Introduction & Background: Today, radiotherapy alone or in combination with other therapeutic methods for treatment of various cancers is very effective and has a special place in medicine. This treatment modality is used in two ways, in combination with radiopharmaceuticals and in the vicinity of tumors, or by irRADIATION of tumor bed from an external source. One of the unwanted effects of this type of treatment is its effect on the musculoskeletal sys-tem. Considering the better long term survival of cancer patients and the appearance of late-onset side effects of those malignancies, knowledge about the effects of radiotherapy on the musculoskeletal system and the methods of differentiating them from secondary involvement by malignant diseases, has gained significant importance.