What is radiation therapy?
An often used and successful modality in the 'local' treatment of cancers
What is the problem with radiation therapy?
There is a risk of inducing a variety of human cancers
What cancer treatments are used to achieve local control of the disease?
What cancer treatments are uesd to treat disseminated disease?
What cancer treatments are used for pallitation?
Is radiotherapy delivered as a monotherapy?
How is radiotherapy used in conjuction with surgery?
It can be used before or after surgery
Why might radiotherapy be used before surgery?
To shrink tumour so that it is more operable
What are the types of radiotherapy?
- External beam radiotherapy
- Unsealed sources
What happens in external beam radiotherapy?
X-rays are generated externally, and precisely targetted into the body
What happens in bracytherapy?
A sealed radiation source is inserted into the body
What kind of emitters are used in brachytherapy?
Short range, only a few cm
What kind of radiation is used in unsealed source radiotherapy?
High energy, short range
Give two examples of medications used in unsealed source radiotherapy
- Radioiodine in thyroid cancer
- Meta-iodobenzylG in neuroblastoma
What allows unsealed source radiotherapy to work?
Some drugs/chemicals have an affinity for certain organs
What are the rules for all forms of radiotherapy?
- Maximise dose to tumour
- Minimise dose to normal tissue
What % of cancer patients require RT at some stage of their illness?
What % of those treated with radiotherapy are treated with curative intent?
What % of those treated with curative intent have an >5 year survival?
How can radiotherapy improve in the future?
- Improvements in tumour control
- Reductions in toxicity
- Early detection
- Increases in tumour sensitivity
What can x-rays and gamma-rays be thought of as?
Waves (λv = cc) or as photons (E = hcv)
What does the equation λv = cc tell you about x-rays?
As the frequency goes up, the wavelength must go down to keep Cc constant
What are photons?
Packets of energy
What do electromagnetic radiations (x-rays or gamma-rays) interact with?
The electronic component of matter
What can absorption of energy from radiation lead to?
- Excitation - loss of an electron to a higher level
- Ionisation - actual ejection of the electron
What happens when an electron is ejected in ionisation?
The molecule has an unpaired electron, and so is a free radical
What is a free radical?
A chemically reactive entity that causes chemical changes to exposed atoms and molecules
What damage can be caused by free radicals?
Lethal damage or mutation
What kind of damage is good in terms of radiotherapy?
Lethal damage, as want to kill the tumour cells
Why it mutation bad in radiotherapy?
Because there is a change in function, which can be detrimental in a normal cell