Treatment: Radiotherapy Flashcards
What is radiotherapy?
The use of ionising radiation in the management of oncological patients. Ionising radiation produces free radicals which damage the cancer cells’ DNA,
which unlike normal cells, are unable to repair themselves prior to the delivery of the
next radiotherapy dose (fraction).
What is meant by ‘ionising’ radiation?
Ionising = refers to type of radiation in which
absorption of energy results in ejection of one
or more orbital electrons from an atom or molecule; e.g., X rays and gamma rays
How does radiotherapy work? (DNA level)
• Cause DNA strand breaks by damaging base pairs • DNA strand breaks can lead to a number of outcomes: – Repair – Cell death (apoptosis) – Retarded cell growth – Impaired cell division
How is the radiation quantified?
- Radiation is quantified in terms of the amount of absorbed dose.
- Units are expressed in Gray (Gy), where
- 1 Gy = 1 Joule of energy absorbed/kg of absorbing material
Outline radiotherapy intent (radical/adjuvant/palliative).
- Radical Curative
- Adjuvant Improving outcomes
- Palliative Symptom control
What are the two main types of radiotherapy?
- External beam
- Brachytherapy
Describe briefly external beam radiotherapy.
Uses a photon/proton/electron therapy beam directed at the cancer.
Describe briefly brachytherapy.
Internal placement of radioactive source into the tumour e.g. prostate cancer.
Briefly outline the radiotherapy planning pathway.
- Pre-planning investigations = PET CT/CT/MRI + treatment intent
- CT planning = patient set up and immobilisation / CT planning scan (3D or 4D)
- Treatment planning = plan for treatment using planning scan. Beam arrangements/dosage/plan evaluation
- Treatment = Verify plan and patient positioning. Treatment delivery/treatment review.
- Follow-up = post-treatment review. Ongoing for years.
What is SABR and briefly describe how it works.
- Stereotactic abalative radiotherapy
• SABR – very high precision high dose radiotherapy
• Delivers biologically equivalent dose of ~180 Gy
• Typical dose fractionations –54 Gy in 3 fractions
• Very high local control rates (80-90%)
• Used routinely for early stage lung cancer
• Being investigated in other cancer sites and for
metastatic disease
Outline the early/short-term side-effects of radiotherapy (short term inflammatory effect).
NOTE: most likely MCQs are on side-effects
*Note: think locally - where is beam directed; gives idea of structures effect and therefore the side-effects.
• Tiredness • Skin reaction (radiation dermatitis) • Hair loss • Nausea • Hoarseness • Discomfort/Pain • Mucositis – Symptomss relate to area affected: e.g. Oral, Oesophageal, Bowel, Bladder – Difficulty swallowing – Loss of appetite/weight loss – Altered bowel habits/urinary discomfort
What is dry desquamation?
- Skin reaction due to radiotherapy cycle
- This is where new cells proliferate before dead cells can slough or shed
- The skin is closed and is less likely to become infected than in moist desquamation
What is moist desquamation?
- Skin reaction due to radiotherapy cycle.
- This is where the epithelial layer is broken/compromised
- New cells have not replaced the dead cells which have sloughed
- The skin is now exposed to infection
Outline acute mucositis and the resultant symptoms based on area of body effected.
- Develops ~2 weeks after radiotherapy commences
- Continue 5-6 weeks post-treatment
- Oesophagus: dysphagia/odynophagia/weight loss
- Bowel: diarrhoea
- Bladder: urinary frequency/haematuria
List the late term side-effects of radiotherapy aka the fibrotic/scarring effect.
*Note: again, it is easier to think about what part of the body is being treated. If asked in an OSCE just localise the anatomy and suggest side-effects related to scarring of these areas.
- Tiredness
- Skin (thinner)
- Fibrosis (soft tissue less supple)
- Pain
- Hair loss (thinner, sometimes permanent)
- Dry mouth (xerostomia)/dry cough (pneumonitis/fibrosis)
- Necrosis (when healing doesn’t take place post-xrt)
- Altered bowel habits/urinary discomfort (cystitis)
- Infertility
- Cardiac Toxicity
- Secondary Cancers (eg sarcomas)
