(P 370) CLINICAL OUTCOMES OF CUTANEOUS UNDIFFERENTIATED PLEOMORPHIC SARCOMA AND SUBCUTANEOUS MYXOFIBROSARCOMA: A RETROSPECTIVE REVIEW

Objective: Cutaneous undifferentiated pleomorphic sarcoma (UPS) and subcutaneous myxofibrosarcoma are rare soft tissue sarcomas with ill-defined clinical trajectory presenting challenges in treatment given limited prospective data to guide management. We reviewed the clinical course of patients with cutaneous UPS and myxofibrosarcoma at a single academic institution with a focus on patterns of metastasis and treatment outcomes in those who received immunotherapy.

Methods: We conducted a retrospective chart review of 117 patients diagnosed with cutaneous UPS or subcutaneous myxofibrosarcoma. Inclusion criteria were histologically confirmed diagnosis and available clinical follow-up. Demographic, pathologic, and treatment data were collected, including the use of immunotherapy. Clinical outcomes of interest included distant metastasis and survival. Patients were followed from date of diagnosis to last known follow-up or death.

Results: A total of 111 patients were included in the analysis: 32 with UPS and 79 with myxofibrosarcoma. The average age at diagnosis was 68.5 years for cutaneous UPS and 69.8 years for myxofibrosarcoma. Distant metastases occurred in 6 of 32 patients (18.8%) with UPS and 4 of 79 patients (5.1%) with myxofibrosarcoma. Among patients with metastatic disease, progression-free survival (PFS) for cutaneous UPS was three months. For metastatic myxofibrosarcoma, PFS was four months. A total of 14 patients in the cohort received immunotherapy, seven in each group. The median PFS for patients who received immunotherapy was over four months. Overall, mortality was low in both groups: eight patients with cutaneous UPS (25%) and 21 with myxofibrosarcoma (26.5%) died.

Conclusion: In this retrospective cohort study, both cutaneous UPS and subcutaneous myxofibrosarcoma showcased relatively low rates of distant metastases and mortality. However, cutaneous UPS may be somewhat different from subcutaneous myxofibrosarcoma given the increased risk of metastasis in its cohort. Although a small cohort, patients who received immunotherapy had evidence of a durable response. These findings highlight the need for further study of systemic treatment strategies in rare cutaneous and subcutaneous soft tissue sarcomas.