P4-20-05: Inflammatory Breast Cancer: Comparison of Epidemiology, Biology, and Prognosis between Japan and the United States, a Hospital-Based Study.

Abstract

Abstract Background: Inflammatory breast cancer (IBC) is a challenging disease characterized by low incidence, rapid progression, and poor survival. The epidemiology of IBC has been slow to emerge, given that the rarity of IBC makes large prospective clinical trials difficult. Compared to non-IBC, well-established features of IBC include a younger age of onset and lower frequency of hormone receptor positivity. Higher body mass index (BMI) is a purported risk factor. Previous reports also suggest that IBC is associated with more racial disparities, including incidence and age at diagnosis. The epidemiology of IBC in East Asia, however, has not been investigated. We performed a comparative study of IBC in Japan versus the United States to determine its epidemiologic and clinical features and to evaluate the differences in epidemiological factors between the two countries. Patients and Method: Patients who visited St. Luke's International hospital (SLIH) in Tokyo, Japan and The University of Texas MD Anderson Cancer Center (MDA) in Texas, USA between 2003 and 2009 were identified. Epidemiological and biological data were collected from electronic medical records. Patient and tumor characteristics were tabulated and stratified by hospital. Kaplan-Meier curves were created for survival estimates and log-rank test was used for cross-group comparisons. Cox proportional-hazard analysis was used to identify a subset of significant prognostic variables that related to overall survival. Result: 34 patients at SLIH and 531 patients at MDA were identified. Mean age at diagnosis was 52 years old (range, 32–81, SD, 10.8) and 50 years old (range, 22–87, SD, 11.6), respectively (P=0.476). Mean BMI was 22.9 kg/m2 (range, 17.3−30.5, SD 3.3 ) and 31.0 kg/m2 (range, 13.6−88.9, SD, 7.8) respectively (P<0.01). Clinical Staging was not significantly different; Stage IIIB 38.2%, Stage IIIC 26.5%, and Stage IV 32.4% at SLIH versus 48.6%, 23.7%, and 27.3% at MDA (P= 0.167). Estrogen receptor (ER) and progesterone receptor (PR) negative cases were, respectively, 50.0% and 64.7% at SLIH and 50.5% and 64.2% at MDA (ER, P= 0.935; PR, P=0.908). Her-2 over-expression cases were 38.2% at SLIH and 28.6% at MDA (P=0.174). A significant difference in nuclear grade was seen between SLIH and MDA: 20.6% at SLIH were Grade 3 versus 68.7% at MDA (P<0.01). Median overall survival at SLIH was 3.6 years versus 2.3 years at MDA (P=0.570). No prognostic factors were associated with overall survival. Conclusion: Though IBC at SLIH differed significantly from IBC at MDA by several epidemiologic and biologic factors, there was no significant difference in survival. To define the epidemiological, prognostic, and risk factors of IBC in Japan, as well as in the world, further studies are needed. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-20-05.