The Outcome of Patients With Localized Undifferentiated Pleomorphic Sarcoma of the Lower Extremity Treated at Stanford University.

Background: As a diagnosis of exclusion, Undifferentiated Pleomorphic Sarcoma (UPS) has unclear clinical characteristics. The objective of this retrospective cohort study is to investigate which clinical and prognostic factors of primary lower-extremity UPS will determine failure.

Methods: We retrospectively reviewed 55 primary lower-extremity UPS cases treated at Stanford between 1998 and 2015. Overall Survival (OS) and Disease-Free Survival (DFS) curves were calculated. Univariate Fisher's Exact Tests were used to examine relationships between disease recurrence, treatment, patient factors, tumor characteristics, and surgical margins.

Results: 5-year DFS and OS rates were 60% (95% CI, 45%-72%) and 68% (95% CI, 53%-79%), respectively. The 5-year DFS rate for patients with positive margins was 33.3% (95% CI, 5%-68%) compared with 63% (95% CI, 47%-76%) for patients with negative margins. (Log-rank, P=0.03). The OS rate for those with disease recurrence was 42% % (95% CI, 16%-67%) compared with 76% (95% CI, 59%-87%) for patients who did not have disease recurrence (log-rank, P=0.021). Local failure occurred more frequently with omission of radiation therapy (Fisher's exact test, P=0.009).

Conclusions: Positive surgical margins are an important prognostic factor for predicting relapse in UPS. Relapse of any kind led to worse OS. Radiation therapy improved local control of disease but had no statistically significant effect on DFS, highlighting the need for improved diagnostics to identify those at highest risk for hematogenous metastasis and for selection of patients for adjuvant systemic treatment.