1675PDEURO-B.O.S.S.: Outcome in rare non-osteosarcoma bone sarcoma

Abstract Background The EUROpean Bone over 40 Sarcoma Study included patients with 41 to 65 years of age with primary malignant bone sarcoma treated with intensive multiagent chemotherapy. Outcome in the subgroup of high-grade osteosarcoma has been published (Ferrari et al. 2017). This report focuses on other bone sarcomas representing the largest prospectively collected dataset based on an international consortium. Methods Chemotherapy was based on doxorubicin, cisplatin, ifosfamide, and methotrexate. Tumors registered as MFH, sarcoma NOS, spindle cell sarcoma or undifferentiated sarcoma were grouped as „undifferentiated pleomorphic sarcoma“. Further histologies included leiomyosarcoma, fibrosarcoma and angiosarcoma. Results 122 patients with other bone sarcoma were registered into EURO-B.O.S.S. and 113 considered evaluable for analysis. Their median age was 52 years (range: 40-66). Eighty-eight bone sarcomas were grouped as UPS, 20 were leiomyosarcomas, and 5 had other histologies (3 fibrosarcoma, 2 angiosarcoma). Chemotherapy according to the EURO-B.O.S.S. recommendations was initiated in all patients. Surgery was performed for 109/113 tumors, prior to chemotherapy in 13, delayed in 96. A macroscopically complete surgical remission of the primary tumor site was obtained in 106/113. At last follow-up, 70 patients were alive, 62 of these in complete remission and 8 with bone sarcoma. Of 43 patients who had died after a median of 2.1 years (0.15-8.8), 37 were reported to have died of progressive bone sarcoma, 2 of other causes (1 neutropenic sepsis, 1 secondary malignancy (myeloma)) and 4 of unknown causes. Table . 1675PD n 5y-EFS p-value 5y-OS p-value Histology UPS 88 44.90% 62.40% Leiomyosarcoma 20 32.50% 0.146 52.00% 0.710 other 5 Site extremity 83 49.40% 66.90% non extremity 30 29.90% 0.01 46.80% 0.002 Primary surgery yes 13 25.60% 43.00% no 96 48.10% 0.112 65.00% 0.042 Response (in 78) good 26 71.60% 71.50% poor 52 38.90% 0.003 57.40% 0.083 Conclusions Multiagent chemotherapy was feasible in this patient population. Outcome seems comparable to high-grade osteosarcoma with a non-significant trend for UPS over leiomyosarcoma. Favorable outcome was associated with extremity site, secondary surgery after neoadjuvant chemotherapy, and good response to primary chemotherapy. Legal entity responsible for the study The authors. Funding COSS, SSG, ISG. Disclosure P. Reichardt: Honoraria (institution), Advisory / Consultancy, Research grant / Funding (institution): Novartis; Honoraria (institution), Advisory / Consultancy: Pfizer; Honoraria (institution), Advisory / Consultancy: Bayer; Honoraria (institution), Advisory / Consultancy: PharmaMar; Honoraria (institution), Advisory / Consultancy: Lilly; Advisory / Consultancy: Clinigen; Advisory / Consultancy: Deciphera; Advisory / Consultancy: Roche; Honoraria (institution): Amgen. R. Bertulli: Honoraria (self), Speaker Bureau / Expert testimony: Lilly; Honoraria (self), Speaker Bureau / Expert testimony: Italfarmaco; Honoraria (self), Speaker Bureau / Expert testimony: PharmaMar. All other authors have declared no conflicts of interest.