Radiotherapy

Question 1

What are cancer therapy options?

Answer 1

Local - Surgery or radiotherapy
Systemic - Chemotherapy
Can be Curative or Palliative

Question 2

Give examples of acute effects of radiotherapy

Answer 2

Moist desquamation
Erythema
Oedema

Question 3

Give examples of late effects of radiotherapy

Answer 3

Fibrosis
Telangectasia
Atrophy
Retraction

Question 4

Why is radiotherapy fractionated?

Answer 4

Tumour gets same amount of radiation
Surrounding tissues get less
Surrounding tissues have time to recover between fractions
Tumour cells are more rapidly dividing and have worse DNA damage repair pathways so recover worse

Question 5

What’s the scoring system for radiotherapy adverse effects?

Answer 5

CTCAE
Grade 1: asymptomatic or mild. No intervention required.
Grade 2: Minimal, local or non-invasive intervention
Grade 3: Medically significant but not life threatening. Hospitalisation indicated.
Grade 4: Life threatening.
Grade 5: death.

Question 6

How does radiotherapy work?

Answer 6

Directly ionises DNA

Indirectly ionises water to create O2 radicals, which ionise DNA

Question 7

What does ionisation of DNA cause?

Answer 7

Single strand breaks
Double strand breaks
Crosslinking of strands

Question 8

Which tissues are most and least sensitive to radiation?

Answer 8

Most; WBCs, intestinal epithelium, reproductive cells
Quite; vascular endothelium, mucous membranes
Medium; Glial cells, lung
Least; skeletal muscle, bone, neurones

Question 9

How do patients respond to radiation?

Answer 9

Minutes; production of TGF beta
Hours; Apoptosis, H2AX production
Days; Inflammatory cell response
Weeks; anti-fibrotic cytokines
Months; ECM and collagen deposition
Years; Collagen synthesis and degradation, potential tissue damage so hypoxia

Question 10

What influences a patient’s response to radiation?

Answer 10

30% is therapeutic factors eg fractionation

Genetics makes up a percentage too

Question 11

What are some known predictors of radiotherapy response?

Answer 11

Radiation dose
Electron boost
Acute response associated with late effects
Breast size (bigger is worse)
Family radiosensitive

Question 12

What is the heredity of radiosensitivity?

Answer 12

First degree relatives who are radiosensitive are predictors of radiosensitivity
Twin studies using lymphocytes showed radiation-induced apoptosis

Question 13

What are some syndromes associated with radiosensitivity

Answer 13

Ataxia telangectasia
Nijmegen breakage syndrome
ICF syndrome
RIDDLE syndrome
Bloom syndrome