Metastatic appendicular soft tissue sarcoma: treatment and survival outcomes of 2,553 patients from the SEER database

Introduction: Patients with soft tissue sarcoma (STS) that present with metastasis at diagnosis have a dire prognosis. Within this patient population, we sought to assess: (1) demographic and clinical characteristics, (2) metastatic patterns, (3) treatment strategies, and (4) disease-specific survival (DSS). Materials and Methods: The SEER database was queried to identify patients with histologically confirmed STS of the pelvis or extremity. Univariate and multivariate analysis was performed using the Cox proportional hazards model. Disease-specific survival (DSS) was analyzed using the Kaplan-Meier method. Results: A total of 22,683 patients were retrieved, out of which 2,553 (11.3%) had metastasis at diagnosis. Leiomyosarcoma, undifferentiated pleomorphic sarcoma (UPS), liposarcoma, synovial sarcoma, spindle cell sarcoma, and alveolar rhabdomyosarcoma (A-RMS) were the six most common STS presenting with metastasis. Among patients with metastasis, 53.7% and 33.2% of patients had primary tumors located in the lower limb and pelvis, respectively. Lung was the most common site of metastasis in all subtypes except A-RMS, in which bone metastases and lymph node (LN) predominated (85.2% and 62.1%, respectively). Chemotherapy and radiotherapy were associated with higher DSS (HR = 0.788 and HR = 0.755, respectively). Five-year DSS was below 20% in all tumor histologies. Two-year DSS for patients with synchronous lung and liver metastases was 28%. Conclusion: Although the lung was the most common site of metastasis, metastatic patterns are highly variable depending on tumor histology. Metastatic A-RMS is most commonly presented with regional LN and bone involvement. Disease-specific survival remained poor for patients with metastatic disease at presentation regardless of (neo)-adjuvant radiotherapy or chemotherapy.