Global Variations in Patterns of Care for Retroperitoneal Sarcoma.

Objective: To examine variations in patterns of care for retroperitoneal sarcoma (RPS) among sarcoma centres globally, including diagnostic work-up, surgical strategies and (neo)adjuvant therapies.

Methods: Retrospective analysis for primary RPS, from 19 RPS referral centres worldwide, prospectively collected within the RESAR repository (NCT03838718) between Feb 2017 - July 2022. Centres were categorised high volume (HVC) or low volume (LVC). Comprehensive resection (CR) was defined as en-bloc resection of ipsilateral kidney and colon.

Results: 1718 primary RPS were included. Preoperative biopsy was utilised frequently (median rate 98%) for solid (non-liposarcoma) RPS. In liposarcoma, the median rate of CR was 64%, with wide variation (IQR 37% [43%-80%], range 0-100%). There was greater variation in CR in liposarcoma in LVC (IQR 39.5% [40.5%-80%]) versus HVC (IQR 9.5% [58.3%-67.8%]). Perioperative chemotherapy was seldom used for liposarcoma (median 0%), with higher rates for leiomyosarcoma (median 10%) with high variation (IQR 26% [2%-28%]). Radiotherapy was used consistently infrequently in leiomyosarcoma (IQR 13% [0%-13%]. There was higher use of radiotherapy in HVC than LVC (median HVC 18.5% vs. LVC 5%). There was a significant decrease in radiotherapy use after the STRASS trial (pre 19% vs. post 14%, P=0.045).

Conclusions: Low variation was found in pre-operative biopsy of non-liposarcomas, use of chemotherapy in liposarcoma and radiotherapy in leiomyosarcoma, suggesting agreement between centres. There was high variation, suggesting equipoise, in the role of chemotherapy in leiomyosarcoma and the value of CR in liposarcoma. The STRASS study results seem to have been accepted, with a reduction in radiotherapy after its publication.