Radiotherapy for benign conditions tends to use simpler techniques and lower doses than that used to treat cancer.
Radiotherapy for benign conditions tends to be delivered by either X-rays or electrons. The technique and type of treatment used will depend on the condition and the site of the disease. Often, although not always, the doses of radiation used are much lower than that for cancer, so result in fewer side-effects and tend to require more simple radiation techniques than those used for cancer.
The Royal College of Radiologists (UK) published a review of the use of radiotherapy for benign conditions in 2015 and cited evidence and guidelines for its use in conditions of the brain, head and neck, eye, musculoskeletal and skin/soft tissues.
Radiotherapy can lead to a small chance of causing cancer. The specific risk depends on many factors, such as dose, body site, volume of tissue treated and the age of patient. For patients with benign conditions, the risk may be negligible (e.g. for older patients where there is treatment to the extremities), or may be prohibitive (e.g. when treating children to cancer-bearing regions). This is covered in great detail in a recent paper about intermediate-dose radiotherapy (McKeown et al) and in the German (DEGRO) benign radiotherapy guidelines.