Radiotherapy

Question 1

What is radical treatment?

Answer 1

Intent to cure

Question 2

What is adjuvant treatment?

Answer 2

After surgery

Question 3

What is palliative treatment?

Answer 3

Used to control symptoms

Question 4

What is external beam radiotherapy?

Answer 4

Delivered using a linear accelerator

Question 5

What is brachytherapy?

Answer 5

Radioactive implants (iridium wire, gold seeds)

Question 6

What are radioisotopes?

Answer 6

• Radioiodine for thyroid cancer

- Strontium/radium for prostate cancer

Question 7

What is radiotherapy?

Answer 7

The use of ionising photons (x-rays), electrons or other charged particles to treat disease, usually cancer

• Ionising radiation produces reactive oxygen species within cells, which can damage DNA
• Radiation can also directly damage DNA

Question 8

How does radiotherapy work?

Answer 8

Radiotherapy damages DNA
- DNA damage maybe repairable but if extensive will cause cell death or death of daughter cells

Radiation damages all cells
- Dividing cells (e.g. cancer) do not repair as effectively as non-cancer cells

Question 9

What normal tissues are highly radiosensitive?

Answer 9

Marrow
Gonad
Gut mucosa
Lymphatic tissue
Eye lens

Question 10

What malignant tissues are highly radiosensitive?

Answer 10

Lymphoma
Leukaemia
Seminoma
Ewing's sarcoma
Many embryonal tumours

Question 11

What normal tissues are moderately radiosensitive?

Answer 11

Liver
Kidney
Lung
Skin
Breast
Gut wall
Nervous tissue

Question 12

What malignant tissues are moderately radiosensitive?

Answer 12

Small-cell lung cancer
Breast cancer
Squamous carcinomas
Adenocarcinomas of bowel
Glioma

Question 13

What normal tissues are relatively insensitive to radiotherapy?

Answer 13

Bone
Connective tissue
Muscle

Question 14

What malignant tissues are relatively insensitive to radiotherapy?

Answer 14

Sarcoma of bone and connective tissues

Melanoma

Question 15

What is therapeutic radiation measured in?

Answer 15

Gray (Gy)

1 Gray = 1 Joule/kg

Question 16

How can the therapeutic gain be improved and side effects reduced?

Answer 16

• Choose right type of radiation
• Divide treatment into smaller fractions
• Planning, effective and accurate targeting of the tumour

Question 17

What types of radiation are there?

Answer 17

• Low energy (kilovoltage, kV)
• High energy (megavoltage mV)
• The energy and type of radiation determines the depth of penetration of the radiation

Question 18

What is fractionation?

Answer 18

• The size of doses given
• Allow 6 hours between to allow normal tissues to repair DNA damage
• Smaller fractionation = fewer long term side effects
• Larger fractionation = more convenient but more side effects

Question 19

What are acute radiotherapy side effects?

Answer 19

• Fatigue: common, mild
• Sore skin: if severe can desquamate
• Mucositis: dysphagia
• Cough: RT to lung, breast, oesophagus
• Hair loss: often permanent
• Nausea: RT to gut, brain
• Anaemia: RT to spine, pelvis

Question 20

What are the late radiotherapy side effects?

Answer 20

• Tissue fibrosis
• Lymphoedema
• Telangiectasia
• Radionecrosis
• Osteoradionecrosis
• Hypo-thyroid, pit, gonad: infertility
• Neurological damage
• Second malignancy
• Arrested bone growth

Question 21

What must occur before therapy starts?

Answer 21

Patient must be planned/simulated for optimum accuracy