A Japanese Multicenter Database Study of Retroperitoneal Sarcoma: Outcomes of Patients Receiving Eribulin Therapy

Clinical evidence on disease characteristics and outcomes of retroperitoneal sarcoma (RPS) remains limited. Although eribulin was approved for soft tissue sarcomas in Japan in 2016, real-world data on its use for advanced RPS are scarce. We investigated treatment patterns and survival outcomes of patients with RPS, with a particular focus on those receiving eribulin.

The database included 118 patients pathologically diagnosed with RPS between January 2000 and August 2025. Clinicopathologic data, including inflammation/nutrition markers and survival outcomes, were analyzed.

Among them, 102 (86%) underwent surgical resection of the primary tumor, with a median recurrence-free survival of 20 months and a median overall survival of 9.2 years. Well-differentiated liposarcoma, dedifferentiated liposarcoma, leiomyosarcoma, and undifferentiated pleomorphic sarcoma were the most frequent histologic subtypes. Non-well-differentiated liposarcoma histology, Stage IIIA-IIIB, lower C-reactive protein-albumin-lymphocyte index, and higher modified neutrophil-platelet score were associated with poor postoperative prognosis. Of 44 patients with unresectable RPS who received systemic therapy, 23 (52%) were treated with eribulin. In this group, complete response, partial response, and stable disease rates were 4.3%, 26%, and 35%, respectively. The most common adverse events were decreased neutrophil count (40%), peripheral neuropathy (30%), and dysgeusia (20%). Multivariate analysis showed that non-use of eribulin and undifferentiated pleomorphic sarcoma were independently associated with worse survival in unresectable disease.

We separately described outcomes and treatment patterns of patients with resectable and unresectable RPS. Our findings suggest that eribulin should be considered a treatment option for unresectable RPS in clinical practice.