Radiotherapy Flashcards
Who administers radiotherapy
Radiographers
Clinical oncologists
What type of ionising radiation is used in radiotherapy
Electrons
Photons - Xrays
Proton beams
Types of radiotherapy machine
Linear particle accelerators - electrons and photons
Cyclotrons - proton beam therapy
Action of radiotherapy
Direct - DNA damage causing cell death
Indirect - Radiation ionises water molecules which produces free radicals that damage DNA causing cell death
Types of radiotherapy
External beam (most common)
Brachytherapy
Radioactive substance injected e.g. iodine radioisotope
Brachytherapy features
Used as a boost treatment or primary treatment
Radiotherapy delivered locally so less side effects
Which cancers are brachytherapy used in
Prostate and cervical
Which cancer used radioactive substance injections
Thyroid cancer
Aim of radiotherapy
Deliver the highest dose possible to the tumour whilst minimising the dose to normal tissue
Mechanism of external beam radiotherapy
Several beams of radiation converge on tumour target
Intensity and shape of the beam can be modulated by multileaf collimators
Patient journey for radiotherapy
- CT or MRI scan for planning
- Simulator
- Pre-treatment calculations made
- Linear accelerator
- Onboard imaging
How long does the radiotherapy process take
Up to 28 days from referral to treatment
What are radiosensitisers
Low dose chemotherapy to make tumour cells more prone to damage
Purpose of neoadjuvant radiotherapy
Shrink tumour size before surgery to facilitate clear surgical margins
Benefits of neoadjuvant radiotherapy
Reduction in post-op regional recurrence
Reduction in distal metastasise
Improve long term survival
Chemoradiation
Neoadjuvant or adjuvant radiation often given with chemotherapy to increase benefits but side effect profile is more severe
When is adjuvant chemotherapy given?
When risk of regional cancer recurrence is higher due to :
- positive or close surgical margins
- lymph node involvement
- high grade tumour
Which cancers can be cured by chemoradiation?
Head and neck
Cervical
Bladder
Anal
Prostate cancer - radiotherapy and hormone therapy
Fractions
Balance tumour cell death with normal cell death therefore given in sessions
Indications for palliative radiotherapy
Tumour related bleeding
Tumour related pain
Pressure symptoms due to tumour - spinal cord compression/ SVCO
Risks of radiotherapy
Works in 60% of cases
May take 4 - 6 weeks
May worsen tumour-related symptoms - temporary oedema due to inflammation
Early side effects of radiotherapy
Fatigue Hair loss Nausea and vomiting Dysphagia Oral mucositis Radiation cystitis Diarrhoea Low blood counts
Late side effects
Pneumonitis - breathlessness
Lung fibrosis
Heart cardiomyopathy and pericardiofibrosis
Bowel strictures and adhesions/ fistulas
Dermatitis - erythema
Lymphoedema
Sterility
Bone fractures
Cataracts/ loss of sight
Mouth ulcers/ dry mouth
