Natural history of undifferentiated pleomorphic sarcoma: Experience from the US Sarcoma Collaborative

Background Undifferentiated pleomorphic sarcoma (UPS) is a relatively rare but aggressive neoplasm. We sought to utilize a multi‐institutional US cohort of sarcoma patients to examine predictors of survival and recurrence patterns after resection of UPS. Methods From 2000 to 2016, patients with primary UPS undergoing curative‐intent surgical resection at seven academic institutions were retrospectively reviewed. Epidemiologic and clinicopathologic factors were reviewed by site of origin. Overall survival (OS), recurrence‐free survival (RFS), time‐to‐locoregional (TTLR), time‐to‐distant recurrence (TTDR), and patterns of recurrence were analyzed. Results Of the 534 UPS patients identified, 53% were female, with a median age of 60 and median tumor size of 8.5 cm. The median OS, RFS, TTLR, and TTDR for the entire cohort were 109, 49, 86, and 46 months, respectively. There were no differences in these survival outcomes between extremity and truncal UPS. Compared with truncal, extremity UPS were more commonly amenable to R0 resection (87% vs. 75%, p = 0.017) and less commonly associated with lymph node metastasis (1% vs. 6%, p = 0.031). R0 resection and radiation treatment, but not site of origin (extremity vs. trunk) were independent predictors of OS and RFS. TTLR recurrence was shorter for UPS resected with a positive margin and for tumors not treated with radiation. Conclusion For patients with resected extremity and truncal UPS, tumor size >5 cm and positive resection margin are associated with worse survival OS and RFS, irrespectively the site of origin. R0 surgical resection and radiation treatment may help improve these survival outcomes.