Outcomes of extraskeletal osteosarcoma patients and role of perioperative chemotherapy.

Abstract

11025 Background: Extraskeletal osteosarcoma (EO) is a rare malignant neoplasm that produces osteoid, bone, and chondroid material without direct attachment to bone or periosteum. The mainstay of treatment is surgical resection. We present our experience with EO, evaluating the role of chemotherapy. Methods: Records of all patients (pts) with EO seen between Jan, 1990 and Dec, 2014 were reviewed. All archived pathology slides were reviewed to confirm the diagnosis. Time-to-event analyses were performed from date of diagnosis and date of surgical resection using the Kaplan-Meier method. Results: Forty five pts with EO were included. Median age at diagnosis was 55 (range 8-81) years (y), and 58% were males. Frontline therapy was multimodal (90%) and included surgical resection in 41 (98%), chemotherapy in 28 (74%) and radiation therapy in 28 (68%) pts. Chemotherapy was predominantly anthracycline based, and included platinum in 22 (79%) pts. Eighteen pts received neoadjuvant chemotherapy. In those that received platinum, median necrosis rate was 50%, with 41% of the pts achieving > 90% necrosis. At the time of analysis, 29 (64%) pts were deceased, with 76% of those due to disease progression. Median follow up was 12 y (95% CI 10-14). Median overall survival (OS) and progression free survival (PFS) were 3.1 y (95% CI 2-7.5), and 1.5 y (95% CI 1-NR) respectively. 5-y OS and 5-y PFS were 43%. There was a trend towards longer OS and PFS in pts who received pre or post-op chemotherapy, and of those, platinum-based therapy was associated with a remarkably prolonged OS (median 15.1 vs. 1.7 y; 5-y 60% vs. 0%; p0.009) and PFS (median NR vs 0.9 y; 5-y 56% vs. 0%; p = 0.005). Baseline characteristics were similar in the platinum and non-platinum group. For 21 (47%) pts who relapsed, the median post relapse survival was 1 y (95% CI 0.8-1.5). In pts who received chemotherapy, the rate of relapse was greater in the non-platinum-based group (5 of 5 pts) as opposed to those who received platinum-based therapy, (9 of 22 pts, p = 0.04). Conclusions: Our results suggest a clinical benefit when platinum-based chemotherapy is incorporated in the management of pts with EO. We plan to explore this further with a multi-center retrospective study.