Medical aspects of radiotherapy Flashcards
What is radiotherapy?
The use of high energy X-rays to kill cancer cells and shrink tumors.
There are two types of radiation therapy, namely:
- external beam radiation
- internal radiation therapy
What is the difference between the two?
- External beam radiation → machine aims radiation (beam of X-rays outside of the body) at the cancer, as a local treatment.
- Internal radiation therapy → involves the injection/placement of radioactive materials in the body. With this, a larger dose of radiation can be given because the radiation is given directly to the cancer cells and less to the nearby healthy cells.
Name a specific type of internal radiotherapy and describe it.
Brachytherapy.
Here, a sealed container with a radioactive substance is directly placed into the tumour (i.e. implant). Depending on the type of inplant, the radiation source will stay in place for minutes, hours or days, or permanently.
Brachy = Brakhu in Greek = short distance
For what kind of tumors is brachytherapy mostly used?
Gynecological and urologic tumors
Explain the risks that are associated with radiotherapy.
- Radiotherapy causes side effects
- It also increases the chances of the development of a second cancer later in life → greater benefit vs a small risk
- While external beam radiotherapy does not give any radiation off after the treatment, this is not the case for internal radiotherapy. During internal radiotherapy, the patient can give off radiation (not safe for people arround patient).
Complete the sentences.
- In 2021, … new patients were diagnosed with cancer.
- … of these patients will get radiotherapy.
- … of these patients will get radiotherapy with the intend to cure them.
- In 2021, 124.000 new patients were diagnosed with cancer.
- 2/3 of these patients will get radiotherapy.
- 2/3 of these patients will get radiotherapy with the intend to cure them.
What is the goal in regard to cancer radiotherapy for:
- primary treatment
- before other treatment
- after other treatment
- to relieve symptoms
- primary treatment → to get rid of all the cancer
- before other treatment → to shrink the cancer
- after other treatment → to destroy the remaining cells
- to relieve symptoms → palliation
What is discussed in the first consultation with a radiation oncologist?
- Medical history
- Complaints
- Review of the imaging of the patient
- Goal of the treatment
- Side-effects and risks of treatment
- Explanation of workflow
- Follow-up afterwards
On the planning CT or MRI scan, the radiation oncologist delineates some crucial things to take into account before radiotherapy. Name and describe these things.
- Gross tumor volume (GTV) → position and extent of the tumour
- Clinical target volume (CTV) → tissue volume that contains the GTV and subclinical microscopic malignant lesions
- Planning target volume (PTV) → CTV plus a margin to allow for geometrical uncertainty in its shape and variations in its location relative to the radiation beams due to organ mobility, organ deformation, and patient setup variations.
Of the gross tumor volume (GTV), clinical target volume (CTV) and planning target volume (PTV), what is the most important to be treated?
The aim of radiotherapy is to always treat the CTV.
What is needed to be taken into account in regard to the prescription (how radiotherapy is going to be delivered/what site)?
- Each different type of cancer, different regimen.
- Every single tissue, different tolerance to radiotherapy.
- Duration of the treatment (single or several)
- This also determines what (kind of) side effects there are.
What are unintended but unavoidable effects of radiotherapy?
- Early side effects seen by fast dividing tissues (< 90 days) e.g. the skin and mucous membranes.
- Late side effects seen by slow dividing tissues (>90 days) e.g. central and peripheral nervous tissue or cardiac tissue.
What is important to take into consideration in regard to the following when targetting the tumour specifically?
- Full dose
- Total dose
- Dose per fraction
- Total treatment time
- Full dose → is divided in number of small doses (i.e. fractions)
- Total dose → total dose differs based on the type of tumour
- Dose per fraction → varies per tumor site
- Total treatment time → differs based on type of tumor (head and neck tumour low dose every day for 6 weeks vs small lung tumor 1 day with high dose)
What is important to take into consideration when treating a patient in regard to:
- Prognosis
- Volume of target
Also name 1 other factor that influences the treatment of a patient.
- Prognosis → curative vs. palliative intention
- Volume of target → bigger volume means more fractionation, but also there is a need to be more careful due to the extra surrounding tissue.
- Age, condition, wishes of the patient
1/3 of the treatment with radiotherapy is palliative. For what is palliative radiotherapy effective?
Palliative radiotherapy aims to shrink cancer, slow down its growth or control symptoms. It doesn’t aim to cure cancer. It is therefore effective to target:
- pain
- bloodloss
- compression of tumor on myelum or bowel
Is surgery here an option? What would you do?
No, surgery is not an option due to the tumour compressingn the myelum (i.e. the spine). This surgery would be way too risky and therefore radiotherapy is the best option.
