Changing incidence rate of invasive lobular breast carcinoma among older women

BACKGROUND. In 1998, an unusually large number of invasive lobular breast c arcinoma cases were seen at the University of Washington. The purpose of th is study was to assess whether the incidence rate of invasive lobular carci noma has been increasing disproportionately compared with the incidence rat e of invasive ductal carcinoma. METHODS, Age specific and age-adjusted breast carcinoma incidence rates fro m 1977-1995 were obtained from the nine population-based cancer registries that participate in the Surveillance, Epidemiology, and End Results (SEER) program. Three histologic groupings were used: lobular, ductal, and all inv asive breast carcinomas. Overall incidence rates for each grouping, as well as for each stage (local, regional, and distant), were obtained. RESULTS. The rate of incidence of lobular carcinoma increased steadily from 1977-1995 in women age greater than or equal to 50 years whereas it remain ed stable in women age < 50 years. Alternatively, the rate of incidence of ductal carcinoma increased steadily from 1977-1987, but from 1987-1995 it r emained relatively constant across all age groups. CONCLUSIONS. The incidence rates of invasive lobular breast carcinomas incr eased steadily since 1977 whereas the incidence rates of invasive ductal ca rcinoma have plateaued since 1987. This rise occurred specifically among wo men age greater than or equal to 50 years and may be related to postmenopau sal status. Further epidemiologic, clinical, and laboratory research is req uired to assess what factors are contributing to this trend. (C) 2000 Ameri can Cancer Society.