Our study aimed to describe the clinical features of undifferentiated pleomorphic sarcoma (UPS) and identify the predictors of poor outcomes.

Patients and methods:
The clinicopathological variables and treatment strategies of 100 UPS patients who underwent surgical resections at a single institution between November 2004 and July 2016 were reviewed. Kaplan-Meier and Cox regression method were conducted for survival analysis.

The median follow-up time was 94 months (range, 1.5-154 months). R0 resection was applied for 72 cases, and the median tumor size was 5.75cm (range, 1-30cm). Tumor grades of 45 patients were intermediate grade (G2), and 54 patients were with advanced stage (stage III/IV). Twenty-seven patients presented with tumors involving important structures, in which the nerve was the most frequently invaded structure (n=12). During the follow-up, 40 patients suffered from postoperative local recurrence, and distant metastasis was observed in 25 patients which mainly metastasized to the lung (n=14). The 5-year OS rate, 5-year LRFS rate, and 5-year MFS rate was 53%, 55%, and 70%, respectively. Multivariate analysis revealed that tumor presentation, tumor size, and important structures involved (p=0.033, p=0.004, and p=0.033, respectively) were independent prognostic factors associated with OS. Meanwhile, age, resection quality and tumor grade were independent prognostic factors for LRFS (p=0.033, p=0.045, and p=0.007, respectively) and tumor depth was significantly associated with MFS (p=0.050) in multivariate analysis.

Primary treatment of UPS should be conducted by experts in large sarcoma center. Wide surgical margin provides sufficient control of the disease recurrence.