Although there are total-body and half-body techniques where low doses are delivered to wide areas for specific purposes such as obliterating the bone marrow prior to transplantation, or palliating widespread bone pain, most radiotherapy is given to localised areas. This means that the side effects will depend on the tissues irradiated and be confined to the area of the body receiving the radiation. The damage to tissues tends to accumulate with each fraction of radiotherapy. The acute effects will occur towards the end of the course of therapy and resolve within days to weeks. More important are the late effects which signify more permanent tissue damage. It is the late effects that may be avoided by altering the fractionation schedule. Let us look at what side effects you may expect from irradiating various tissues.
Skin reactions occur when tumours near to the skin surface are irradiated. An example would be radiotherapy for breast cancer. With higher-energy irradiation the peak dose is well beneath the skin and so skin reactions are less common if deep-seated cancers are being irradiated. The immediate or acute reaction occurring towards the end of a course of radiation is a redness of the skin followed by itchy dry skin peeling or, if more severe, weeping ulcerated skin like a very bad sunburn.
This will heal just like a sunburn and creams can be used to control the discomfort. If there is any hair in the field, hair loss will occur, and the sweat glands may dry up in the area treated. If there are late effects, these will include tanning or loss of pigmentation of the skin, a woodiness of the skin and the appearance of multiple small blood vessels just under the skin. The skin may remain more sensitive to sun exposure. With severely affected skin, ulceration and difficulty in healing when cut can occur, because of damage to the skin’s blood supply.
Mouth and bowel
Similar burning side effects are the acute side effects in other areas. There is loss of taste, and mouth ulcers and dryness in the mouth occur. Mouthwashes for symptom control can be used until healing occurs. Dry mouth is often a long-term result of radiation to the mouth. Dental work, particularly extractions, should be done prior to radiotherapy with time for healing, to prevent permanent damage to the jaw-bones.
Lower down, if the oesophagus is irradiated, patients will experience pain on swallowing. If the stomach and small bowel are in the field of irradiation, nausea and vomiting may result. Inflammation of the large bowel may result in pain, bleeding and diarrhoea. All acute effects should reverse within a couple of weeks but it can be a serious problem if these are late effects, indicating more profound tissue damage.
Brain and spinal cord
Above a certain radiation dose, damage to the brain or spinal cord is likely. This is called the tissue’s tolerance to radiation. The tolerance level is well known and radiation is planned not to exceed this dose. Acute side effects include a somnolence syndrome six weeks after irradiation of the brain, particularly in children, when patients feel excessively sleepy for a couple of weeks, and then recover. After spinal cord irradiation, some patients experience temporary shooting sensations down the body when bending the neck. Late effects in these tissues — which actually result from permanent damage to the nervous system tissues — may cause symptoms that mimic having a brain tumour or a cancer pressing on the spinal cord.
Other late effects may depend on what other organs are irradiated. If the lens of the eye receives too high a dose when irradiating the brain, cataracts will develop. Late endocrine problems can be caused by irradiation of the pituitary gland at the base of the brain because of the decreased hormone output from the gland. A similar picture is seen with late occurrence of an underactive thyroid after irradiation of the neck.