A Real‐World Analysis of Outcomes in CIC‐Rearranged Sarcomas: A Canadian Sarcoma Research and Clinical Collaboration (CanSaRCC) Study

ABSTRACT Introduction CIC‐rearranged sarcomas (CRS) are rare tumors predominantly affecting young adults. Despite distinct biology, CRS are often treated like Ewing sarcomas with multi‐agent chemotherapy, surgery, and radiotherapy, although the benefits of each remain unclear. We report the impact of treatment on response and survival. Methods This retrospective multicenter study included patients diagnosed with CRS between 2002 and 2023. Demographic, treatment, and outcome data were collected. Event‐free (EFS) and overall survival (OS) were estimated using Kaplan–Meier analysis; risk factors were assessed via log‐rank tests and Cox regression. Treatment response was assessed using RECIST. Results Among 27 patients (median age 21.5 years; range 8–83), 14 (52%) had localized and 12 (44%) metastatic disease (1 unknown). In the localized group, 6 (43%) received chemotherapy (Response: 2 complete, CR; 1 partial, PR; 1 mixed, MR; 1 stable, SD; 1 progressive disease, PD); 5 (36%) died—3 (21%) had received chemotherapy. Among metastatic patients, 10 (83%) received chemotherapy (1 CR, 5 PR, 2 MR, 1 PD); 9 died (one without chemotherapy). Local control was achieved in 12/14 (86%) localized and 7/12 (56%) metastatic patients. Only surgical resection was associated with improved OS (HR 0.13; p < 0.01) and EFS (HR 0.26; p < 0.01), particularly with R0 resection (EFS HR 0.23; p = 0.02). At median follow‐up of 18 months, 2‐year EFS was 56% vs. 8% ( p = 0.02) and OS was 67% vs. 23% ( p = 0.02) for localized vs. metastatic disease. Conclusion Complete resection is critical in CRS. Chemotherapy benefit remains uncertain, underscoring the need for improved local control and novel, biology‐driven therapies.