Undifferentiated pleomorphic sarcoma of bone (UPSB) treated in the German-speaking countries. A report of 132 unselected patients from the Cooperative Osteosarcoma Study Group (COSS)

PURPOSE: To describe Undifferentiated Pleomorphic Sarcoma of Bone (UPSB) treated in Germany, Austria, or Switzerland and using the same treatment-approach as for osteosarcoma. PATIENTS AND METHODS: The database of the Cooperative Osteosarcoma Study Group (COSS) was screened for UPSB. Eligible patients were evaluated for patient, tumor, and treatment related variables, and outcomes. RESULTS: One-hundred thirty-two eligible patients were identified (median age 41.7 (range: 10.3-74.6) years; males 58%; preceding malignancies 11%; tumor-sites extremities 86%, trunk 12%, head & neck 2%). Relative tumor size was < 1/3 of the involved bone in 83% of evaluable cases, pathologic fractures were present in 14% (limb-primaries only), and primary distant metastases in 6%. All patients received chemotherapy and 96% surgery for their primary (81% limb-salvage for extremity lesions). The response rate to preoperative chemotherapy was 38%. After a median follow-up of 3.9 (1 day-34.1) years for event-free and 5.2 (0.2-34.1) years for overall survival, the 5 year event-free and overall survival probabilities were 63% (standard error: 5%) and 70% (4%), respectively. Younger patient age, an extremity tumor, and localized disease predicted superior outcomes, pathologic fractures and limb-salvage surgery worse. The extent of tumor response to pre-operative chemotherapy seemed to have no impact on prognosis. DISCUSSION: UPSB generally affects considerably older persons than does the more frequent osteosarcoma. Despite a lower response rate to preoperative chemotherapy, its prognosis is at least comparable, if not better. Several prognostic factors impacting outcome could be defined. These results provide a benchmark for this rare disease.