Diagnosis, Prognosis, and Treatment of Alveolar Soft-Part Sarcoma: A Review.

Importance: Alveolar soft-part sarcoma (ASPS) is a rare, translocation-driven sarcoma of the soft tissues. Alveolar soft-part sarcoma often affects young adults and is characterized by indolent behavior but early evidence of metastatic spread. After recognition of ASPS as a specific entity in 1952, retrospective data indicated prolonged survival in patients with metastases, despite inherent resistance to conventional doxorubicin-based chemotherapy. Tyrosine kinase inhibitors and immune checkpoint inhibitors have provided unexpected new treatment strategies for ASPS. Observations: This review includes articles published between 1952 and March 1, 2018. With the introduction of new molecular diagnostic tools and therapies, the distinctive features of ASPS have become more evident. The identification and better understanding of molecular pathways activated by the characteristic t(X;17)(p11;q25) translocation and its correspondent chimeric ASPSCR1-transcription factor E3 (TFE3) fusion protein open new paths to drug development. The associations of TFE3 and facilitation of an immunosuppressive microenvironment provide a rationale for exploring treatments that affect the balance between T-effector cells and T-regulatory cells. Tyrosine kinase inhibitors, such as sunitinib, cediranib, and pazopanib, show activity with either tumor responses or disease stabilization in more than 50% of the cases. Given the association of new agents with patient outcomes, it is too early to say whether metastatic ASPS should still be considered incurable in all patients. Conclusions and Relevance: The biologic outcomes of the canonical genomic event in ASPS remain under investigation; a better understanding of the tumor microenvironment and the multiple pathways activated in this sarcoma, including unusual bioenergetics, MET signaling, and angiogenesis, should lead to more rational therapy. Basket trials and related prospective studies focusing on the intersection of specific signaling pathways and diseases with unique genomic features, such as ASPS, will provide an understanding of new options for care.