High relapse rates and poor survival of native Hawaiian (NH) women with HER2-positive breast cancer.

Abstract

e11116 Background: The Hawaii Tumor Registry reports of higher mortality rates and advanced disease at diagnosis for Native Hawaiian (NH) women with breast cancer may represent a biologically more aggressive cancer complimented by HER2 overexpression. This study investigates the association of HER2 overexpression potentiating NH breast cancer leading to early relapses and poor survival. Methods: This retrospective study analyzed data for women diagnosed with breast cancer from 2000-2005, and followed through 2007 (n=1488), at the Queen’s Medical Center in Honolulu, Hawaii. This study focused on three major ethnicities: NH (n=359), Japanese (JA; n=609) and Caucasian (CA; n=520) women. Demographics on tumor grade, stage, ER, PR, and HER2 expression were obtained from the hospital’s cancer registry. Cox regression models of 1) relapse; 2) death for these patients were used to evaluate the association of intrinsic breast cancer subtypes and ethnicities. Survival time was the interval between diagnosis and death or cessation of follow-up at 2007. Results: We compared the frequency distribution of tumor subtypes (Luminal A, Luminal B, HER2-positive, and Triple Negative). Triple Negative breast cancers were associated with increased risk of death for the NH women (Hazard Ratio (HR)=2.8, p=0.046) and JA (HR=2.2, p=0.052). HER2-positive breast cancers were associated with increased risk of death for NH (HR=2.6, p=0.044) and CA (HR=2.9, p= 0.018) women, but not for the JA women. In HER2+ tumors, we observed that there was a significant increase in the frequency of relapse for NH (23.6%) compared to JA (9.8%) or CA (10%) women. Cox regression analysis indicate that NH women are more likely to relapse (HR=3.28) compared to JA (HR=1.05) or CA (HR=1.2) women. Conclusions: These data illustrate the importance of cross-ethnic studies in understanding racial/ethnic based differences in breast cancer incidence and mortality. We observed that Her2 overexpression is associated with disproportionately higher relapse and mortality rates in NH women with breast cancer. An ethnicity - HER2 interaction is suggested by this data and further molecular studies are indicated.