Radiation Oncology

Question 1

Describe the principles of radiation oncology

Answer 1

Radiation excites the cells causing the formation of free radicals -> free radicals self-propagate forming more free radicals -> free radicals cause DNA damage -> lead to cell damage and tissue death

Question 2

List the 5R’s of Radiotherapy

Answer 2

Redistribution: by providing sequential doses the cells that were not in optimal state are now more available
Repair: malignant cells have worse repair mechanisms than normal cells, so do not adequately repair before next dose
Reoxygenate: Malignant cells can be radioresistant if hypoxic, by providing multiple doses it increases oxygenation to the area
Repopulate: malignant cells have worse time reforming population
Radiosensitive: some tumour types are more sensitive to radiotherapy

Question 3

What phase of the cell cycle is radiotherapy most effective

Answer 3

M and S phase

Question 4

Describe the therapeutic ratio as it applies to radiotherapy

Answer 4

It is the relationship between the effectiveness and the side effects. Radiotherapy is most effective when there is a strong effect with minimal side effects

Question 5

What are some advantages of radiotherapy over other types of cancer therapy?

Answer 5

Better cosmesis
Minimally invasive
Less systemic effects allow the preservation of other tissues
Is a local regional therapy

Question 6

What are the acute and chronic side effects of radiotherapy

Answer 6

Acute:
- Decreased blood flow
- Endothelial tissue edema
- Tissue necrosis
Chronic:
- Thickened blood vessels
- Chronic ischemia
- Tissue atrophy
- Tissue fibrosis

Question 7

List the two types of radiotherapy.

Answer 7

Curative: 4000-8000 cGy
Palliative: 600-3000 cGy