Blue Book: Radiotherapy

Question 1

What is radiotherapy?

Answer 1

Therapeutic use of ionising radiation to damage cancerous cells.

Question 2

How can radiotherapy be used in the management of cancer?

Answer 2

1) Sole treatment (radical/curatice/definitive) eg prostate cancer.
2) Neo-adjuvant (before curative surgery) to reduce risk of recurrence. Eg rectal cancer.
3) Adjuvantly (following curative chemo) to reduce the risk of local recurrence eg breast cancer.
4) Palliation of symptoms or control cancer growth.

Question 3

Name 3 types of radioation therapy.

Answer 3

External beam radiation.
Brachytherapy
Unsealed source or radioisotope therapy.

Question 4

What is name of the machines that deliver radiotherapy and what are the units of radiation?

The overall required dose are split into what?

Answer 4

A linear accelerator 
Gray unit (Gy)

Fractions

Question 5

How do the X-rays/photons cause damage and what to they spare?

Answer 5

X-rays penetrate deep into the tissue where secondary electrons cause damage to DNA of cancer and normal cells. Sparing the overlying skin. Normal cell repair themselves whilst cancer cells cannot.

Question 6

What 3 factors affect the toxicity of radiotherapy?

Answer 6

1. Treatment issues: dose, volume treated, dose per fractions, treatment time.
2. Co-moridites, smoking
3. Intrinsic radio-sensitivity of the cancer cells (seminoma and hodgkins are highly radiosensitive), tumour hypoxia, tumour re-population and additional treatment.

Question 7

What is the therapeutic index?

Answer 7

Balance between tumour control and side effects of radiotherapy.

Question 8

What is the purpose of concurrent chemotherapy?

What are advantages/disadvantages.

Answer 8

Chemotherapy given during radiotherapy which is thought to act as a radiosensitiser. Improving efficacy of the radiotherapy treatment without having to increase the dose.

But increased side effects of both radio and chemotherpy.

Question 9

What happens at each stage of pre treatment?

What happens at planning treatment?

Answer 9

Pre-treatment

• Diagnosis and imaging
• MDT
• consent
• patient immobilisatoin
• Planning CT

Planning

• disease delineation by clinical oncologist
• additional margins added
• complex treatment plans developed by medical physics team in collaboration with physicians

Question 10

Treatment and follow up

Answer 10

• Patient attends daily treatments
• Treatment delivered by radiographers.
• Clinical review during treatment
• Long term follow up

Question 11

The most common external beam radiotherapy in the UK is 3D-conformal radiotherapy.

What is it? How is it planned?

Answer 11

Radiotherapy based upon the 3D shape of their tumour.

Info gained from CT scan, the tumour is delineated on each CT slide (Gross tumour volume GTV) and a margin is added to for microscopic disease (clinical target volume CTV) and another margiun is added for minor variations in patient and tumour position (planning target volume PTV). A radiotherapy plan is made to this shae, to treat tumour but avoid as much normal tissue.

The patient must be in a consistent position for CT and delivery of radiotherapy= immobilisation.

Question 12

Describe acute side effects of radiotherapy?

Answer 12

during treatment ususally after 5-10 fractions and increase during treatment. Caused by damage to normal tissue but are reversible: eg localized skin reaction, oral mucositis, dirrhoea.

Question 13

Describe late side effects of radiotherpay.

Answer 13

After 3 months-1 year. Often irreversible and may worsen with time. Damage to normal cells cannot be repaired and partly due to fibrosis and blood vessel damage within the irradiated tissue.
Eg: lung fibrosis, skin atrophy, infertility.

Radiotherapy is carcinogenic increased risk of second malignancy decades after treatment. Risk is greater in young patients.

Teratogenic. Avoid in pregnancy.

Question 14

What is brachytherapy?

What cancers is it commonly used for?

Answer 14

Radiation source is placed within or close to the tumour= delivery of localised high radiation dose to a small tumour volume= increased tumour control but minimise damage to surrounding tissue.

Prostate, gynaecological, oesophageal, head and neck.

Question 15

What are the two main types of brachytherapy?

Before discharging a patient what is it important to tell them?

Answer 15

Intracavity: radioactive material is placed in cavity (uterus and cervix)

Interstitial (put into target)

Radiation protection is important, and risk to others.

Question 16

Radioisotopes can be used to treat some cancers. Can you think of an example?

Answer 16

Radioactive iodine I-131 for common for of thyroid cancer. Thyroid takes up iodine and emits radiation causing radioactive decay.

Can’t go near anyone for 4 days.