Cancer Radiotherapy Flashcards
Principles governing clinical decisions
Principles governing clinical decisions:
- Tumour factors: differentiation of tumour, different to host so harder to treat. Growth rate of tumour, doubling time (shorter time makes it more aggressive)
- Patient factors: age, ethnicity, socioeconomic background
Treatment modalities available: cyber knives, proton knives, postcode lotteries, travel to treatment
How is cancer treated?
How cancer is treated:
- locally: Surgery or radiotherapy
- Systemically: Chemotherapy, hormone therapy, biological therapy, radioactive isotopes (thyroid cancer)
Cancer Surgery
Cancer surgery:
The oldest method of treating malignant
disease.
Primary treatment of choice
Conservative surgery
e.g. lumpectomy
Radical surgery
e.g. dissection of tongue
& associated nodes
Palliative surgery
e.g. bowel resection
tracheostomy
Chemotherapy – Treatment of choice
For which cancers?
Chemotherapy – Treatment of choice for:
Acute & Chronic Leukaemia
Testicular teratoma
Small cell lung cancer
Hodgkin’s lymphoma (advanced)
Non-Hodgkin lymphoma (advanced)
What is radiotherapy?
Radiotherapy:
The accurate delivery of precise doses of
ionising radiation to treat certain diseases
it cures more people than chemotherapy and
is 13 times more cost effective
It helps cure 40-50% of cancer patients
When used palliatively it is effective for
symptom control, improved quality of life and
sometimes extends life
- Must be administered in same position
- Usually used in combination with other therapies such as chemotherapy
How does radiotherapy work?
How radiotherapy works:
- X-rays contain packets of energy
- As the X-rays pass through the body, some energy is
transferred to the cells by absorption
This excess energy disturbs cell function, leading to cell damage & death
radiation damages the cell’s DNA
This action is either direct or indirect
Cancer cells have a diminished ability to repair this damage Thus continued damage = Cell death
Why isn’t radiotherapy delivered in one session?
Radiotherapy not delivered in one session because cells that are not in mitosis need to be considered.
Surrounding cells dose tolerance needs to be considered.
Radiotherapy aims: Palliative
Radiotherapy aims: Palliative
To relieve symptoms & improve quality of life
Short treatment courses (1-10 fractions)
Simple treatment techniques
Low dose usually means consideration of side
effects is not an issue
Low total dose Usually used alone
- Usually 5 days for 2 weeks
Radiotherapy aims: Radical
Radiotherapy aims: Radical
Aim to cure
Typically longer fractionations (15-40 fractions)
Recent evidence for breast and prostrate cancers has changed this to shorter regimens (can be shorter, side effect may be worse)
Complex planning & techniques
Reduces dose to surrounding organs to minimise side effects
Medium to High total dose
Often combined with other treatment modalities (e.g.
chemoradiation)
How many times is radiotherapy administered in bladder and bowel cancer?
Radiotherapy is usually administered:
45 times in bladder cancer
60-70 times in bowel cancer
When is radiotherapy used instead of other options?
Radiotherapy is used instead of other options when:
Accessibility- When surgery would cause too much morbidity, e.g. larynx
Cosmetic effect- When surgery would be too disfiguring, e.g. neck dissection for
oral cancers
Anaesthetic risk- Patient is too old for safe surgical procedure or reactive to anaesthetics (allergies)
if patients cannot tolerate chemotherapy (might be resistant) due to adverse reactions or severity of likely side effects
where research evidence suggests better outcomes than other modalities for
specific cancers (e.g. early Hodgkin lymphoma: sensitive to radiation)
Because patient chooses it
When isn’t radiotherapy used?
Radiotherapy isn’t used on:
- Previously irradiated areas as most tissues have a tolerance dose. Long term damage could be caused
- For widespread or systemic disease- RT to large areas causes unacceptable side effects (nausea and vomiting caused by breakdown). Small areas only
- Where irradiation to surrounding normal tissue causes morbidity- e.g. compromise to lymphatic drainage in patients with breast cancer
Pathophysiology of radiation reactions
Pathophysiology of radiation reactions:
Occur in ‘normal’ tissues within the irradiated area Acute reactions occur due to cellular loss
Radiation interrupts mitosis or damages DNA of stem cells
Healing depends on recovery of stem cells
Products of cell signalling and cell killing interact with macrophages and lymphocytes
causing erythema, nausea etc.
Chronic reactions occur due to permanent loss of stem cells, necrosis/fibrosis of
irradiated tissues.
Why do acute radiation reactions occur?
Acute radiation reactions occur due to cellular loss:
- Radiation interrupts mitosis or damages DNA of stem cells
- Healing depends on recovery of stem cells
- Products of cell signalling and cell killing interact with macrophages and lymphocytes
causing erythema, nausea etc.
Why do chronic radiotherapy reactions occur?
Chronic radiotherapy reactions occur due to :
- Permanent stem cell loss
- Necrosis or fibrosis of irradiated tissues
