1. PRINCIPLES OF RADIATION ONCOLOGY DR NWANKWO K. C.

2. Radiotherapy (XRT) is the use of ionizing radiation to treat disease.

3. radiation Transfer of energy from a source to space without the aid of a medium. Two types- –Electromagnetic (non particulate)- Xray, Gamma ray –Particulate – electrons, beta particles, protons, alpha particles, neutrons

4. HISTORY 1800: Infrared radiation by Hershel 1895: Xrays by Wilhelm Roentgen 1896: Natural radioactivity by Henri Becquerel 1898: Erythema, ulceration from uranium salt. 1900s: Bergonie & Tribondeau on radiosensitivity

5. BASIS OF RADIATION FOR THERAPY

6. IONIZATION-EXCITATION Energy

7. Chemical Changes following absorption of ionising radiation The living material is made up of 60 -70% water. When irradiated most of the absorbed energy will be taken up by water molecules H 2 O →H 2 O + + -e -e + H2O → H 2 O- H 2 O + → H + + OH* H 2 O- → H* + OH-

8. H* and OH* are free radicals. Free radicals are electrically neutral atoms or molecules having an unpaired electron in their outer orbits They are usually very reactive and very damaging Other radicals both free and radicals bound to organic molecules are formed

9. Biological Actions of Ionizing Radiation It causes damage directly to cellular DNA Indirectly through toxic-free radicals Single and double strand breaks Results in reproductive death of the cell Interphase death, apoptosis, cytolysis

10. Radiobiology - factors important in the response to radiation. 4 Rs Re-oxygenation Repair of sub-lethal damage Repopulation Redistributions & Reassortment along cell cycle phases

11. Fractionation Single large dose of radiation causes profound effect on normal tissues Multiple fractions caused desired effect on tumours and spares normal tissues

12. RADIOSENSITIVITY; biological factors The higher the cell division & less differentiated, the higher the radiosensitivity of the cell eg; bone marrow stem cells, mucosal cells, cancer Slowly dividing cells, non dividing and adult differentiated cells are relatively radioresistant eg; CNS cells, liver, muscle

13. Role of Radiotherapy Role of Radiotherapy One of the main treatment modalities for cancer (often in combination with chemotherapy and surgery) Generally 50 to 60% of cancer patients will benefit from radiotherapy Minor role in other diseases Siemens Oncology

14. Aim To kill ALL viable cancer cells To deliver as much dose as possible to the target while minimising the dose to surrounding healthy tissues target Patient Critical organs Beam directions

15. Major indications for radiotherapy Head and neck cancers Gynaecological cancers (e.g. Cervix) Prostate cancer Other pelvic malignancies (rectum, bladder) Adjuvant breast treatment Brain cancers Palliation

16. Components of a Radiotherapy Department Diagnostic facilities (CT, MRI, …) Simulator Mouldroom Treatment planning External beam treatment units Brachytherapy equipment Clinic rooms, beds,...

17. Professionals in radiotherapy Radiation oncologists Medical radiation physicists Radiation therapists Nursing staff Radiation safety officer Information technology officer Administrative staff

18. Approaches Palliative radiotherapy to reduce pain and address acute symptoms – e.g. bone metastasis, spinal cord compression,... Radical radiotherapy as primary modality for cure – e.g. head and neck Co-treatment in conjunction with surgery – e.g. breast cancer

19. Forms of Radiotherapy (Options for dose delivery) External beam radiotherapy = dose is delivered from outside the patient using X Rays or gamma rays or high energy electrons Brachytherapy = dose delivered from radioactive sources implanted in the patient close to the target (brachys = Greek for short distance

20. Teletherapy (External Beam Therapy) Most common form of XRT in clinical use. Beams of X- and gamma rays, high energy electrons and neutrons have all been used in this way. There are different types according to their energy. X-ray and Gamma rays are the most widely used.

21. Superficial Voltage X-ray Energy 50 – 150 KV Suitable for the treatment of superficial lesions Useful treatment energy penetrates to only about 1cm beneath surface

22. Superficial/orthovoltage unit

23. Image Gallery Radiation Therapy (Oncology) - External Beam Therapy

24. LINAC Installed in Radiotherapy Unit, UNTH Enugu

25. Linear accelerator with electron cone Electron applicator

26. Modern Cobalt 60 unit

27. Electron beams produced by LINAC. As most particulate radiation, they have a definite range in tissue with a sharp cut- off.

28. BRACHYTHERAPY Involves placing sealed radioactive sources very close or in contact with the target tissue Plesiotherapy (Mould treatment) Skin surface dose applications – consists of radioactive sources fixed in an applicator Intracavitory – placing of radioactive sources within a body cavity. e.g.. Intrauterine tubes and vaginal sources. Interstitial – surgically implanting small radioactive sources directly into the target tissues. Example – Cancer of tongue, lips, breast

29. Brachytherapy Low dose rate, LDR, (60Gy in about 5 days) and high dose rate, HDR, (several fractions of several Gy in few minutes each) applications

30. Intracavitory brachytherapy

31. Brachytherapy Interstitial implant for breast radiotherapy Intracavitary gynecological implant Seven 192-Ir wires Three 137-Cs sources

32. Interstitial brachytherapy

33. Example for HDR Brachytherapy

34. Interstitial brachytherapy Radioactive seeds

35. Sources of Radiation Radium -226 Cobalt 60 Caesium – 137 Iridium -192 Gold – 198 Handling Procedure –Direct handling of live sources, e.g Iridium wire, hairpins typically into the tongue –Manual after loading – inactive source carriers are inserted initially –Remote after loading Placement of source carrier Source introduced by remote control

36. Involves the administration of a radioactive isotope systemically which is then selectively absorbed and concentrated in specific organs e.g. Radioiodine -131 for thyroid cancer. 32-P for polycythaemia vera, Strontium- 89 for bone metastases. Internal Isotope Treatment

37. Combined surgery and XRT To limit the extent of surgery Local control rates are better for large tumours (>5cm) than either modality alone

38. Preoperative radiotherapy -Reduce the chance of tumor implantation -Sterilize subclinical disease beyond resection margin -Sterilize lumph node metastasis outside operative field -Reduce tumor dissemination -Increase possibility of resectability

39. disadvantages Interferes with normal wound healing Patients may be irradiated unnecessarily Pathological features may be masked Surgery may be delayed

40. Postoperative irradiation Eliminate residual tumour Higher doses can be delivered Operative findings and pathology report may guide later XRT planning

41. disadvantages Delay in delivering XRT Response to XRT may be affected by postoperative vascular changes

42. Intraoperative radiotherapy Irradiation concentrated in a tumour while avoiding surgically mobilized normal tissue High radiation dose can be delivered For treating deep-seated cancers

43. Principles of Radiotherapy Treatment Planning Assessment and staging –Tumour volume –Target volume Patient positioning Immobilization- Perspex shells, casts,foam blocks, straps Tumour localization- inspection and palpation, simulator or CT scan Choice of treatment machine Dose specification and prescription Verification Treatment Treatment duration

44. Side Effects of XRT DETERMINISTIC, NON-STOCHASTIC Early Effects Non specific – Tiredness, anxiety, depression Specific –Skin – Erythema → desquamation –Bowel – Diarrhoea/colic –Bladder – frequency/dysuria –Scalp – Hair loss –Mouth/pharynx – mucositis

45. Oral sequelae of head & neck Radiotherapy Mucositis Hyposalivation/Xerostomia Taste loss Osteoradionecrosis Radiation caries Trismus.

46. Late Effects Usually seen after 6 months of therapy –Skin – fibrosis, telangiectasia, rarely necrosis –Bowel – stricture, perforation, bleeding, fistulae –Bladder – fibrosis → frequency, haematuria, fistulae –CNS – myelitis → paraplegia, cerebral necrosis –Lung – Fibrosis

47. WHOLE BODY IRRADIATION- Radiation Syndromes Bone Marrow Syndrome GIT Syndrome CNS Syndrome

48. NON-DETERMINISTIC STOCHASTIC Carcinogenesis Teratogenesis Hereditary Effects Genetic Effects Non-specific premature ageing

49. Summary Radiotherapy is an important cancer treatment modality Accuracy of dose delivery is essential for good outcomes The complex and high tech environment requires attention to quality assurance and radiation protection