Radiation Oncology Flashcards
Most radiosensitive cancers
Leukemias, most lymphomas and germ cell tumors. (impt distinction between radiosensitive and curable from radiation though)
Moderately radiosensitive cancers
epithelial cancers
Radioresistant cancers
RCC and melanoma
Relation of tumor size t responsiveness to radiation therapy
Very large tumors respond less well to radiation than smaller tumors or microscopic disease. This is why surgery or chemo is often performed prior to radiation.
Side effects of radiation for bony mets
Minimal or no side effects, although short-term pain flare-up can be experienced in the days following treatment due to oedema compressing nerves in the treated area
Main side effects of radiation therapy
Fatigue and skin irritation, like a mild to moderate sun burn. The fatigue often sets in during the middle of a course of treatment and can last for weeks after treatment ends. The irritated skin will heal, but may not be as elastic as it was before.
radiation effect on cancer cells
Result of the ionization of water, forming free radicals, notably hydroxyl radicals, which then damage the DNA.
why large tumors are less radiosensitive
Solid tumors can outgrow their blood supply, causing a low-oxygen state known as hypoxia. Oxygen is a potent radiosensitizer, increasing the effectiveness of a given dose of radiation by forming DNA-damaging free radicals. Tumor cells in a hypoxic environment may be as much as 2 to 3 times more resistant to radiation damage than those in a normal oxygen environment.
unit for photon radiation therapy
greys (Gy)
SUV in PET/CT means
standardized uptake value
description of lesion on PET with high SUV
“hot”
Dose of radiation for palliative treatment of bone mets
8 Gy, single fraction
SRS means + mechanism
- stereotactic radiosurgery
- highly precise form of radiation therapy that treats each brain tumor with a single, targeted high-dose of radiation
When response to XRT is typically seen
3-4 weeks
When to image mass following XRT
4-6 weeks
Number of sessions of SRS typically
usually 3-4 treatments
Medication that has been shown to improve cognition
memantine
Can you do SRS after WBRT?
YES
General response timeframe to XRT and why
Can take weeks to see a response to tumor volume s
What is cyber knife for prostate? Fractions?
Basically SBRT for prostate, 5 fractions
How does SRS work?
utilizes multiple convergent beams to deliver a high single dose of radiation to a radiographically discrete treatment volume, thereby minimizing radiation dose to adjacent structures.
How is SRT different than SRS?
SRT uses focused radiation in the same way as SRS but fractionates the radiation over a series of sessions. Fractionation improves normal tissue tolerance of radiation, and SRT may be a reasonable alternative for patients with surgically inaccessible lesions, either as postoperative therapy following subtotal resection, definitive treatment without any surgery, or treatment of recurrent disease [55,56].
SRT is generally used instead of SRS when there is concern for normal tissue injury, either because of larger tumor size or proximity to radiation-sensitive structures, most commonly the optic nerves or chiasm
SRT is what?
stereotactic radiotherapy
