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CDHB

Radiotherapy

If a patient becomes unwell during a course of radiotherapy, even if the illness is unrelated to the oncological problem, the treating Radiation Oncologist should be contacted promptly.

• The side effects from radiation can be divided into acute and late effects. Acute side effects are those which occur during treatment and immediately after. Late side effects occur at least 6 months after treatment.
• Tissues which are rapidly proliferating (e.g., mucosal lining cells) tend to be the most sensitive to radiation treatment and express acute side effects. Patients being treated for a head and neck cancer for example, usually experience mucositis and have pain and difficulty swallowing about 2 weeks into the 6-7 week course of radiation treatment. Patients with rectal cancer often experience diarrhoea as a result of radiation damage to the gut lining cells. Patients being treated for a skin cancer may experience damage to the normal epithelial cells and the skin may develop erythema and in some cases sloughing and ulceration.
• These rapidly proliferating cells may also exhibit late side effects. The late side effects often involve fibrosis of tissues and scar formation. For example in the gut, fibrosis may develop leading to bowel obstruction or malabsorption. In the skin the late changes that may develop include thinning of the skin, scar formation and telangiectasia.
• More slowly proliferating tissues are more likely to develop late side effects so caution is taken to limit the dose of radiation treatment to these tissues. Examples of these late effects include:
  • Spinal cord: myelitis and subsequent development of neurological signs and symptoms.
  • Kidney: hypertension.
  • Optic nerve: optic neuritis and possible visual loss.
• Some tissues may exhibit subacute reactions which may not be evident during the treatment, but develop within a few weeks of it. For example a patient who has radiation treatment to the lung may present several weeks later with cough, dyspnoea and low grade fever and on imaging be found to have changes in the lungs consistent with radiation pneumonitis.
• In some instances the combination of radiation and cytotoxic chemotherapy may increase the risk of acute or late tissue reactions.
• Rarely, any tissue may undergo premalignant or malignant change years after exposure to ionizing radiation, e.g.:
  • Myelodysplasia and acute myeloid leukaemia.
  • Breast cancer after radiotherapy for Hodgkin's lymphoma.
• Patient information leaflets, which summarize important side effects of radiotherapy to different body sites, are available on HealthInfo (the public site) and HealthPathways.
• The challenge in radiation is to give the maximum dose to the tumour to optimize the chance of cure while sparing as much as possible the normal tissues to decrease the risk of acute and late side effects.

Topic Code: 17647