Radiotherapy presentation

1. CANCER RADIOTHERAPY
Moderator: Dr Sandeep Bhattarai
Dr Manoj Bhandari
Resident year 1

2. CONTENTS:
• History and introduction
• Types of radiation decay
• Radiation components
• Law and mechanism of radioactivity
• Types of radiotherapy
• Radioisotopes
• Radiosensative and radioresistant tumors

4. Introduction:
• Conventional unit: Curie
• SI unit: Becquerel
• Bragg’s peak: seen in heavy
Charged particles like alpha and
Protons.𝑑𝑜𝑠𝑒α
1
velocity
in tissue

5. Radioactivity and decays:
• Act of emitting radiation spontaneously from a nuclei= radioactivity
• Unstable nucleus emits radiation and disintegrates into smaller stable
nucleus
• This process is k/a decay

6. Types of decays:
Atomic mass: decreases by
4
Atomic number: decreases
by 2

7. Beta and gamma decay:
Image A Image B

8. Components:
Alpha Beta Xray Gamma
Max: i/d power Less Lesser Least
Least penetrating More than alpha More than beta Maximum
Most commonly used in RT is Xray

9. Law of radioactivity:
•
𝐷𝑁
𝑑𝑡
= −𝜆𝑁,
• DN/dt= velocity of disintegration, 𝜆= radioactivity disintegration
constant.
• I=1/d^2 (inverse square law)
• Background radiation?

10. MECHANISM OF RADIATION:
Indirect method: most common, radiation interacts
with water of tissue, produces free radicals which
break DsDNA
Direct method: directly acts on dsDNA and breaks
DNA
Maximum radiosensitivity of a cell: G2/M junction
or M phase
Minimum: S phase

11. Fractionated radiotherapy:
• The total dose is split into many fractions and is given one after another on different
settings.
Why fractionated RT?
• Single large dose damages both normal as well as tumor cells
• Some cells in g2/m and some in s/g2/g1: some get destructed some survive
• Surviving fraction2 (SF2): survival of tumor cells after a radiation dose, inversely
related to radiosensitivity
• Components of Fractionated RT:
• Repair/recovery
• Repopulation
• Reoxygenation
• Re assortment

12. Types of FRT:
Conventional Hyper
fractionation
Hypo
fractionation
CHART
Most common - - -
1 fraction
(2Gy)/day, 2 days
off
>1 (1-1.2Gy)/day
usually 3
<5/week 1-2Gy BD/week
for 4-6 weeks
Used in
seminoma,
prostate ca,
lymphoma
Used in cerebral
gliomas, SCLC, HN
tumors
Used as palliative,
melanomas, soft
tissue sarcomas
Adenocarcinoma
lungs

13. Other types of RT:
Based on aim of treatment:
• Curative (early Hodgkin’s, Nasopharyngeal CA)
• Prophylactic(whole body irradiation in ALL, SCLC)
• Palliative (brain/bone mets)
Based on time:
• Neo adjuvant: used preoperatively
• Adjuvant: used post operatively
• Chemo radiotherapy

14. Based on modes of delivery:
EBRT/teletherapy:
• Mc type, tele=distance,
• 3 types: high voltage (40-500kv), super voltage (500-1000kv), megavoltage(1 mega
volt or higher)
• Uses Co 60 as radioisotope (artificial), t1/2= 5.2 yrs
LINACS(linear accelerators):
• Modified X-ray tubes
• Electrons are accelerated greater than X ray tubes
• Very high energy x rays are produced

15. Brachytherapy:
• Radiation source placed inside body (into the tumor)
• Advantage: minimal/no exposure to normal tissues
Types:
• Interstitial: used in prostate CA
Empty shells are placed inside prostate manually
Radioactive beads are then placed inside the shells using remote after loading equipment
• Intra cavitary: used in cervical CA
• Mold: used in superficial tumors (penile, CA of nail bed/finger)

17. Radioisotopes used:
Permanent (short half life) Temporary (long half life)
Cesium 131 Cesium 137
Gold 198 Cobalt 60
Radon 222 Iridium 192
Iodine 125 Tantalum
Yittrium Californium

18. Systemic RT:
• Radioactive material is injected IV
• Eg: I-131 for papillary thyroid CA
• P-32 in polycythemia rubra vera
• Samarium 132/strontium 89 in painful bony mets

19. Radiotherapy: special applications/recent advancements
• Intraoperative RT (IORT):
Irradiation of tumor bed immediately after tumor excision
10-20 Gy of radiation dose in a single session
Used in: pancreatic, gastric, colorectal, head neck CA
Team consist of surgeon, radiation oncologist, medical physicist, anesthesiologist,
pathologist and radiation therapist
3 different radiation modalities can be used:
Orthovoltage X-rays
Megavoltage electron beams (best)
HDR Ir192 brachytherapy sources

20. • Most IORT use megavoltage electron beams due to:
Electron beams deposited over a definite range, sparing normal tissues
Dose can be adjusted depending on target thickness and electron energy
STEREOTACTIC IRRADIATION:
Stereotactic=accurate localization using 3D CT/MRI
Dose in the order of 10-50 Gy; target small usually with a volume of 1-35cm3
the dose is given in fractions
2 types:
• SEBI (sterotactic external beam irradiation)- more commonly used
• Stereotactic brachytherapy

21. Equipment used:
Stereotactic frames (lekshell frames)
Imaging (CT, MRI, DSA)
Target localizing software: determines/localizes target along with frames
Stereotactic radiosurgery: total dose delivered in single session

22. Used in :
AVM
Trigeminal neuralgia
Schwannoma
Pituitary adenoma
Lars lekshell

23. • Gamma knife radiosurgery:
Uses 201 Co60 sources producing 201collimated beams directed to single focal
point
Source to focus distance: 40cm
Mostly used for brain tumors

24. • 3D conformal RT:
Target localization is achieved by imaging (3D CT,MRI, SPECT, PET, USG)
Uses multileaf collimators (20-60 pairs of tungsten leaves, width of 5-10mm and is
computer controlled)
Size and shape of radiation beam matches with the tumor
IMRT:
A form of conformal RT, also uses multi leaf collimators
Has increased tumor controlled probability and decreased treatment morbidity
Mc use in prostate CA
Not used in tissues that move with respiration eg: lung
Form of high precision RT

26. Boron neutron capture therapy:
• Boron is given IV
• Selectively taken by brain cells
• Irradiate with neutron beam
• Boron interacts with neutron
• Disintegrates into lithium
• Alpha particle released

27. Chemical modifiers:
• Radiosensitizers:
cause fixation of free radicals, exacerbate damage, minimize cell repair
2 types:
Hypoxic cell sensitizers:
mimic effect of Oxygen thus producing free radicals
Eg : metro/misonidazoles, hyperbaric o2 therapy, cisplatin, actinomycin D, 5 FU,
bleomycin
Non hypoxic cell sensitizers:
exact mechanism not known
Eg: halogenated pyrimidines (BudR, IUdR)

28. • Radioprotectors:
Prevent free radical propagation preventing further genetic damage
Helps normal tissues to recover
Eg:
Thiophosphate compounds: cysteine, cysteamine
Amifostine
GM-CSF, zinc oxide, melatonin, pentoxifylline
Chlorhexidine
Potassium iodide

29. Radiotherapy in Common Surgical malignancies:
• Thyroid malignancies (PTC): if residual disease or mets present after surgery
Radio iodine ablation using I131 at a dose of 50-100 mCi
T1/2 : 7 days
Emits Beta rays
• Carcinoma of breast: indications include: positive LN, size>5 cm, After BCS, locally
advanced breast cancer
2 modalities:
Whole breast irradiation: whole breast, supra and infra clavicular fossa, internal
mammary LN
Duration: 25 days, dose: 50-55 GY, 1 fraction/day

30. • Accelerated partial breast irradiation(APBI): indications:
Age >50 yrs, T1 disease, node –ve, ER/PR +ve, unifocal tumor and no LVI
Duration:5 days, 2 settings/day, dose: 3-35 Gys
Colorectal cancers:
Combined chemoradiation is given. Total dose usually is 80 Gy with 3 fractions of 20-30
Gy. In long course each fraction is given at 2 weeks interval.
Usually given using endorectal treatment technique
Indications: LN positive, T3/T4 disease, metastasis
Usually given in the neoadjuvant setting as:
• Short course: 5-6 days of chemoradiation then surgery
• Long course: 5-6 weeks of chemoradiation then interval of 5-6 weeks followed by
surgery

31. • Testicular tumors: seminomas are highly radiosensitive.
RT (usually 20Gy) to regional LN (para-aortic) for seminoma stage IA and IB
RT to retroperitoneal LN for seminoma stage IIA and IIB
• For locally advanced prostate cancer:
If age<70 yrs, >10 yrs life span, G3-5: Brachytherapy (I123,palladium) at 68-70 Gy
If age>70 yrs, <10 yrs life span, G1-2: brachytherapy+– ADT(androgen deprivation
therapy)
For metastatic disease: strontium 89, radium 223 (alpha rays)

32. Complications of Radiotherapy:
Organs and systems Acute complications Long term complications
Skin and mucosa Mucositis
Pruritis , HSR, ulcers
Alopecia, telagiectasia
Trismus
Salivary glands Swelling and tenderness after
1st dose
Xerostomia, osteonecrosis
CNS Nausea, vomiting, headaches,
acute encephalopathy(rare)
CVD, motor neuron disease,
neurocognitive dysfunction
Lungs Cough,SOB, radiation
pneumonitis,
RLD
CVS Acute pericarditis, valvular
dysfunction
IHD, Coronary artery stenosis,
cardiomyopathies
GI Abdominal cramps, vomiting,
malabsorption
Strictures, fistulas, rectal
bleeding
GUT Dyuria, hematuria, incontinence Detrusor dysfunction, urge
incontinence, hydronephrosis

33. Radiation enteritis:
• Acute: 1-3 weeks; resolves by 2-6 weeks
Presents with colicky abdominal pain, nausea, diarrhoea, loss of appetite
• Chronic:18 months-6 yrs; upto 30 yrs
• Risks: dose>5000cGy; dose<4000cGY no risk
Previous h/o HTN DM, abdominal surgeries, concurrent chemo
Pthology: progressive obliterative arteritis, submucosal fibrosis, thrombosis
Prevention:
• Use modern imaging and RT techniques
• Reperiteonalization, omental transposition
• ACEi, statins, sucralfate, radioprotector: Amifostine

34. • Steroids, probiotics, glutamine have no role
• Glutathionine, vitamin A,E pentoxifylline are in experimental phase
• 1-2% need surgeries(obstruction, perforation, fistula)
• Bypass procedures, resection and anastomosis.

35. Radiation cystitis:
• Early: occurs within 12 months of RT
Findings: inflammation and fibrosis, perineural inflammation, ulceration
• Late: occurs after 12 months of RT
• Findings: luminal occlusion, vascular ectasia and necrosis
• Risks dose: >2Gy/fraction, total dose >60Gy

36. Presentation:
• Frequency, urgency, dysuria, hematuria
• Grading(acc to RTOG)
Grade 1
•Slight epithelial atrophy
•Minor telangiectasia (microscopic hematuria)
Grade 2
•Moderate frequency
•Generalized telangiectasia
•Intermittent macroscopic hematuria
Grade 3
•Severe frequency and dysuria
•Severe generalized telangiectasia (often with petechiae)
•Frequent hematuria
•Reduction in bladder capacity (<150 cc)
Grade 4
•Necrosis/contracted bladder (capacity <100 cc)
•Severe hemorrhagic cystitis

37. Management:
• Grade 1 and 2: treat only if pt is bothered by symptoms
• Grade 3 and higher: requires treatment
• For frequency and urgency: anticholinergics, phenazopyridine
• HBO therapy: stimulates angiogenesis, reverses effects of RT, can be used in
pregnancy, 100% O2 at 2-2.5 AtM for 90-120 mins
• Surgery done if: gross hematuria not responding to bladder irrigation, small
contracted UB with incontinence or severe frequency, fistulas, HDN, strctures
• Options:bladder augmentation, urinary diversion, cystectomy.

38. TABLE 10.8 Examples of malignancies that may be cured without the need for surgical excision.
Malignancy Potentially curative treatment
Leukaemia Chemotherapy (+/− Radiotherapy)
Lymphoma Chemotherapy (+/− Radiotherapy)
Small cell lung cancer Chemotherapy (+/− Radiotherapy)
Tumours of childhood (rhabdomyosarcoma,
Wilm’s tumour)
Chemotherapy (+/− Radiotherapy)
Early laryngeal cancer Radiotherapy
Advanced head and neck cancer
Chemo-radiation (synchronous chemotherapy
and radiotherapy)
Oesophageal cancer
Chemo-radiation (synchronous chemotherapy
and radiotherapy)
Squamous cell cancer of the anus
Chemo-radiation (synchronous chemotherapy
and radiotherapy)
Advanced cancer of the cervix Radiotherapy (+/− chemotherapy)
Medulloblastoma Radiotherapy (+/− chemotherapy)
Skin tumours (BCC, SCC) Radiotherapy

39. • Radiosensitive tumors:
Wilms tumor
Ewing’s sarcoma
Lymphoma
Multiple myeloma
Seminoma/dysgerminoma
• Radioresistant tumors:
Hepatic cell carcinoma
Pancreatic Carcinoma
RCC
Osteosarcoma
Melanoma

40. Take home points:
• The SI unit of radiation is Becquerel
• There are 3 main decays namely alpha, beta and gamma
• Fractionated RT is used today as compared to single large dose conventional RT
• The radiation causes tissue damage by producing free radicals and DsDNA breaks
• RT can be used before (neo adjuvant), intraop, postoperatively(adjuvant) surgery
• There are different tumors that are radiosensitive as well as radioresistant
• Different chemical modifiers can be used along with RT inorder to accelerate or
prevent tissue damage depending on the situation.

41. REFERENCES:
• Bailey and love’s short practice of surgery 27th edition
• Schwartz’s principles of surgery 11th edition
• Walter’s and millers textbook of radiotherapy 7th edition
• https://www.uptodate.com/
• https://www.medscape.com/
• https://www.astro.org/

42. THANKYOU!!