Trends in Endometrial Cancer Incidence Rates in the United States, 1999–2006

BACKGROUND: Risk factors for endometrial cancer, such as hormone replacement therapy (HRT) and obesity, have changed significantly in the last decade. We investigated trends in endometrial cancer histologic subtypes on a national level during 1999-2006. METHODS: Data covering 88% of the U.S. population were from central cancer registries in the National Program of Cancer Registries (NPCR) and Surveillance, Epidemiology, and End Results (SEER) programs that met high-quality United States Cancer Statistics (USCS) criteria. Our analyses included females with microscopically confirmed invasive uterine cancer (n=257,039). Age-adjusted incidence rates and trends for all invasive uterine cancers and by endometrial cancer histologic subtypes (type I and II) were assessed. RESULTS: There were 145,922 cases of type I endometrial cancers and 15,591 cases of type II for 1999-2006. We found that type I endometrial cancers have been increasing, whereas type II endometrial cancers and all invasive uterine cancers have been relatively stable throughout the 1999-2006 period. CONCLUSIONS: During the past decade, the overall burden of uterine cancer has been stable, although there have been changes in underlying histologies (e.g., endometrial). Changes in trends for underlying histologies may be masked when reviewing trends irrespective of histologic subtypes. Our findings suggest the need to examine trends of uterine cancer by histologic subtype in order to better understand the burden of endometrial cancer in relation to these subtypes to help women at increased risk for developing more aggressive types of endometrial cancer (e.g., type II).