Treatment- Chemotherapy, Radiotherapy Flashcards
What are the stages of tumour growth?
Dysplasia
Cancer in situ
Invasion (detection threshold)
Onset of metastases
Cancer treatment- and what percentage for cure
solid tumours- not haematological
Chemotherapy (10%)
Radiotherapy (40%)
Surgery (50%)
What is the biological basis for radiotherapy
Damages DNA, destroying their ability to repair/ reproduce
Cancer cells have less ability to repair the damage than normal cells (tolerance)
How does radiotherapy protect normal healthy cells?
Fractionation
Dividing the total dose into daily fractions
Allows normal tissues to repair themselves better longer-term whilst ensuring damage to cancer cells
What beams are used in radiotherapy?
High powered Xrays
Millions MV of volts
The high beam x-ray is absorbed equally by bone and tissue
Electrons - skin
Protons- good for radiotherapy in sensitive areas (such as spine?)
What is palliative radiation therapy?
not curative or radical
relieve pain from bone metastases
spinal cord compression
vascular compression (SVC syndrome)
bronchial obstruction
bleeding from GI / gynaecological tumours
oesophagus obstruction (Cancer is causing an obstruction of food so this can provide some relief) (Alternative use is a stent)
Explain use of Palliative CT
DRR- computer removes the bone density imaging from the CT scan to degenerate an Xray which helps orientate and plan the radiation
to hit the target- treat one vertebra above and one below.
What dose is used in Palliative fractionation (Gy)
a small number of large fractions (the overall total dose is not high enough to cause significant damage)
(patient will not live long enough to get long term side effects- palliative)
single 8Gy (gray) 200G 5fractions
What dose is used in Radical / curative fractionation (Gy)
high dose spread over many fractions
65Gy 30fractions
70Gy 35fractions
longer duration of acute side effects but lower long term damage to organs
put in the same position for weeks. reference marks / tattoo.
CT simulation images are fused with MRI and PET to improve identification of cancer location.
What is a multi-leaf collimator?
plates that can be controlled by a computer. move them and ensure a treatment field which conforms to the SHAPE of cancer. (e.g square= catch healthy cells and damage them)
*avascular necrosis of head of the femur.
e.g. circle around the bladder, rectum for prostate cancer. volume in the bladder will change the prostate shape.
must be below 50 Gy.
Intensity Modulated Radiotherapy (IMRT)
A beam that arcs around the patient which avoids the critical structures and reduces side effects.
uses a changing beam intensity to achieve that.
uses MLC (multi-leaf collimator)
How does a proton beam design work?
When the beam enters the body, it delivers the dose at the same place. There is no exit dose because there is no energy left in the beams. Reduces side effects.
What are some common radiation side effects?
- Breast- swelling, skin redness
- Abdo- nausea, vomiting, diarrhoea
- Chest- cough, SOB, oesophagal irritation
- Head and neck- taste alt, dry mouth, mucositis, skin red
- Brain- hair loss, scalp redness, long term demyelination (somelence= dopey 4-6 weeks after tx)
- Pelvis- diarrhoea, cramping, urinary frequency, vaginal irritation
- Prostate- impotence, urinary symptoms, diarrhoea
- Fatigue.
*chemotherapy - systemic side effects.
Neoadjuvant induction treatment (chemo)
Curative/radical treatment categories:
- neo-adjuvant/induction tx = before the main treatment (shrinks- reduces the area so less risk of side effects to nearby structures with radiotherapy) (decreases the area of hypoxic tissue, increasing your chance of cure).
What are the four main types of curative/radical chemotherapy?
- neo-adjuvant / induction
- primary - unusual for solid tumours
- adjuvant = after the main treatment
- concurrent = with Radiotherapy (RT)
