Outcomes and Prognostic Factors for a Consecutive Case Series of 115 Patients with Somatic Leiomyosarcoma John A. Abraham, MD, Michael J. Weaver, MD, Jason L. Hornick, MD, PhD, David Zurakowski, PhD, and John E. Ready, MD Investigation performed at Brigham and Women’s Hospital, Boston, Massachusetts Background: Leiomyosarcoma is an uncommon tumor that affects 500 to 1000 patients in the United States annually. The purpose of our study was to further define survival rates as well as to identify multivariable predictors of disease- specific mortality, local recurrence, and development of distant metastasis following surgical resection. Methods: We studied a consecutive series of patients treated for leiomyosarcoma at our institution (a tertiary-care referral center) over a ten-year period. Only patients with leiomyosarcoma of soft tissues, vasculature, or bone were included. Those with uterine, gastrointestinal, or cutaneous forms of the disease were excluded. This yielded a cohort of 115 patients with complete follow-up data on which statistical analysis was performed. Results: One-year, five-year, and ten-year disease-specific survival rates were 87%, 57%, and 19%, respectively. Tumor depth (p < 0.01), histological grade (p < 0.01), and metastasis at presentation (p = 0.03) were found to be multivariable predictors of mortality. Both retroperitoneal location (p = 0.01) and mitotic rate (p < 0.001) were predictive of distant metastasis. Resection margin was the only multivariable significant predictor of local recurrence in the group treated with surgical resection (p < 0.001). Conclusions: Leiomyosarcoma is an aggressive disease, with a generally poor prognosis. Depth of tumor and high histological grade are indicators of a poor prognosis. Retroperitoneal tumors have a particularly high potential to metastasize. Level of Evidence: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence. L eiomyosarcoma is an uncommon tumor associated with a generally poor prognosis. There are approximately 10,000 soft-tissue sarcomas diagnosed within the United States every year. Of these, 5% to 10% (500 to 1000 cases) can be definitively classified as leiomyosarcoma 1-3 . Leiomyosarcoma can be further subclassified into somatic, vascular, and osseous lesions. Cutaneous leiomyosarcoma is generally considered a distinct disease entity with an excellent prognosis relative to other sar- comas, especially when limited to the dermis. Other forms of leiomyosarcoma include gastrointestinal and uterine tumors, but these are thought to represent distinct disease entities with a different prognosis and treatment algorithm compared with so- matic leiomyosarcoma. Histological studies of somatic soft-tissue leiomyosar- comas have shown that many of these lesions directly arise from smooth muscle cells in the walls of blood vessels. The most common site of leiomyosarcoma of soft tissue is the retroperitoneum, accounting for approximately 50% of all cases; however, leiomyosarcoma can affect almost any part of the body including the extremities, trunk, blood vessels, heart, and bones 1 . Soft-tissue leiomyosarcomas were at one time thought to arise from leiomyomas, but current molecular studies suggest this is unlikely 4 . There are no known specific agents that cause leiomyo- sarcoma. Radiation is known to induce sarcomas, but leiomyo- sarcoma rarely has histological findings that can be associated Disclosure: One or more of the authors received payments or services, either directly or indirectly (i.e., via his or her institution), from a third party in support of an aspect of this work. In addition, one or more of the authors, or his or her institution, has had a financial relationship, in the thirty-six months prior to submission of this work, with an entity in the biomedical arena that could be perceived to influence or have the potential to influence what is written in this work. No author has had any other relationships, or has engaged in any other activities, that could be perceived to influence or have the potential to influence what is written in this work. The complete Disclosures of Potential Conflicts of Interest submitted by authors are always provided with the online version of the article. 736 COPYRIGHT Ó 2012 BY THE J OURNAL OF BONE AND J OINT SURGERY,I NCORPORATED J Bone Joint Surg Am. 2012;94:736-44 d http://dx.doi.org/10.2106/JBJS.K.00460