Radiation Oncology

Question 1

Most radiosensitive cancers

Answer 1

Leukemias, most lymphomas and germ cell tumors. (impt distinction between radiosensitive and curable from radiation though)

Question 2

Moderately radiosensitive cancers

Answer 2

epithelial cancers

Question 3

Radioresistant cancers

Answer 3

RCC and melanoma

Question 4

Relation of tumor size t responsiveness to radiation therapy

Answer 4

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.

Question 5

Side effects of radiation for bony mets

Answer 5

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

Question 6

Main side effects of radiation therapy

Answer 6

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.

Question 7

radiation effect on cancer cells

Answer 7

Result of the ionization of water, forming free radicals, notably hydroxyl radicals, which then damage the DNA.

Question 8

why large tumors are less radiosensitive

Answer 8

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.

Question 9

unit for photon radiation therapy

Answer 9

greys (Gy)

Question 10

SUV in PET/CT means

Answer 10

standardized uptake value

Question 11

description of lesion on PET with high SUV

Answer 11

“hot”

Question 12

Dose of radiation for palliative treatment of bone mets

Answer 12

8 Gy, single fraction

Question 13

SRS means + mechanism

Answer 13

• stereotactic radiosurgery
• highly precise form of radiation therapy that treats each brain tumor with a single, targeted high-dose of radiation

Question 14

When response to XRT is typically seen

Answer 14

3-4 weeks

Question 15

When to image mass following XRT

Answer 15

4-6 weeks

Question 16

Number of sessions of SRS typically

Answer 16

usually 3-4 treatments

Question 17

Medication that has been shown to improve cognition

Answer 17

memantine

Question 18

Can you do SRS after WBRT?

Answer 18

YES

Question 19

General response timeframe to XRT and why

Answer 19

Can take weeks to see a response to tumor volume s

Question 20

What is cyber knife for prostate? Fractions?

Answer 20

Basically SBRT for prostate, 5 fractions

Question 21

How does SRS work?

Answer 21

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.

Question 22

How is SRT different than SRS?

Answer 22

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

Question 23

SRT is what?

Answer 23

stereotactic radiotherapy