Validation of tumor size as staging variable in the revised International Federation of Gynecology and Obstetrics stage I leiomyosarcoma: a population-based study.

INTRODUCTION: Tumor size has been introduced as a staging variable in the 2008 International Federation of Gynecology and Obstetrics (FIGO) staging system for stage I leiomyosarcoma. In the prior 1988 FIGO staging system, leiomyosarcoma used the same staging criteria as endometrial cancer including cervical involvement. In this large population-based study, we validate the use of tumor size for purposes of risk stratification among stage I leiomyosarcoma patients. METHODS: Data were extracted from the Surveillance, Epidemiology, and End Results database between 1988 and 2005. Kaplan-Meier log rank and Cox proportional hazards models were used for survival analysis and to identify possible predictors for survival. RESULTS: The identified cohort included 819 women: 158 (19.3%), 2008 FIGO stage IA and 661 (80.7%), 2008 FIGO stage IB leiomyosarcoma. The 5-year overall survival rate was better in stage IA than in stage IB leiomyosarcoma (76.6% vs 48.4%, P < 0.001). Similarly, the 5-year overall survival rates were significantly different (P < 0.001) among women with different tumor size categories: 5 cm or smaller, 5.1 to 10 cm, and larger than 10 cm (76.6%, 52.9%, and 41.9%, respectively). The difference in 5-year overall survival rates between women with and without cervical involvement was significant (28.5% vs 55.3%, P = 0.014). Although age (P < 0.001), cervical involvement (P = 0.014), tumor grade (P < 0.001), tumor size (P < 0.001), performance of salpingo-oophorectomy (P = 0.001), and stage (P < 0.001) were all significant prognostic factors on univariate analysis, only age (P = 0.007), tumor size (P < 0.001), tumor grade (P < 0.001), and performance of salpingo-oophorectomy (P = 0.02) were significant predictors on multivariate analysis. Variables not found significant on univariate analysis (hence excluded from the Cox model) included lymphadenectomy, radiation, and race. CONCLUSIONS: The new staging system using tumor size is better for risk stratification in stage I leiomyosarcoma compared with the 1988 FIGO staging system of endometrial cancer.