Abstract LB-442: The association of HER2/neu overexpression with relapse and poor survival in Native Hawaiian women with breast cancer

Abstract

Abstract Cross-ethnic comparisons of data from the Hawai'i SEER Cancer Registry show that Native Hawaiian female breast cancer patients have the highest incidence and mortality among all ethnic populations in Hawai'i and Japanese had the lowest mortality. Factors that contribute to this disparity include socioeconomic status, access to healthcare, stage at diagnosis, and tumor biology. Breast cancer is a heterogeneous disease, with multiple subtypes based on histologic type, estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2/neu) expression profiles. This single institution-based retrospective study analyzed data for female patients diagnosed with breast cancer from 2000–2005 and followed through 2007 (n=1488) at the Queen's Medical Center in Honolulu, Hawai'i. This study focused on three major ethnic populations in Hawai'i: Native Hawaiian (n=359), Japanese (n=609) and Caucasian (n=520) women. Information on tumor stage, ER, PR, and HER2/neu expression were obtained from the hospital's cancer registry. Cox regression models of 1) relapse 2) death for breast cancer patients were used to evaluate the association with tumor subtype and ethnicity, adjusting for stage. Survival time was defined as the interval between diagnosis and the endpoint or cessation of follow-up at 2007. We compared the frequency distribution of intrinsic breast cancer subtypes [Luminal A (ER/PR+; HER2/neu−), Luminal B (ER/PR+; HER2/neu+), HER2/neu-positive (ER/PR−, HER2/neu+), and Triple Negative (ER/PR−, HER2/neu−)]. Native Hawaiian women had the lowest prevalence of Lum A subtype (69%) compared to Japanese (76%) and Caucasian women (72%). Native Hawaiian women had a higher prevalence of Lum B (14%) compared to Japanese (6%) and Caucasian (12%) women. Prevalence of Triple Negative and HER2/neu subtypes was similar for the three ethnic groups. There was a difference in survival associated with the intrinsic subtypes for the three ethnic groups. Triple Negative breast cancers were associated with increased risk of death for the Native Hawaiian (HR=2.8, p=0.046) and Japanese (Hazard Ratio (HR)=2.2, p=0.052) women. The HER2/neu-positive subtype was associated with increased risk of death for Native Hawaiian (HR=2.6, p=0.044) and Caucasian (HR = 2.9, p = 0.018) women, but not for the Japanese women. When we examined the outcome of relapse associated with HER2/neu overexpression, we observed Native Hawaiian (HR=3.28) women were more likely to relapse compared to Japanese (HR=1.05) or Caucasian (HR=1.2) women. We identified an association between differences in the prevalence of intrinsic subtypes, relapse and survival levels, and racial/ethnic background. These data illustrate the importance of cross-ethnic studies to increase our understanding of racial/ethnic based differences in breast cancer incidence and mortality in order to reduce disparities. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-442. doi:10.1158/1538-7445.AM2011-LB-442