Radiotherapy

Question 1

What are the 4 aims that RT is delivered for?

Answer 1

RADICAL = ie curing cancer, often given in combination with chemo
ADJUVANT = in addition to curative surgery to reduce the risk of local recurrence
PALLIATIVE = to help symptom control, especially of mets
NEO-ADJUVANT = prior to surgery eg rectal cancer

Question 2

What are the two main ways RT is used?

Answer 2

NB always uses ionising radiation
1. PHOTON - penetrate deep into tissue and spare over-lying skin
2. ELECTRON - damage DNA directly and deliver their dose superficially just below the skin surface

Question 3

What further RT methods are there?

Answer 3

-Brachytherapy (internal, allows localised radiation to be delivered to a small tumour, used in prostate, gynaecologist, oesophageal and H+N)
-Radioisotopes (eg radioactive iodine for thyroid cancer)
-Stereotactic RT (well-defined small tumours eg brain mets, allows a small number of large dose RT)
-Intensity modulated RT / arc therapy (allows continuous treatment delivery as the beam moves around the patient)

Question 4

How is RT dose measured?

Answer 4

-Absorbed dose is expressed as Gray (Gy)

Question 5

How is RT delivered?

Answer 5

-Commonly delivered as a series of small doses called fractions rather than a single dose
-No. of fractions and dose is dependent on the treatment aim (ie radical vs palliative)

Question 6

How is RT beam designed for specific tumours?

Answer 6

3 measurements taken into account:
1. GTV (Gross Tumour Volume) = tumour visible on scan
2. CTV (Clinical Target Volume) = includes microscopic spread, not visible on scan
3. PTV (Planning Target Volume) = includes possible tumour movement or variability on treatment day

Question 7

What side effects can be expected from head and neck RT?

Answer 7

-Radiation dermatitis - painful skin reaction, can become more severe throughout treatment
-Mucositis - painful
-Thick oral secretions
-Loss of taste
-Fatigue - can be severe
-Dry mouth

Question 8

What side effects can be expected from prostate RT?

Answer 8

-Cystitis-like symptoms (dysuria, frequency, urgency)
-Diarrhoea
-Rectal bleeding
-Poor urine flow (prostatitis - treat with tamsulosin alpha blocker)
-Haematuria
-Abdo pain
-Nausea

Question 9

What side effects can be expected from lung RT?

Answer 9

-Odynophagia / oesophagitis
-Cough
-Chest pain
-Nausea (more common in high-up tumours)
-Pneumonitis (usually 6-8 weeks post RT)

Question 10

What are the main types of general side effects you could expect from RT?

Answer 10

ACUTE - develops within treatment and peaks a few weeks post-treatment, includes skin reactions, oral mucositis, diarrhoea, ie INFLAMMATION
LATE - develops >3 months post-treatment eg lung fibrosis, skin atrophy, infertility