Alveolar Soft Part Sarcoma: Progress Toward Improvement in Survival? A Population-Based Study

Background: Alveolar soft part sarcoma (ASPS) is a rare histological subtype of soft-tissue sarcoma, which remains refractory to conventional cytotoxic chemotherapy. We aimed to characterize ASPS and investigate whether the oncological outcome has improved over the past decade.Methods: One hundred and twenty patients with newly diagnosed ASPS from 2006 to 2017 were identified from the Bone and Soft-Tissue Tumor Registry in Japan. The Kaplan–Meier estimate and Cox proportional hazard model were used to investigate the survival outcomes and factors affecting prognosis.Results: The study cohort comprised 34 (28%) patients with localized ASPS and 86 (72%) with metastatic disease at presentation. The 5-year disease-specific survival (DSS) was 68% for all patients and 86% and 62% for localized and metastatic disease, respectively (p = 0.019). Metastasis at presentation was the only adverse prognostic factor for DSS (hazard ratio [HR]: 7.65; p = 0.048). Patients who were >25 years (80%; p = 0.023), had deep-seated tumors (75%; p = 0.002), and tumors >5 cm (5–10 cm, 81%; >10 cm, 81%; p < 0.001) were more likely to have metastases at presentation. In patients with localized ASPS, adjuvant chemotherapy or radiotherapy did not affect survival, and 13 patients (45%) developed distant metastases in the lung (n = 12, 92%) and brain (n = 2, 15%). In patients with metastatic ASPS (lung, n = 85 [99%]; bone, n = 12 [14%]; and brain n = 9 [11%]), surgery for the primary or metastatic site did not affect survival. The use of pazopanib significantly prolonged survival in patients who received systemic treatment (p = 0.045), whereas doxorubicin-based cytotoxic chemotherapy did not. Overall, a trend toward improved DSS for metastatic ASPS has been observed since 2012 (5-year, 58%–65%; p = 0.117), when pazopanib was approved for use in advanced disease.Conclusion: The national study confirmed a unique feature of ASPS with frequent metastasis to the lung and brain but an indolent clinical course. An overall trend toward prolonged survival after the introduction of targeted drugs encourages continuous efforts to develop novel therapeutic options for this therapeutically resistant soft-tissue sarcoma.