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

AIM: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.