Osteosarcomas in older adults: A report from the Cooperative Osteosarcoma Study Group.

INTRODUCTION: Osteosarcoma is typically a disease of the young, but may affect any age. Little is known about the disease in older patients beyond retirement age. We aim to describe the characteristics, treatment, and outcomes of older adult patients registered with our cooperative group. MATERIALS AND METHODS: The database of the Cooperative Osteosarcoma Study Group (COSS) was searched for osteosarcoma patients diagnosed from 1980 to 2020 who were aged 65 years or older at diagnosis. Affected individuals were analyzed for presenting factors, treatments employed, and outcomes. RESULTS: Fifty-five eligible patients were detected (median age 68 [range: 65-84] years; male:female = 25:30). Among these patients, 15/55 (27%) tumors were secondary malignancies, 41/55 (75%) were high-grade central, 4/55 (7%) surface, and 10/55 (18%) extraosseous malignancies, and all but three high-grade. Primary metastases were present in 15/55 (27%) patients. Surgery was reported for 46/55 (84%) patients, radiotherapy for 6/54 (11%, 1 unknown), chemotherapy for 42/50 (84%, 5 unknown). A complete surgical remission was achieved in 31/55 (56%). There were two toxic deaths. With a median follow-up of 1.7 (range: 0.1-18.0) years for all 55 patients and 2.2 (0.1-12.4) years for 24 survivors, event-free and overall survival at 2/5 years were 39.6% (standard error: 6.8%) / 24.5% (6.5%) and 62.0% (7.1%) / 32.7% (7.5%), respectively. Tumor site, metastatic status, surgery, and a complete surgical remission were prognostic for event-free and/or overall survival. DISCUSSION: Osteosarcomas can occur in older individuals. It is more often secondary, axially located, or extraosseous than in younger patients. However, the same treatment principles seem to apply, and selected patients may be cured. Multi-center cooperation is encouraged, thereby gathering expertise for such a rare disease presentation.