Abstract B43: A preponderance of post-menopausal HER2+ breast cancer in the Vietnamese population

Abstract

Abstract Background: Though breast cancer is the most commonly diagnosed cancer and the leading cause of cancer death in women worldwide, relatively little is understood about the differences in prevalence and biology between various populations. For example, breast cancer is far less common in Asia than in North America, and the biology of breast cancer is likely different between these groups as well. There is some limited data to suggest that Asian breast cancer patients may have 35-40% rate of HER2+ breast cancer [1,2], as compared to 15-23% within the general American population [3,4]. Methods: To further examine this possibility, we reviewed our data at the Harris Health Systems' Smith Clinic in Houston, Texas from September 2010 through September 2014 to further characterize the Vietnamese breast cancer patients seen during that time. Using Fisher's Exact Test, we compared our subset of Vietnamese breast cancer patients with the publicly available SEER data from 2010[4]. Results: Among the Vietnamese patients from the Smith Clinic, we found that out of 33 patients with invasive breast cancer, 15 (45%) had HER2+ breast cancer. Interestingly, 64% of the HER2+ cohort was post-menopausal, and 50% of the post-menopausal women had HER2+ breast cancer. Compared with the 2010 SEER data that encompasses 28% of all US breast cancer patients diagnosed that year, regardless of race, the Smith Clinic Vietnamese cohort had a statistically significant higher rate of HER2+ breast cancer, with an odds ratio of 4.7 (45% vs. 15%, p <0.001). Among the women greater than 50 years old in both groups, the Vietnamese women had a higher rate of HER2+ breast cancer than the same age group in the SEER data group (odds ratio 7.0, p <0.001). Conclusion: The patterns observed in this small Vietnamese cohort, and others, do not mirror those seen in the general, multi-racial American breast cancer population. The rate of HER2+ breast cancer in the Smith Clinic Vietnamese group is twice that of the general American population. Other, larger studies have supported the findings of this small group, including a 242-patient study in Vietnam which demonstrated a 41% rate of HER2+ breast cancer; 55% of post-menopausal women had HER2 mutated tumors in this group [1]. Generally, other studies have associated older age and post-menopausal status with a lower rate of HER2+ breast cancer [5,6], but the opposite is true in these Vietnamese women. This unique pattern of breast cancer in Vietnamese women may suggest an underlying genetic or environmental driver, similar to the higher rate of triple negative breast cancer in BRCA1 carriers, or HER2+ breast cancer in women with p53 mutations. We plan to conduct further epidemiologic and genetic research in a larger cohort of Vietnamese breast cancer patients to determine whether an underlying germline genetic mutation or environmental exposure may explain this unusual pattern of breast cancer.