Abstract P3-13-06: Racial Differences in Breast Cancer Biomarkers in the Three Ethnic Groups of Sarawak, Malaysia

Abstract

Abstract Sarawak, Malaysia Introduction The Malaysian state of Sarawak has a mixed ethnic population of Natives, Chinese and Malays. Breast cancer (BC) is the most common cancer. We present preliminary results obtained on a case series of 1034 female BC patients diagnosed between 2001 and 2009, representative of the Sarawak patient population (as discussed in our previous publication: Devi et al. 2007). Methods Tumor markers were assessed using immuno-histochemistry, Her2 2+ and Her2 3+ were confirmed using FISH test. Patients were classified as follow: Luminal A : ER+ PR+ and Fish — Luminal B : ER+, PR+ and Fish + Her2-overexpressing : ER-, PR-and Fish — Triple-negative : ER-, PR-and Fish - Chi2 comparisons and multivariate logistic regressions were performed using SAS statistical software. The OR presented are adjusted on age and ethnic groups. Results BC incidence was higher among Chinese (ASR=30.6) than among Malay (ASR=21.2) or Natives (ASR=7.8). In our series, luminal B, Her2-overexpressing and triple negative subtypes were represented in respectively 12%, 11% and 29% of the patients. The triple negative subtype was more frequent among Natives cases (37%) or Malay cases (33%), significantly higher than among Chinese cases (23%). Compared to luminal A, triple negative patients were more likely to be Malay (OR = 2.07; 95%CI= [1.44-2.98]) or Natives (OR = 2.13; 95%CI= [1.48-3.04]), to have older age at menopause (OR for menopause >50 years = 1.59 ; 95%CI= [1.01-2.51]) and less likely to have familial history of BC (OR = 0.52; 95%CI= [0.3260.82]) or to have breast fed for 0 to 6 months (OR = 0.60 ; 95%CI= [0.37-0.97]). Malay and Native triple negative patients were more likely to be overweight when pre-menopausal (OR for BMI 25-29 vs. BMI<25 = 2.02; 95%CI=[1.02-3.97]), such a trend did not exist in Chinese patients. Compared to luminal A, Her2-overexpressing patients were more likely to be Malay (OR = 1.66; 95%CI= [1.01-2.70]) and to have children (OR parous vs nulliparous=1.99; 95%CI= [1.11-3.59]). The number of children did not influence the association. A borderline significant association (p=0.053) was observed with menopausal status Compared to luminal A, luminal B, were significantly more likely to be Malay (OR=2.10; 95%CI= [1.32-3.33]), to be premenopausal (OR=1.87; 95%CI=[1.13-3.10]) and to be over-weight (OR for BMI 25-29 vs. BMI<25 = 1.64; 95%CI=[1.06-2.53]) especially when premenopausal (OR=1.96; 95%CI= [1.05-3.65]). Surprisingly, age distribution did not differ between Luminal A, B, Her2- overexpressing and triple-negative patients, however 80% of our patients were <60. Conclusions The proportion of triple negative patients in our series revealed to be one of the highest ever reported, and was significantly higher than in Caucasian or other Asian cases series. Our results confirm the finding the HER2- overexpression is more frequent in Asians compared to whites or African American. Regarding risk factors our results did not conflict with those reported in the literature for Caucasian populations however some specific patterns were observed that need to be studied further. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-13-06.