3. Radiotherapy Flashcards
What are the stages of carcinogenesis?
- Initiation
- Promotion
- Progression
- Metastasis
What is a carcinogen?
Exposure agent. E.g chemical agents, radiation, particulate matter, viruses.
What happens in inititiation?
Irreversible, inheritable mutation or damage to cell DNA due to carcinogens, or error in DNA replication.
In order to fix initiation it must survive normal mechanisms to detect + repair errors in DNA replication.
Occurs soon after exposure to carcinogen.
What occurs in promotion?
The process of an initiated cell developing into a malignant neoplasm.
~ mutated cell is exposed to agents (promoters) that enhance growth of tumour.
Occurs over a long period following initiation.
How do promoters enhance the growth of the tumour?
Inhibit expression of tumour suppression genes. E.g. hormones, drugs.
Increase expression of growth factors.
What occurs in progression?
Genetically modified cells continue to grow throughout the tissue of origin, due to continuing evolution of genetic mutations.
Causes tumour to increase in size and histological grade.
What is histological grade?
Describes a tumour in terms of how abnormal tumour cells are.
(1- very similar to normal cells, 3 - very abnormal).
How does metastasis occur?
Tumour cells travel from initial tumour site to other parts of the body.
~ requires cells to break free from primary tumour.
~ release of protease enzymes enhance chance of metastasis as they break down the extra-cellular matrix surrounding adjacent cells.
Where does metastasis occur?
Via blood vessels or lymphatic system
What is the route to metastasis?
Capillary bed is encountered by mobile tumour cells - these determine probable site.
If cell can colonise in new organ, metastasis will develop.
~ requires cell to be able to reproduce in new environment
~ cell must be bale to promote angiogenesis
Lungs and liver are common sites of metastasis.
What is angiogenesis?
Formation of new blood vessels that feed the tumour with oxygen and nutrients.
What can reduce the risk of cancer?
Understanding genetic factors, minimising exposure to carcinogens, vaccinations from viruses.
How can cancer be diagnosed?
Biopsy, blood tests, imaging.
How can diagnostics be used to evaluate the extent of the disease?
- staging
- pathology: histological grade and stage
- imaging: size and stage of tumour
Determine suitable treatment: localised or metastasised, radical or palliative.
What are the therapy options?
Watch and wait, surgery, systematic anti cancer therapy (SACT), radiotherapy options.
What different radiotherapy options are there?
External beam RT, Brachytherapy, radioisotopes
What does radical and palliative mean in radiotherapy?
Palliative - aims to control symptoms where curing is not possible.
Radical - shrink + control growth of tumour with the aim to cure.
What is adjuvant radiotherapy?
When radiotherapy is used after primary treatment to improve outcome.
What is neoadjuvant radiotherapy?
When the aim is to shrink the tumour prior to treatment
What can chemoradiotherapy lead to?
Improved lead control, but increased potential for toxicity.
How does radiotherapy damage cancer cells?
Energy from radiation damages DNA in both tumour and healthy tissue.
Explain Image guided radiotherapy (IGT).
Acquiring an image to position patient, prior to treatment.
Explain Intensity Modulated Radiotherapy (IMRT)
Method of sculpting the radiation dose to the target.
Define neoplasm/tumour.
Tissue resulting from the process of altered cell differentiation + growth.
Define benign neoplasm.
Tumour cells clustered into single mass, unlikely to spread.
Define malignant neoplasm.
Tumours with ability to mestasise.
Define progression.
Further growth + spread of tumour cells to other parts of body
