During radiotherapy, cancer cells are destroyed by using high-energy radiation. Treatment can be either external or internal depending on the site of the tumour. The dose and position of the radiation is carefully calculated so that normal cells receive as little radiation as possible, allowing them to recover with little or no long-term damage. The treatment is painless at the time, but side effects such as fatigue may develop as treatment continues. Radiotherapy may be used alone or with other cancer treatments.
External radiation is mainly carried out using a linear accelerator, which produces X-rays or electron beams. The type of radiation used depends on the type of cancer. The skin is usually marked with ink to ensure correct positioning of the patient. Treatment may be given once, several times a week, or several times a day, depending on the cancer and type of radiation used.
During this procedure, radioactive materials are placed directly into or around the cancer. For example, temporary radioactive implants may be placed within hollow organs, such as the uterus or vagina. Occasionally, a radioactive substance may be taken orally or injected into a body cavity. In some instances, small radioactive seeds may be placed directly into the affected organ and left in place while they gradually release radiation.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.