Radiotherapy Flashcards
What is radiotherapy?
A highly regulated delivery of ionising radiation
How does radiotherapy treat cancer?
It damages the DNA of the cancer cells (can also affect normal cells producing side effects in the treatment area)
Direct DNA damage or indirect - radiation causes free radical production, which causes DNA damage and cell death
What different types of ionising radiation are used in the treatment of cancer?
Electrons
Photons (x rays)
Proton beams
What types of radiotherapy are there?
External beam - most common
Brachytherapy - either as a boost or primary treatment, a sealed radiation source placed inside or next to area requiring treatment
Systemic treatment - radioactive substances injected/swallowed e.g iodine 131 radioisotope used for thyroid cancer
Brachytherapy is used in what cancer types?
Prostate
Cervical
What is the aim of RT?
Deliver highest dose possible to tumour
Minimise dose to surrounding ‘normal tissue’
What are radiosensitisers?
Agents that make radiotherapy more effective when given during/ shortly prior to radiation delivery
E.g cisplatin, temozolamide
What is radical radiotherapy?
When radiotherapy used to treat cancer as part of a curative strategy.
May be used in different settings:
Neoadjuvant- before
Adjuvant - after
Definitive
What is the role of neoadjuvant radical radiotherapy?
Tumour downsizing, facilitating clear surgical resection margins
Reduce post op regional recurrence rate
Theoretically reduce rate of distant metastasis
What can neoadjuvant radiotherapy be given with?
Simultaneous chemotherapy to increase efficacy
= chemoradiation
Side effect profile more severe, so patients need to be suitably fit
Give some examples where chemoradiotherapy is used
Oesophageal cancer
Rectal cancer
When is adjuvant radiotherapy given?
In situations where risk of locoregional cancer recurrence after definitive surgery is considerable due to:
Positive or close surgical margins
Involved lymph nodes
High grade tumour
Give examples of when adjuvant radiotherapy is used
Breast cancer
Endometrial cancer
Cervical cancer
Head and neck cancers
What can adjuvant radiotherapy be combined with?
Chemotherapy
In breast cancer after WLE, adjuvant radiotherapy has been show to reduce locoregional recurrence by…
50%
The combination of WLE and adjuvant radiotherapy has equal efficacy to…
A mastectomy with respect to long term local control rates
There are some cancers that can be cured by chemoradiation alone, without need for surgical input, for example…
Head and neck Cervical Bladder Anal Prostate - can be cured with radical RT in addition to hormone treatment (LHRH agonists)
What is palliative radiotherapy given for?
Symptom control
Usually in 1,5,10 fractions as opposed to radical RT given between 20-37 fractions
What are some examples of indications for palliative RT?
Tumour related bleeding, pain or other pressure related sequelae - MSCC, SVCO
Why after palliative RT might symptoms temporarily worsen?
Due to the oedema caused from the tissue destruction
How long can it take for symptom relief to occur after palliative RT?
Can take 4-6 weeks
What is radiotherapy dermatitis?
Side effect of external beam ionising radiation.
Confined to area of skin irradiated, skin changes are sharply demarcated
Can be acute or chronic
On examination:
Erythema
Desquamation (peeling)
If severe: necrosis and ulceration
What are some short term side effects?
Depends on area treated Erythema Lymphoedema Nausea and vomiting (more likely if treatment near stomach or brain) Hair loss (only in treated area) Dysphagia, sore throat, mucositis Low blood counts if bone marrow affected Diarrhoea Dysuria Sterility
What late side effects can occur?
Skin - pigmentation, telangiectasia Bone - fractures, impaired growth Eyes - cataracts Lungs - fibrosis Heart - cardiomyopathy Bowel - strictures, adhesions, fistulas Gonads - infertility, early menopause
