Radiotherapy Flashcards
What are the two most curative treatments for all cancers?
Surgery and radiotherapy.
What is the use of radioactive iodine (Iodine-131)?
Used to treat thyroid cancer and hyperthyroidism
What drugs are required after using iodine-131 to treat thyroid cancer?
Because the thyroid is ablated patients need to take thyroid replacements.
What are the three forms of radiation used to treat cancers?
Photons/Xrays, wave like packets of energy. Gamma rays emitted by radioactive decay (iodine-131)
Which patients require general anesthesia when being treated with radiotherapy?
children younger than three or four.
In which patients is it likely that they will have to have their mask refitted over the course of their treatment.
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.
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
Feed them through a Peg tube (straight into the stomach/duodenum) to prevent weight loss.
What critical organ will be damaged by full dose radiotherapy to the breast?
The lung
If the internal mammary chain becomes irradiated, what is a likely consequence on a nearby critical organ?
The heart becomes irradiated which can increase the chance of heart disease by several percent.
What radiotherapy would you use to minimise radiotherapy toxicity to the heart
Proton therapy as it is possible to stop the movement of the particle at a designed point (by modifying the energy the proton has)
What can be the result of irradiating the eyes
Cataracts - but this can be easily treated.
What other structures are irradiated when treating adenocarcinomas?
Lymph node chains are irradiated as this is the way that the primary tumour tends to spread.
Which source of gamma rays is used most often for brachytherapy
Iridium-192
What is the unit of absorbed dose?
Gray - 1Gy is the deposit of one joule of energy in one Kg of matter or tissue
How long can the biological effects of radiotherapy last?
years
What are the five R’s of radiobiology
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.
How does radiotherapy enhance the effect of immunotherapy?
Causes immunogenic cell death, increased antigen cross presentation and increased activation of T cells.
What dosage is required to see a synergistic effect with radiotherapy and immunotherapy
over 5Gy, normally 8
How does the cyber knife overcome the movement of a tumour due to breathing etc during sterotactic body radiotherapy (SBRT)
Gold beads are placed around the tumour and the robot tracks the seeds and follows the motion of the target.
What are 5 methods to manage motion during radiotherapy
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)
What are the four benefits of giving a higher dose per fraction>
More convenient, Lower cost of treatment, Increased total dose that can be safely delivered, dose specific biological effects (vascular effects and immunological aspects
What is an abscopal response?
Phenomenon in which local radiotherapy is associated with the regression of a metastatic cancer at a distance from the irradiated site.
