The side effects of radiation therapy can be split into two broad categories: early and late effects.
Early side effects are usually observed within two weeks after starting radiation therapy and can continue up until one month after the treatment has begun. These effects are usually inflammatory, with areas such as the skin and mucous membranes being the most commonly affected. Redness, irritation, and ulceration of the treated surface can develop.
The early side effects are dependent on the tumour, its location, and the surrounding tissues that may be involved. Some other possible effects are described below:
- Delayed hair regrowth and/or regrowth of a different colour. If dark-coloured, it may be much lighter (even completely white); if light-coloured, it may be much darker.
- If the mouth is being treated, side effects can include excessive salivation, bad breath (halitosis), formation of plaques or ulcers, and secondary infections.
- If the eye is being treated, side effects such as blepharitis, conjunctivitis, and keratitis (inflammation of the eyelids, surface of the eye, and cornea respectively) are possible. The eye can become dry due to a change in normal tear production and is susceptible to corneal ulceration (an open sore on the cornea). Cataracts and retinal damage are also possible and may lead to loss of vision.
- If the intestinal tract is within the radiation field, diarrhoea may also be observed.
Late side effects usually occur more than six months after therapy. These effects are also dependent on the tumour and the surrounding tissues that may be involved.
Contributors: Debbie Stoewen DVM, MSW, RSW, PhD; Christopher Pinard, DVM