Background: Inflammatory breast carcinoma (IBC) appears to be a clinicopathologic entity distinct from noninflammatory locally advanced breast cancer (LABC). We examined incidence and survival trends for IBC in Surveillance, Epidemiology, and End Results (SEER) Program data with a case definition designed to capture many of its unique clinical and pathologic characteristics.
Methods: We analyzed breast cancer cases diagnosed in the SEER 9 Registries (n = 180,224), between 1988 and 2000. Breast cancer cases were categorized using SEER's "Extent of Disease" codes in combination with International Classification of Diseases for Oncology morphology code 8530/3 and classified as IBC (n = 3648), LABC (n = 3636), and non-T4 breast cancer (n = 172,940). We compared changes in incidence rates over 3-year intervals by breast cancer subtype and race using SEER*Stat. Survival differences by breast cancer subtype and race were assessed using Kaplan-Meier curves and log-rank statistics. All statistical tests were two-sided.
Results: Between 1988 and 1990 and 1997 and 1999, IBC incidence rates (per 100,000 woman-years) increased from 2.0 to 2.5 (P < .001), whereas those for LABC declined (2.5 to 2.0, P = .0025), as did those for non-T4 breast cancer (108 to 101, P = .0084). IBC incidence rates were statistically significantly higher in black women (3.1) than in white women (2.2) during the study period (P < .001). Women diagnosed with IBC had statistically significantly poorer survival than women with either LABC or non-T4 breast cancer (log-rank test, P < .001). Median survival of women with IBC (2.9 years) was statistically significantly shorter than that of women with LABC (6.4 years; P < .0001) or non-T4 breast cancer (> 10 years, P < .0001). Black women with IBC or LABC had poorer survival than white women with IBC or LABC, respectively (log-rank test, P < .001).
Conclusions: Throughout the 1990s, IBC incidence rose, and survival improved modestly. Substantial racial differences were noted in age at diagnosis, age-specific incidence rates, and survival outcomes.