Osteosarcoma of the Humerus Developing as Second Malignancy in the Irradiation Field Outside the Primary Tumor: 11 Years after Ewing Sarcoma of the Scapula and 29 Years after Breast Cancer

Purpose: Development of sarcoma is a known late rare negative side effect of radiotherapy. We add two cases to emphasize the need for open-end follow-up and critical evaluation to avoid misinterpretation. Patients, Methods, and Results: Two patients developed osteosarcoma as a second malignancy in the humerus after adjuvant radiotherapy of a primary tumor not directly involving the later affected bone. The first patient had a Ewing sarcoma of the scapula at age 13 years. Though after neoadjuvant chemotherapy the resected specimen showed only fibrotic necrotic areas within clear resection margins, the study group indicated adjuvant radiotherapy in a field including the shoulder joint. At age 24 years she developed an osteosarcoma of the humeral head, which was resected and reconstructed with a proximal humerus endoprosthesis. She is alive without disease at age 32 years. The second patient presented with an osteosarcoma of the proximal humerus 29 years after irradiation for breast cancer including the shoulder joint. The sarcoma was misinterpreted as radiation-induced necrosis and the patient was treated with a reverse shoulder endoprosthesis. Pathologic examination of the resected humeral head then showed a typical osteosarcoma. Two years later the humeral reverse shoulder implant was resected and a proximal humerus tumor prosthesis implanted leaving the original glenosphere. Conclusions: In both cases radiation-induced osteosarcoma developed in bone not affected by the primary cancer. Protecting uninvolved structures must be warranted in the planning of radiotherapy. The long latency between the primary and second cancer mandates long-term—best indefinite—follow-up, as with appropriate treatment of a radiation-induced osteosarcoma good healing rates comparable to those of primary osteosarcoma can still be achieved.