Radiotherapy

Question 1

What are the two most curative treatments for all cancers?

Answer 1

Surgery and radiotherapy.

Question 2

What is the use of radioactive iodine (Iodine-131)?

Answer 2

Used to treat thyroid cancer and hyperthyroidism

Question 3

What drugs are required after using iodine-131 to treat thyroid cancer?

Answer 3

Because the thyroid is ablated patients need to take thyroid replacements.

Question 4

What are the three forms of radiation used to treat cancers?

Answer 4

Photons/Xrays, wave like packets of energy. Gamma rays emitted by radioactive decay (iodine-131)

Question 5

Which patients require general anesthesia when being treated with radiotherapy?

Answer 5

children younger than three or four.

Question 6

In which patients is it likely that they will have to have their mask refitted over the course of their treatment.

Answer 6

Patients with head and neck cancer. This is because it becomes very painful to swallow due to radiotherapeutic treatment of their cancer. They are particularly prone to weight loss, hence the mask stops fitting as well.

Question 7

If a patient was anticipated to experience weight loss over the course of their treatment, what could be given to them to prevent this weight loss, preventing the need to reconfigure their mask and radiotherapy etc

Answer 7

Feed them through a Peg tube (straight into the stomach/duodenum) to prevent weight loss.

Question 8

What critical organ will be damaged by full dose radiotherapy to the breast?

Answer 8

The lung

Question 9

If the internal mammary chain becomes irradiated, what is a likely consequence on a nearby critical organ?

Answer 9

The heart becomes irradiated which can increase the chance of heart disease by several percent.

Question 10

What radiotherapy would you use to minimise radiotherapy toxicity to the heart

Answer 10

Proton therapy as it is possible to stop the movement of the particle at a designed point (by modifying the energy the proton has)

Question 11

What can be the result of irradiating the eyes

Answer 11

Cataracts - but this can be easily treated.

Question 12

What other structures are irradiated when treating adenocarcinomas?

Answer 12

Lymph node chains are irradiated as this is the way that the primary tumour tends to spread.

Question 13

Which source of gamma rays is used most often for brachytherapy

Answer 13

Iridium-192

Question 14

What is the unit of absorbed dose?

Answer 14

Gray - 1Gy is the deposit of one joule of energy in one Kg of matter or tissue

Question 15

How long can the biological effects of radiotherapy last?

Answer 15

years

Question 16

What are the five R’s of radiobiology

Answer 16

1) Repair - mainly DSB repair
2) reoxygenation - irradiating the tumour gives a transient hypoxia
3) - Redistribution - Kill some of the cells but then other cells (stem) can move in and fill the space.
4) Radiosenstivity - Some cancers are very sensitive - lymphoma, testicular. Some are not sensitive
5) Repopulation - multiplication of redistributed tumour cells.

Question 17

How does radiotherapy enhance the effect of immunotherapy?

Answer 17

Causes immunogenic cell death, increased antigen cross presentation and increased activation of T cells.

Question 18

What dosage is required to see a synergistic effect with radiotherapy and immunotherapy

Answer 18

over 5Gy, normally 8

Question 19

How does the cyber knife overcome the movement of a tumour due to breathing etc during sterotactic body radiotherapy (SBRT)

Answer 19

Gold beads are placed around the tumour and the robot tracks the seeds and follows the motion of the target.

Question 20

What are 5 methods to manage motion during radiotherapy

Answer 20

Patient holds their breath, free breathing where the motion is tracked, Gating (the machine switches off when the target goes beyond a certain pre determined area, abdominal compression, tracking (gold seeds)

Question 21

What are the four benefits of giving a higher dose per fraction>

Answer 21

More convenient, Lower cost of treatment, Increased total dose that can be safely delivered, dose specific biological effects (vascular effects and immunological aspects

Question 22

What is an abscopal response?

Answer 22

Phenomenon in which local radiotherapy is associated with the regression of a metastatic cancer at a distance from the irradiated site.