Defining an Unresectable Primary Retroperitoneal Sarcoma.

Background: Retroperitoneal sarcomas (RPS) comprise a heterogenous group of rare mesenchymal tumours. A complete macroscopic en bloc resection of the tumour with involved adjacent structures is the only curative treatment modality. There remain no consensus criteria regarding the definition of a resectable versus unresectable RPS. This study examined the rate, rationale and outcomes for resectable and unresectable RPS from a single large tertiary referral centre.

Methods: All patients with primary non-metastatic RPS referred between January 2017 and March 2023 were identified. Patient and tumour details as well as survival analyses were compared between resectable and unresectable cohorts, and factors for unresectability were analysed.

Results: A total of 104 patients were considered for the analysis, of which 91 (87.5%) were resectable and 13 (12.5%) unresectable. Gender, age, tumour size and side were similar in both cohorts. Unresectability was determined on pre-operative imaging in seven patients (53.8%) and intra-operatively in six (46.2%) patients. The most common technical cause for unresectability was the involvement of superior mesenteric vessels (38.5%). At a median follow-up of 18 months, 84.6% of the unresectable cohort and 8.8% of the resectable cohort had died.

Conclusion: Approximately 12% of patients with primary RPS were unresectable at presentation, and in most cases, unresectability can be determined pre-operatively. Defining resectable and unresectable disease may improve the prognostication and management for patients with primary RPS.