Week 12 - Radiotherapy Flashcards
What gives an atom stability?
The protons = electrons
What is ionising radiation?
Radiation consisting of particles, X-rays or gamma rays with sufficient energy to cause ionisation in the medium through which it passes
What is ionisation?
The process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions, often in conjugation with other chemical changes
Which atoms emit radioactive decay?
Atoms of natural radioactive substances with unstable nuclei
Name some ionising radiation
- electromagnetic waves (X-rays or gamma rays)
- alpha or á particles (short range - more damaging)
- beta or b particles
Many radioactive substances emit all three
What is radiotherapy?
The treatment of disease by ionising radiation
What is an advantage of radiation?
Targeted to damage cancer cells - healthy cells can recover
How does ionising radiation have an effect on tissues/cells?
- can penetrate tissues and alter the nuclear material (I.e. DNA)
- disrupting cell growth and reproduction
What effect does radiation have on human cells when it damages them and how?
-damages cells - causes apoptosis
- when a high energy ray hits a molecule, it can cause it to break up
- this can form free radicals which can cause further damage to the inside of the cell
- leads to apoptosis
Which radiations are more likely to cause tissue or cell damage and why?
- alpha and gamma radiation
- more likely to cause tissue or cell damage because they are more effective at producing ionisation
Which are the preferred radiations to treat malignancies and why?
Alpha and gamma
-more likely to cause tissue or cell damage because are more effective at producing ionisation
When may radiotherapy be used?
- treat cancer as a stand alone treatment
- shrink tumour before surgery
- reduce cancer returning after surgery
- control symptoms or reduce pain if cancer is no longer treatable
- reduce growth of cells - Graves’ disease
- palliative radiotherapy
Give examples of the malignancies specifically confined to one area that radiotherapy aims to treat
Brain Skin Prostate Breast Uterus
What are the types of radio therapy?
Internal and external
What is external radiotherapy?
- supplied from outside the body
- local exposure-targeting specific cells
What is internal radiotherapy?
- utilising radioactive implants placed inside the body
- local exposure-targeting specific cells
What is each exposure of radiotherapy classed as?
A fraction
How is external radiotherapy given?
- usually given over several days or weeks
- mon-fri with weekend off
- mark target area - need to lie in certain position
- motionless
- 5 mins per fraction
- painless procedure
How does a radiotherapy machine work?
A metal element is heated to produce electrons. These accelerate in an electric field towards a piece of tungsten metal, which then emits high-energy X-rays when they hit it
What is conformal radiotherapy? (CRT)
Use of metal blocks to direct the beam of ionising radiation
-3D CRT
What is an advantage of conformal radiotherapy (CRT)?
-more closely targets the shape of the tumour
What is conformal radiotherapy (CRT) routinely used for?
Prostate cancer
What is internal radiotherapy also known as?
Brachytherapy
How is internal radiotherapy given?
-may be given once or only a few times
-usually involves short stay in hospital
-radioactive wires (a few days)
or
- radioactive seeds (radioactive gold or iodine a permanent - small amounts of ionising radiation placed in tumour - degrade over time) put in to affected area
-IV or in liquid form
-may have to limit contact with people
What may be limited when having internal radiotherapy treatment?
Contact with people
What is radioactivity measured with?
A Geiger counter
What radiation is most likely to be used for radioactive pellets and why?
Alpha radiation
-shorter range and more powerful
What is given when treating someone wit. internal radiotherapy using IV or liquid form?
- strontium 89
- samarium 153 (some bone cancers)
- iodine 131 (thyroid gland)
- radium 223 (secondary bone cancer- trials)
-may also be used to relieve blockages of the oesophagus
What do the side effects of radiotherapy depend on?
- dependant on area being treated
- dose of radiation
- physical well being at the time of treatment
When can side effects appear?
- during treatment
- weeks/months after treatment
Why are side effects caused by radiotherapy?
- most people experience some side effects
- caused by damage to healthy cells - may take time to recover
What are the side effects of radiotherapy?
- tiredness
- N&V
- sore skin
- muscle and joint pain
- fertility
Why can radiotherapy cause tiredness as a side effect?
- physical exertion of going for treatment everyday
- anaemia - destruction of erythrocytes
- less o2 carrying capacity
-extreme cases - transfusion
- bone marrow affected - pelvis, abdo, prostate
- diarrhoea
Why can radiotherapy cause N&V as a side effect?
- GI tract, brain (depends on area of body receiving treatment)
- loss of appetite
What can be done to control N&V as a side effect of radiotherapy?
- alter diet
- prescribe anti-emetics (e.g. domperidone)
- dexamethasone, 5HT antagonists, anti-histamines
Why might sore skin be caused as a side effect of radiation?
- local reaction to the radiation
- sore and red - avoid irritants
-temporary hair loss in area
Why might muscle and joint pain be caused as a side effect of radiation in radiotherapy?
- treatment may cause muscle stiffness in affected area
- swelling of joints
-light exercise/physiotherapy
Why may fertility be affected as a side effect of radiotherapy?
- loss of libido (tiredness)
- pelvic area - may effect ovarian function in women - induce an early menopause causing infertility
- prostate - impotence/infertility
What are the risks of radiotherapy?
-increased dose - increases slight risk to normal cells and could cause cancer
Why might the thyroid gland need radiotherapy?
- Graves’ disease (swelling of the neck and protrusion of the eyes resulting from an overactive thyroid gland)
- reduce activity of thyroid gland by destroying cells
- less T3/T4 release
What 2 treatments appear to be the future of radiotherapy?
Hyperfractioned radiotherapy
Hypofractioned radiotherapy
What is hyperfractioned radiotherapy?
- increasing frequency of fractions - more than one a day
- e.g. Continuous hyperfractioned accelerated radiotherapy
- treatment given over 12 days rather than 4/6 weeks
- total dose the same
- requires hospital stay
- only available in a few centres
What is Hypofractioned radiotherapy?
- increase dose of radiotherapy per fraction - lower the frequency of fractions
- overall = reduction in the total amount of radiotherapy received
- need to assess reduction in side effects and reduction in risk of recurrence of the cancer
What is stereotactic radiotherapy?
- novel treatment used to treat small round tumours usually found in the head
- treatment delivered from many different points in the head
- external frame used to keep head in place
What may be treated by stereotactic radiotherapy?
- used to treat a number of benign conditions
- pituitary adenomas
- acoustic neuromas
- growths at the base of the skull (meningiomas)
-secondary brain tumours or gliomas
What is another type of stereotactic radiotherapy?
Radiosurgery
What is Radiosurgery?
- patients receive one single large dose of radiation
- IMRT - intensity-modulated radiation therapy
- IGRT - image-guided radiation therapy
Why might Radiosurgery be used?
If patients can’t undergo surgery
Why isn’t Radiosurgery not suitable for medium or large tumours?
Because there needs to be a consistency of exposure
What may radiosurgery cause?
Damage to nerves
What are atoms made up of?
Protons
Neutrons
Electrons
