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The national lung screening trial /Nahid Sherbini
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  • 1. The National Lung Screening Trial: Overview and Study Design Nahid Sherbini Radiology. 2011 January; 258(1): 243-253.Published online 2011January. 10.1148/radiol.10091808
  • 2. Introduction • The National Lung Screening Trial (NLST) is a multicenter, randomized controlled trial (RCT) Comparing: Low-dose CT with--- CXR screening of current and former heavy smokers for lung cancer. This is the largest randomized study of lung cancer screening in a high-risk population to date.
  • 3. The Magnitude of the Lung Cancer Problem • Lung cancer deaths^ 25% of all cancer deaths • While smoking cessation reduces the elevated risk of lung cancer, former smokers remain at elevated risk relative to never smokers .
  • 4. Lung Cancer Screening • Clinical stage at diagnosis is a major determinant of survival after therapy .
  • 5. NLST Description/Design Overview • Started in Sep 2002 – April 04 • Cohort - 53,456 participants • Participant was randomized to: a baseline 2 annual screenings • By either low-dose CT OR CXR.
  • 6. Endpoints • The primary endpoint of the NLST is lung cancer mortality. • Secondary endpoints include all-cause mortality, incidence of lung cancer, lung cancer case survival (as measured from date of diagnosis), and lung cancer stage distribution.
  • 7. Sample Size Considerations • Estimated by using data from the Mayo Lung Project With 25000 participants enrolled in each of years 1 and 2 of the trial. • Statistical power of 90% for detecting a 21% reduction in lung cancer mortality in the low- dose CT arm relative to the CXR arm.
  • 8. Low-Dose CT Screening • Multidetector (ie, at least 4 detectors) whole chest scanned in a single maximal breath hold and to achieve good resolution. • Utilized a low radiation exposure protocol ( 2 mSv, compared with 7 mSv for a standard-dose diagnostic chest CT examination ) .
  • 9. Interpretations • Positive findings were defined as a noncalcified nodule ≥4 mm on CT scan or any noncalcified nodule on x-ray.
  • 10. Interpretations and Recommendations
  • 11. False Positive • CT 96.4% • CXR 94.5%
  • 12. Results
  • 13. Discussion • The NLST is the only has adequate statistical power to detect a modest reduction in lung cancer mortality . • The largest in Europe “ NELSON trial, randomized to low-dose CT or community care”. • NLST, is providing a definitive assessment of harms and benefits associated with low-dose CT screening.
  • 14. Interim Analysis in November 2010 • The trial was stopped after they found a statistically significant benefit for CT scanning. • At a median follow-up of 6.5 years
  • 15. Interim Analysis in November 2010 CT GROUP • 645 cases of lung cancer / 100,000 person • (1060 cancers) • 247 lung cancer deaths • Mortality reduction 20.0 % (95% CI 3.8-26.7). • All-cause mortality reduction 6.7 %(CI 1.2-13.6 percent) CXR GROUP • 572 cases / 100,000 person • (941 cancers) • 309 deaths
  • 16. Complication occurred • CT 1.4 % • CXR 1.6%
  • 17. MORE FINDINGS CT group • LESS stage IV cancers were observed. • Stage I or II (70 % of CT- detected and), except for small cell cancers that accounted for less than 10 % of detected cancers. • Chest CT identified a preponderance of adenocarcinomas. CXR group • 56.7 %detected
  • 18. Results
  • 19. In summary • CT screening reduced mortality in a high-risk population, compared to CXR . • The number needed to screen with low-dose CT to prevent one lung cancer death was 320 in the NLST. • Cost of screening per life saved is unknown but likely to be high. • The high (≈95%) false-positive rate leading to the need for additional studies, the need for ongoing screening. • Low absolute number of deaths prevented (73 per 100,000 person years).