(P 348) RESECTION OF RECURRENT RETROPERITONEAL SOFT TISSUE SARCOMAS: ARE INTENSIVE MULTIMODAL TREATMENTS ASSOCIATED WITH INCREASED PERIOPERATIVE MORBIDITY?

Objective: Surgical resection is the preferred treatment for local recurrence of retroperitoneal soft tissue sarcomas (RPS). In high-risk tumours, this is often carried out as part of multimodal therapy approaches, which may include radiotherapy, systemic therapy, and – in some centers – regional hyperthermia. Our study aimed to identify clinical, surgical, and therapy-related risk factors for perioperative morbidity following the resection of recurrent RPS within intensive multimodal treatment protocols.

Methods: This study collected clinical characteristics, neoadjuvant therapies, and perioperative complications for patients who underwent surgery for RPS recurrence at our centre between September 2009 and March 2021. The Comprehensive Complication Index (CCI) was calculated for each tumour resection. To account for the specific distribution of CCI values, a zero-one-inflated-beta model for the occurrence of any complication (CCI > 0) and a separate model for 0< CCI < 100 were created and used to analyze the relevance of clinical, surgical, and therapy-related risk factors.

Results: The analysis included 182 patients (91 male, 91 female) who underwent surgery for relapsed RPS. The median CCI was 20.9 (range 25%: 0; 75%: 44.9), and it appeared to be higher in patients who underwent neoadjuvant radiotherapy (31.55 (3.05; 42.93) vs 20.9 (0; 45.57) or regional hyperthermia (33.5 (0; 59.2) vs 22.6 (0; 37.08). In a zero-one-inflated-beta model for the occurrence of any complication after recurrent resections (CCI > 0), only the number of resected organs was found to be a significant factor (RR for resection of ≥ 3 organs vs < 3 organs: 1.59 ((1.18, 2.38), p = 0.002). Preoperative therapies, gender, age, transfusion requirements and the number of recurrences had no significant influence on CCI values. This was confirmed in the second model for 0< CCI < 100.

Conclusion: Patients undergoing resections of recurrent RPS experienced postoperative morbidity comparable to primary resections. Operative factors, such as the number of resected organs play a decisive role, while the influence of previous therapies is of secondary importance. Recurrent resections of RPS can be safely performed within the framework of multimodal therapy approaches, but the potential morbidity risk of multivisceral resections should be considered. The CCI is a useful tool to precisely describe perioperative morbidity in sarcoma surgery. Zero-one-inflated beta models can be used to analyze the disproportionate distribution of CCI values.