Clinical outcomes of non‐osteogenic, non‐Ewing soft‐tissue sarcoma of bone––experience of the Toronto Sarcoma Program

Non-osteogenic, non-Ewing soft-tissue sarcoma (NONE-STS) of bone is a rare presentation of primary bone cancers. Optimal treatments and outcomes for this heterogenous group are poorly described. We evaluated the factors associated with long-term outcomes in patients with this disease. Patients with localized NONE-STS of bone treated at the Toronto Sarcoma Program from 1987 to 2017 were identified. Clinical characteristics, treatment, and survival information were collected. Kaplan-Meier (log-rank) survival estimates from the time of definitive surgery, with uni-/multivariate analyses (Cox) of sarcoma-specific survival were performed. A total of 106 patients (60.4% male; median age 46 years) with NONE-STS of bone were identified. Common histologies included undifferentiated pleomorphic sarcoma [UPS]/malignant fibrous histiocytoma [MFH] (UPS/MFH, 41.5%), leiomyosarcoma (LMS, 20.8%), and fibrosarcoma (FS, 11.3%). Tumors were often high grade (59.4%) and involved the extremities (88.7%), with most receiving chemotherapy (67.9%) with cisplatin/doxorubicin-based regimens (73.6%). In the full cohort, 10-year DFS (45.7%, [95%CI: 35.7-55.8%]), OS (53.4%, [95%CI: 41.7-62.2%]), and SSS (63.9%, [95%CI: 53.9-72.5%]) were moderate. Histology specific, 10-year SSS was 70.7% [95%CI: 56.1-85.5%] for UPS/MFH, 51.8% [95%CI: 29.8-73.8%] for LMS, and 72.2% [95%CI: 45.1-99.2%] for FS. Only UPS/MFH (n = 4) showed sarcoma-related death >10 years. Multivariate analysis identified axial location (HR = 35.5, [95%CI: 3.4-369.6]), high grade (HR = 16.9, [95%CI: 1.6-185.1]), and disease relapse (HR = 485.1, [95%CI: 36.3-6482.6]) as risk factors for death (p < 0.05). Treatment with chemotherapy (HR = 0.1, [95%CI: 0.01-0.86]) and necrosis ≥85% (HR = 0.2, [95%CI: 0.04-0.99]) showed improved survival (p < 0.05). NONE-STS of bone has favorable long-term survival similar to osteosarcoma. Patients receiving chemotherapy derive benefit in retrospective analyses. UPS/MFH histologies show sarcoma-related death beyond 10 years. Further data on histologic subgroups are needed.