Variability in treatment approaches, outcomes, and recurrence patterns after curative intent treatment for primary retroperitoneal sarcomas in Latin America: A report on 333 patients from LATAMSARC collaborative working group

Background and objective: Retroperitoneal sarcomas (RPS) are rare tumors with several well-defined histologic subtypes.This study aimed to assess the epidemiology, treatment patterns, and outcomes of patients with retroperitoneal sarcoma in Latin America and analyze patterns of recurrence and treatment variations in a large population of patients treated at reference centers.Methods: This retrospective descriptive study utilized an electronic database of medical records from LATAM-SARC (a group studying sarcomas consisting of different centers in various countries in Latin America, including Argentina, Chile, Costa Rica, Mexico, and Peru).Adult patients (18 years) with retroperitoneal sarcoma who underwent surgery at six cancer centers in Latin America were included.Key outcomes were practice patterns, overall survival (OS), and progression-free survival (PFS).Results: In this retrospective study, 333 patients diagnosed with retroperitoneal sarcomas met the inclusion/ exclusion criteria.The cohort consisted of 157 females (42.3 %) and 176 males (57.7 %), with an average age of 53.9 years (SD 13.37).Histology most commonly included Dedifferentiated Liposarcoma (31.5 %), Well-Differentiated Liposarcoma (29.7 %), and Leiomyosarcoma (9.9 %).The tumors predominantly resided in the retroperitoneum (81.7 %) and showed a mean diameter of 23.53 cm (SD 13.8 cm).Surgical interventions varied, with Complete Compartmental Resection performed in 31.2 % of cases and Simple Complete Resection in 29.4 %.Postoperative complications were documented, with Clavien-Dindo Grade 3 complications occurring in 16.8 % of patients.An R0/1 resection was obtained in 91.6 % of cases.The ICU admission rate post-surgery was 18.6 %.Adjuvant treatments included radiotherapy in 8.1 %.Local recurrence occurred in 20.7 % of cases, with the majority being ipsilateral.Distal recurrence was observed in 15 patients, predominantly affecting the liver.The mean overall survival was 65.5 months, and disease-free survival was 47.0 months. Conclusion:This study provides information on the epidemiology, treatment patterns, and outcomes of retroperitoneal sarcomas in a group of reference centers in Latin America.These results represent Latin America's largest body of evidence on retroperitoneal sarcomas.