Neoadjuvant radiotherapy for primary retroperitoneal well-differentiated liposarcoma: a Transatlantic Australasian Retroperitoneal Sarcoma Working Group (TARPSWG) propensity score matched analysis.

Background With negligible risk of distant metastasis, the primary treatment focus in patients with primary retroperitoneal well-differentiated liposarcoma (pRP-WDLPS) is local control. The recently completed phase 3 STRASS trial suggested a potential benefit to neoadjuvant radiotherapy (RT) in optimizing local control in these patients. This study investigates outcomes associated with neoadjuvant RT in a larger cohort of patients undergoing surgery for pRP-WDLPS.Methods In this study from 24 participating sites, we retrospectively identified all patients with pRP-WDLPS who underwent curative-intent resection between January 1, 2002 and December 31, 2017. The primary endpoint was the cumulative incidence function (CIF) of local recurrence (LR), and the secondary endpoint was overall survival (OS). The impact of neoadjuvant RT on the CIF of LR was analyzed using a 1:2 propensity score matching (PSM).Findings Of 582 patients included in the entire cohort, 72 patients (12%) received neoadjuvant RT. The 1:2 PSM group included 208 patients of which 138 patients (66%) underwent surgery alone and 70 patients (34%) underwent neoadjuvant RT and surgery. With a median follow up of 73 months, the 5- and 8-year CIF of LR for neoadjuvant RT and surgery group was 6% and 10%, respectively, and 26% and 33%, respectively, for the surgery alone group (odds ratio (OR) 0·85, 95% confidence interval (CI) 0·76-0·97, P < 0·001). The 5- and 10-year OS for the neoadjuvant RT and surgery group was 92% and 80%, respectively, and 84% and 71%, respectively, for the surgery alone group (HR 0·50, 95% CI 0·27-1·21, P = 0·07).Interpretation To the best of our knowledge, this is the largest study to report outcomes of neoadjuvant RT for pRP-WDLPS. Neoadjuvant RT was associated with a significant decrease in LR compared to surgery alone. These data further validate the use of neoadjuvant RT for pRP-WDLPS.Funding Funding was received from the Susan and Habib Gorgi Family Fund for Sarcoma Research.