Radiation therapy EXAM LATEST VERSION EXAM COMPLETE QUESTIONS AND CORRECT DETAILED ANSWERS WITH RATIONALES| ALREADY GRADED A+

Radiation therapy EXAM LATEST VERSION EXAM COMPLETE QUESTIONS AND CORRECT DETAILED ANSWERS WITH RATIONALES| ALREADY GRADED A+ The 2 uses of ionizing radiation in cancer - Answer- 1. Curative treatment 2. Paliative treatment Goals of curative radiotherapy - Answer- - Sole treatment (rare) e.g isolated lymphosarcomas - Adjunctive treatment (usual) e.g mast cell tumours, sarcomas Goals of palliative radiotherapy - Answer- - Pain e.g inoperable osteosarcoma, spine - Physical obstruction e.g sub lumber lymph nodes - Neurological e.g lymphosarcomas Goal of radiotherapy - Answer- Radiation to kill cancer cells with minimal effect on the surrounding normal tissues. Is radiation local or systemic? - Answer- Radiation is a local therapy with no systemic effects. How does radiation kill cells? - Answer- Direct effect - DNA damage - this leads to cell death during cell division. Principle of radiation - Answer- X-rays, gamma rays or electons Works from outside of tumour inwards. Indirect effects of radiation - Answer- - Free radicals - Oxygen effect Free radicals associated with radiotherapy - Answer- - Ionization of water leads to free radicals - OH radical is very reactive and accounts for most of radiation damage. Oxygen effect - Answer- - High O2 fixes free radical damage to DNA - Cells separated from capillary bed 100um are hypoxic - Hypoxia protects cells from radiation damage - large tumours are less sensitive to radiation damage - Small tumours (less cells to kill) are more sensitive radiotherapy associated cell death - Answer- - Cycling death - Interphase death Cycling death - Answer- - Limited to dividing cells - Acheived at lower doses - Growth fraction and doubling time of cells important Interphase death - Answer- -Target cells that are not in mitosis - Resistant cels ultimately susceptible - High dose required - Special case = lymphoid tissue (low dose required). The two possible tissue responses to radiation therapy - Answer- -Acute responding tissues - Lte responding tissues. Acutely responding tissues - Answer- - Rapid cell proliferation - Effects develop immediately and are self-limiting Late responding tissues - Answer- - Slow rate of cell proliferation - Effects develop months to years after therapy. The unit of dose in radiotherapy - Answer- gray (Gy) 1 Gy - Answer- 1J of energy absorbed by 1kg tissue How is the dose in radiotherapy (Gy) usually recorded - Answer- centiGy 1Gy = 100cGy How is the total dose administered? - Answer- Fractioned over multiple treatments One radiation treatment is called... - Answer- Fraction What do radiation prescriptions include? - Answer- - Dose per fraction - The number of fractions e.g 3Gy x 19 fractions = 57Gy total dose 3 Types of radiation - Answer- - External beam radiation - Interstitial beam radiation - Systemic radiation therapy How is the type of radiation classified - Answer- According to the method of delivery What is external beam radiation also called? - Answer- Teletherapy What is interstitial beam radiation also called? - Answer- Brachytherapy Radiation type for external beam radiation (Teletherapy) - Answer- X-rays or gamma rays Radiation type for interstitial beam radiation (Brachytherapy) - Answer- Gamma or beta rays Radiation type for systemic radiation therapy - Answer- Gamma or beta rays Which type of radiation therapy is are gamma rays used in? - Answer- All of the (External, interstitial, systemic) Which type of radiation therapy are beta rays used in? - Answer- Interstitial Systemic Which type of radiation therapy are x-rays used in? - Answer- External ONLY What is the most common form of radiotherapy? - Answer- External radiotherapy (Teletherapy) Where is external radiotherapy targeted? - Answer- Non-radioactive patient Directed into the tumour Advantages of external radiation therapy orthovoltage - Answer- -Simlicity -Low cost -Shielding requirements External beam radiotherapy Orthovoltage - Answer- Low - medium energy range Disadvantages of external beam radiotherapy orthovoltage - Answer- - Penetration low - Maximum dose to skin - Increased absorption of dose in bone relative to soft tissue