283 - Radiation Oncology Flashcards
How does fractionating radiation allow for better cell kill and sparing of normal tissues?
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Spares normal tissue
- Allows normal tissue to repair itself, re-populate
- Often, malignant cells do not have these repair mechanisms
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Better cell kill
- Reassortment: Allows cells in radio-resistant phase to get to a more sensitive phase before the next tx
- Reoxygenation: Tumors that are hypoxic don’t respond as well; oxygenation is important for indirect killing (Ionizing radiaton -> free radical generation -> DNA damage)
What is the mechanism by which radiation induces a biologic eent?
- Direct (~1/3 of damage)
- Ionizing radiation causes DNA breaks
- Indirect (~2/3 of damage)
- Ionizing radiation generates free radicals, which cause DNA breaks
- Oxygen is important for this!
What is brachytherapy?
When is it indicated?
Focal delivery of a radioactive isotope via implant for the purpose of cancer therapy
Example: curative therapy in locally advanced cervical cancer
Thank you @Lauren Smith and PJDJ deck!
Vs. external beam = shooting x-rays or gamma rays at the tumor from an external source
What is “gamma knife” radiation?
When is it used?
Gama knife = stereotactic radiosurgery. Uses advanced image guidance
Used when there are small, well-defined targets (not for microscopic spread)
Often used for intra-cranial treatment (single fraction)