E437: The effect of pre-operative radiotherapy on clinical outcome in retroperitoneal liposarcoma

A high rate of locoregional recurrence is one of the major difficulties in successful treatment of retroperitoneal liposarcoma (RLPS). Although pre-operative radiotherapy (pre-op RT) is considered a potential way to improve local recurrence, the effect of pre-op RT is still controversial. Hence, this study investigates the effect of pre-operative radiotherapy for RLPS.

Methods: A cohort of 205 patients with RLPS who had undergone both surgery and radiotherapy was analyzed for overall survival (OS) and local recurrence (LR). They were divided into three groups according to the radiotherapy scheme: 1) non-radiotherapy group, 2) pre-operative RT, and 3) post-operative radiotherapy.

Results: The non-RT, pre-operative RT, and post-operative RT groups contained 63 (30.7%), 41 (20%), and 101 (49.3%) patients, respectively. In the survival analysis, pre-operative RT (5 year, 82.6%) and post-operative RT (5 year, 64.4%) groups were demonstrated better prognosis than non-RT group (5 year, 23.8%). However, there were no significant differences in LR between the three group. In the analyses of factors affecting OS, histologic subtype (DDLPS, HR 16.64, p< 0.001) and R2 resection (HR 2.49, p=0.018) were risk factors in both univariate and multivariate analysis. In addition, in the pre-op RT group, there were patients who demonstrated rapid growth pattern of tumor (24.3%). Rapid growth tumor patients (3 year, 50%) showed poor prognosis than stable tumor patients (3 year, 92.6%).

Conclusions:

Pre-op RT showed better survival than the non-RT group, but was not conducive to local control. In addition, some patients showed a rapid growth pattern, and the prognosis was poor.