in men incidence of cervical cancer.56 Other cofactors, such as parity than in women in most areas – the sex ratio is 6.5 in France and contraceptives, probably modify the risk in women for example, although in the high-risk areas of Asia and infected with HPV. Africa the sex ratio is much closer to unity. Incidence and mortality in cervical cancer have decreased There are also striking variations in incidence within quite substantially, particularly in more developed countries, countries in the high-risk areas. These represent exposures to where there are long-standing screening programmes. important carcinogens, but it seems that these are quite Decreases are also seen in some less developed countries, different in the various high-risk areas.49 Tobacco and alcohol particularly in China where the estimated age-standardised are the main agents involved in Europe and North America, incidence rate in 2000 was 5.2, compared with an estimated where over 90% of cases can be attributed to these causes. 17.8 in 1985.57 Although some of the differences reflect Chewing tobacco and betel are important carcinogens in the changing data sources, cancer-registry results also indicate a Indian subcontinent. Hot beverages have been shown to fairly dramatic decrease in rates in recent years.58 As a result of increase risk, and drinking hot maté is probably the cause of these trends, cervical cancer has ceded its place as the leading raised rates in Uruguay, southern Brazil, and northern cancer in less developed countries to breast cancer, and only Argentina. Nutritional deficiencies (specifically of in sub-Saharan Africa, Central America, south-central Asia, micronutrients) are thought to underlie the high risk in and Melanesia is it now the main cancer of women. central Asia, China, and southern Africa. Here other factors 540 THE LANCET Oncology Vol 2 September 2001 For personal use. Only reproduce with permission from The Lancet Publishing Group.
  • Global cancer statistics Review such as pickled vegetables, nitrosamine-rich foods, and Table 1. Estimated (2000) and projected numbers of cancer cases mycotoxins may also be involved, as well as consumption of opium residues (in Iran) or pipe-stem residues (in the The number of new cases (millions) of all cancers Transkei of southern Africa). Region 2000 2010 2020 2050 World 10.06 12.34 15.35 23.83 The future More developed regions 4.68 5.31 6.03 6.79 Future cancer burden can be projected from trends of Less developed regions 5.38 7.03 9.32 17.04 incidence and mortality in the past. Our estimates for 2000 Africa 0.3 0.79 1.04 2.53 did not incorporate any assumptions about existing trends. Asia (Japan) 0.52 0.61 0.67 0.65 Prediction of future patterns is even more difficult. For one Asia (other) 3.94 5.17 6.75 10.74 thing, projections based on historical patterns are not always Europe 2.77 3.06 3.36 3.64 a sound basis for future predictions. There can be quite South America 0.83 1.10 1.48 28.81 abrupt changes in trends in incidence and/or mortality with North America 1.38 1.65 2.03 2.61 the development of successful early detection or new forms of treatment, as described above for cancers of the prostate, Oceania 0.11 0.13 0.16 0.24 breast, and cervix. It is hard to foresee what further changes of this type will occur in the next decade, let alone in the next 50 years. Even preparing projections on a world scale is estimated incidence rates to the population projections difficult. Past trends varied widely in different world regions, specific for age and sex in 2010, 2020, and 2050. Table 1 and in many cases the trends have been in opposite shows the predicted number of new cases of cancer in the directions in different age groups (or birth cohorts) within major world regions at these dates. With current rates, the the past decade, such as lung cancer or colorectal cancers. For 10.1 million cases in 2000 will increase by 25% in each of the much of the world, we do not have enough information on two decades that follow, and by 2050, the number of new the evolution of age-specific incidence and mortality to make cancers will be nearly 24 million. The number of cancer a comprehensive set of projections. deaths will also rise, from 6.2 million in 2000, to 10 million On the other hand, it is easy to predict the effects of by 2020, and to 16 million in 2050. demographic change – population growth and ageing – on In 2000 there were slightly more new cancer cases (53%) cancer burden in the next few decades. This is because cancer and deaths (57%) occurring in less developed than in more affects the older age groups, and prediction of the numbers of developed countries. Since the biggest changes in the people in these age groups in the next few decades is quite demography of the world in the next 50 years will take place straightforward, since it demands no assumptions about in less developed areas, more and more of the future cancer future fertility patterns. burden will be in these regions. By 2020, population In 2000, the world population was estimated at around projections suggest that some 9 million new cases will occur 6 billion, and, with a projected increase of nearly 80 million in less developed countries compared with 6 million in more people a year, it will reach about 7.5 billion by 2020, and developed regions; by 2050, the burden will be over 17 8.9 billion by 2050.14 Growth rates are much lower in more million and 7 million new cases in less and more developed developed countries than in less developed countries, and areas, respectively. will be negative in most by the middle of next century. As a Population ageing means that an increasing proportion result, population size will peak in more developed countries of cancers will develop in the elderly in both more and less in about 2020 and then decrease – by 2050 the overall developed areas. In 2000, 46% of cancers occurred in people population should be about 2% lower than the 2000 aged 65 or over (57% cases in more developed countries and estimate, and the percentage of the world population living 42% in less developed countries). This can be projected to in Europe and Northern America is projected to decrease rise to 57% of all cancers occurring in the elderly in 2050 from 17% to 11.5% during this period. In contrast, a 63% (71% in more developed countries, and 53% in less increase in the population of the less developed countries is developed countries). expected between 2000 and 2050. The expansion is These figures are based on current incidence and particularly evident in Africa – the population is forecast to mortality rates. Clearly, these will not be maintained in the double by 2030. future; incidence and mortality rates of the major cancers are The rapid increase in the absolute and relative numbers of constantly evolving, as described earlier. It is fairly certain elderly people was one of the principal characteristics of the world population in the 20th century, because of increasing life expectancy. In less developed countries, for example, life Search strategy and selection criteria expectancy was 41 years in the mid-1950s, and 64 years by The data published in this review are the work of the 2000; by 2020 it is forecast to be about 71 years. As a result, author, and the published articles explaining the methods the proportion of people over age 65 in less developed regions have been cited. Previous work on global estimates of is projected to increase from 5% in 2000 to 15% in 2050. In disease published since 1985 were identified in PubMed. more developed areas, the proportion of elderly people in Selected English-language articles from my personal 2000 (14%) is forecast to rise to over 25% by 2050. collection were used to explain observed patterns and time The impact of population increase and ageing in the next trends in the results. half century can be illustrated by applying the current THE LANCET Oncology Vol 2 September 2001 541 For personal use. Only reproduce with permission from The Lancet Publishing Group.
  • Review Global cancer statistics that stomach cancer rates will continue to decrease, whereas 24 Geddes M, Parkin DM, Khlat M, Balzi D, Buiatti E, Eds. Cancer in the increasing risk of prostate and breast cancer is likely to be Italian migrants populations. IARC Scientific Publication No 123. Lyon: IARC Press, 1993. maintained for some time. The decrease in lung cancer finally 25 Tyczynski J, Tarkowski W, Parkin DM, Zatonski W. Cancer being achieved in some countries will be offset by the current mortality among Polish migrants to Australia. Eur J Cancer 1994; increases in some countries of eastern Europe and, quite 30A, 478–84. 26 Ziegler RG, Hoover RN, Pike MC, et al. Migration patterns and probably, by future increases in many less developed breast cancer risk in Asian-American women. J Natl Cancer Inst countries. Nevertheless, these simple projections illustrate the 1993; 85: 1819–27. increasing toll that cancer will take in our ageing world 27 Blot WJ, Fraumeni JF. Trends in esophageal cancer mortality among US blacks and whites. Am J Public Health 1987; 77: 296–98. populations, and highlight the need to seek and apply 28 Hermon G, Beral V. Breast cancer mortality rates are levelling off or effective preventive measure, as well as to strive for continued beginning to decrease in many western countries: analysis of time improvements in the effectiveness of treatment. trends, age – cohort and age – period models of breast cancer mortality in 20 countries. Br J Cancer 1996; 73: 955–60. 29 Blanks RG, Moss SM, McGahan CE, et al. Effect of NHS breast screening programme on mortality from breast cancer in England References and Wales, 1990–1998: comparison of observed with predicted 1 United Nations Development Programme (UNDP). Human mortality. BMJ 2000; 321: 665–69. development report 2000. Oxford: Oxford University Press, 2000. 30 Haenszel W, Kurihara M. Studies of Japanese migrants. I Mortality 2 United Nations Environment Programme. 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