Radiotherapy Flashcards
In what cancers can radiotherapy be used as the sole treatment?
Prostate
When can radiotherapy be used as a neoadjuvant treatment?
Rectal cancer
When can radiotherapy be used as an adjuvant treatment?
Breast cancer
How can radiotherapy be delivered?
Photons/X-rays: External beam RT (most common)
Electrons
Radio-isotopes
Protons
What is the science behind radiotherapy?
X-rays at one end of electromagnetic spectrum
Very high energy, very short wavelength
Delivered by LINAC machine penetrating deep into tissue sparing overlying skin
Produce secondary electrons & free radicals causing DNA damage
What is radiation dose measured in? What is the number of treatments referred to as?
Gray
Fractions
What is the therapeutic index?
Balance between tumour control and the SE of radiotherapy
What is the gross tumour volume & clinical target volume& the planning target volume?
GTV: Main bulk of the tumour
CTV: Margin added for microscopic disease spread
PTV: Margin added to allow minor daily variations in patient & tumour position
What are the acute SE of radiotherapy?
Develop during treatment Usually after first 5-10fractions Often peak few weeks after treatment Due to damage of normal tissue & ability of normal cells to repair damage Localised skin reaction Oral mucositis Diarrhoea
What are the late SE of radiotherapy?
Develop at least 3months-years after treatment
Often irreversible
Develop due to damage to normal cells, partly due to fibrosis & blood vessel damage in irradiated tissue
Lung fibrosis
Skin atrophy
Infertility
What is brachytherapy?
Form of radiation treatment where radiation sources are placed within/close to the tumour allowing delivery of localised high radiation dose to a small tumour volume inc chance of control
What cancers can be treated with brachytherapy?
Prostate
Gynae
Oesophageal
Head & neck
What are the 2 types of brachytherapy?
Intracavity: Radioactive material placed inside a body cavity (uterus, cervix)
Interstitial: Material put into the target (prostate)
What is the most commonly used radio isotope?
Iodine I-131
Thyroid cancers
Iodine taken up and concentrated in any remaining thyroid tissue normal or malignant ablating thyroid cells
How does RT delivered by photons work?
Causes DNA damage to both cancer and normal cells
Targets deep tissues but spares overlying skin
Produces secondary electron in tissues
How does RT delivered by electrons work?
Directly damages DNA
Deliver dose superficially (just below skin surface)
Normal cells can repair themselves and survive
What are the specific side effects of RT for prostate cancer?
Proctitis (rectum)
Cystitis (bladder)
Long-term: Telangiectasia of bladder/rectum
Incompetent bladder & inc urination
What are the specific side effects of RT for breast cancer?
Acute: Fatigue, skin problems (dry/moist desquamation), pain around scar, skin thickening w/oedema/lymphoedema
Chronic: Shrinking of the breast w/fibrosis, pulmonary fibrosis
What is the scoring system for RT side effects for breast cancer?
RTOG 0: No visible changes
RTOG 1: Faint/dull erythema (frequent moisture)
RTOG 2a: bright erythema/dry desquamation, sore, itchy, tight
RTOG 2b: Patchy, moist desquamation, moist erythema
RTOG 3: Confluent moist desquamation, yellow/green exudate
RTOG 4: Ulceration, bleeding, necrosis
What is the preparation required for RT for prostate cancer?
Full bladder: Moves S.bowel up & out of radiation field, L.bowel move out of field so smaller radiation dose
Empty rectum: micro-enema
What are the side effects associated with RT to the head and neck?
Skin changes Jaw stiffness Tooth decay Fatigue Soreness of mouth/throat Xerostomia voice and taste changes changes in hearing changes in skin texture
