(P 215) FEASIBILITY AND ADVANTAGE OF PRE-OPERATIVE RADIOTHERAPY IN RETROPERITONEAL SARCOMA

Objective: A high rate of locoregional recurrence is one of the major difficulties in successful treatment of retroperitoneal sarcoma (RPS). Various studies have demonstrated that the local recurrence rate can be improved with the use of adjuvant radiotherapy. However, the radiotherapy is associated with the treatment field toxicity, and thus its use in RPS is frequently challenged by the need for dose-limitation in the resected tumour bed where multiple radiosensitive organs reside, such as bowel, kidney, and liver. As a result, pre-operative radiotherapy (preRTx) has been considered an alternative option to improve the local recurrence rate while avoiding the radiation toxicity, yet concerns about the associated risk of post-operative complications need to be addressed. Hence, this study has been conducted to investigate the safety and effectiveness of pre-operative radiotherapy for RPS.

Methods: A cohort of 199 patients with RPS who had undergone both surgery and radiotherapy between October 2001 and February 2020 was reviewed and analyzed from a prospectively collected clinical database. They were divided into three groups according to the radiotherapy scheme: 1) preRTx group (n=23, 11.6%), 2) postoperative radiotherapy without tissue expander group (postRTx, n=89, 44.7%), and 3) postoperative radiotherapy with tissue expander group (postRTx+TE, n=86, 43.2%). We have analyzed the intra-operative findings, post-operative complications, and radiotherapy characteristics according to the groups.

Results: The preRTx was overall well tolerated and its use was not restricted by dose limitation. It did not affect the R2 resection rate, operative time, estimated blood loss, and the need for intra-operative transfusion. Moreover, there was no statistically significant difference in severe post-operative complication (Clavien Dindo Classification ≥ III) and re-operation rates amongst the three groups. However, the preRTx group was associated with higher incidence of post-operative transfusion and admission to intensive care unit (p=0.013 and p=0.036, respectively). Three patients required operative management for complications in preRTx group, two of whom developed complication after hospital discharge. In the multivariate analysis, the number of resected organs was the only independent risk factor for the development of severe post-operative complication. The radiation dose was highest in preRTx group (p< 0.001), although no significant difference was demonstrated in patient survival (p=0.634) and local recurrence rate (p=0.116) between the groups.

Conclusion: This study suggests that the neoadjuvant radiotherapy may provide an alternative management option for retroperitoneal sarcoma without compromising oncological resection or patient safety. Moreover, radiation dose elevation can be achieved if required. Nevertheless, further high-quality trials are warranted to evaluate the long-term outcomes and potential benefits of the pre-operative radiotherapy, including local recurrence and survival.