Radiotherapy Flashcards
how is radiotherapy more commonly given
in multi-modality treatment
what is radiotherapy
the use of ionising radiation to treat cancer
what type of cancers are treated with radiotherapy
most solid malignancies and some liquid
how many cancer patients get R/T
50-60%
how many patients are cured by R/T
40%
what types of ionising radiation afterused
X-rays, gamma rays, beta particles, alpha particles, neutrons and protons
what radiation is used in conventional external beam R/T
X rays
how was radiation originally deliviered
one big dose, had lots of severe side effects
what is fractionated radiotherapy
many smaller doses of radiation for many weeks (up to 7 for more resistant cancers like head and neck)
what equipment delivers R/T
linear accelerators (LINACS)
what happens in the treatment planning
immobilisation, MRI and CT, image fusion, volume delineation, Treatment planning, plan verification, pre-treatment imaging, treatment (30secs)
what is image fusion good for
finding tumour and any other damaged tissue
what is the conventional fraction for breast cancer treatment
50Gy (2 Gy x 25) +/- lumpectomy cavity boost
what is the hypofractionation for breast cancer treatment
42.5 Gy (2.66 Gy x 16 fractions), 40Gy (2.66 x 15 fractions)
what is accelerated radiotherapy
schedule in which the rate of dose -accumulation exceeds 10Gy/week
what is Hyperfractionation
ant schedule employing a dose per fraction of less than 1.8Gy
why is radiotherapy given (5)
- curative intent
- shrink cancer before surgery
- to reduce risk of recurrence post surgery
- to complement chemo
- to control symptoms and increase QoL (palliative)
what does neoadjuvant mean
given before surgery
what does adjuvant mean
given after surgery
Brachytherapy
rods inserted into the tumour
what is brachytherapy commonly used for
prostate cancer and uterine and cervical cancer
Brachytherapy for prostate cancer
plastic catheters inserted through the perineum and into the prostate under anaesthesia
Brachytherapy: what is the dwell time
when the radioactive rods are in the tumour
advantage of brachytherapy
treatment is done in 2-5 days not 6 weeks
disadvantages of brachytherapy
strict bed rest while catheters are inside so movement is restricted
how do LINACS work - EBRT
uses microwaves to accelerate electrons that collide with a heavy metal target to produce X-rays which are focused down onto the patient
what is the therapeutic ratio in EBRT (external beam radiotherapy)
maximising the therapeutic effect and minimising toxic effect on normal tissue
How does Intensity-modulated radiation therapy (IMRT) work
uses computer-controlled LINACS to deliver precise radiation doses to the tumour, or specific areas within the tumour
what does IMRT allow for
higher radiation doses to be focused to regions in the tumour while minimising the dose to surrounding structures
what is IMRT currently being used to treat mostly
prostate, head and neck and CNS cancers
How does radiation therapy kill cancer cells
stops them dividing and growing
early (acute) side effects of radiation treatment
tiredness and skin problems such as sensitivity, redness and swelling
less common acute side effects of radiation therapy
hair loss in area, eating issues, nausea and vomiting, soreness and swelling, mouth issues, diarrhoea, headaches, urinary/bladder changes
late (chronic and progressive) side effects of radiation therapy
brain, kidney, colon, spinal cord, mouth, rectal, lung and joint changes, secondary cancers, lymphedema, infertility
what does alpha radiation consist of
2 neutrons and 2 protons bound together so tightly that it acts like a fundamental particle
what does beta radiation consist of
high speed e- that originate in the nucleus. electrons of low energy should be referred to as delta rays
what does gamma radiation consist of
its an electromagnetic radiation that consists of photons. They consist of quanta (packets) of energy that are transferred in wave motion
difference in X-rays and gamma rays
their origin - gamma rays result from nuclear changes and X-rays are emitted when atomic e- undergo a change in orbit
which cells are more resistant to radiation
hypoxic cells
methods of selectively attacking hypoxic cells
- Hyperbaric oxygen (HBO)
- high-LET radiation, hypoxic cells sensitisers
- increase Hb levels
what causes 1 M-phase cell to become 2 G1 cells
non-uniform distribution
in which phase of the cell cycle are cells particularly resistant to radiation
S phase
when is cancer less effective at repairing DNA damage
at small doses of RT
what are the 4 R’s of radiotherapy?
Reoxygenation
Redistribution
Repair
Repopulation
which cancers are highly sensitive to radiotherapy
lymphoma, leukaemia, seminoma, dysgerminoma
which cancers are fairly highly sensitive to radiotherapy
squamous cell cancers of the glottis, oropharyngeal, bladder and cervical epithelia
which cancers not very sensitive to radiotherapy
breast, salivary gland, hepatomas, renal, pancreatic
which cancers have low sensitivity to radiotherapy
rhabdomyosarcoma
what regimens are currently recommended for RT for breast cancer
50Gy in 25 daily fractions over 5 weeks or 40Gy in 15 daily fractions over 3 weeks
