Shama Virani, PhD
Nominated From: University of Michigan
Research Site: Thailand
Research Area: HIV/AIDS; Cancer
Primary Mentor: Dr. Laura Rozek
Breast cancer and HIV risk, prevalence, and characterization in Thailand
Breast cancer is a complex disease comprised of several biological subtypes. The etiologic importance of this heterogeneity is underappreciated in Thailand, as prevalence of these subtypes is currently unknown. This is further complicated by the potentially distinct risk factors associated with subtypes of breast cancer. As Thailand continues to develop, environmental and lifestyle factors change to promote an epidemiologic transition, characterized by decreasing rates of mortality due to infectious diseases and increasing rates of chronic conditions, including cancer. There is a shift towards high risk factor profiles for breast cancer, commonly seen in developed regions, across known classical risk factors. However, the increase in breast cancer incidence is not entirely attributable to westernization. Populations in LMICs that don’t exhibit classical risk factors have high rates of breast cancer, indicating that there are population-specific risk factors that contribute to incidence.
Proper identification of high-risk groups for breast cancer in Thailand requires characterization of known, classical risk factors, unknown, population-specific risk factors and prevalence of breast cancer subtypes. A case-control study is ideal for determining risk profiles of breast cancer. However, an inherent limitation for these studies in Thailand is the lack of a population-based control database. Widespread use of case-control studies to address the increasing cancer burden in Thailand necessitates the development of a control ascertainment protocol that can be applied within the national healthcare infrastructure. These studies are critical in determining effective prevention strategies and to generate specific hypotheses for future studies. My long-term goal is to address the growing burden of breast cancer in Thailand through promotion of case-control studies to characterize cancer risk profiles specific to this population. The objective of this proposal is to identify high-risk groups by characterizing classical and novel risk factors of breast cancer, particularly by subtypes. The central hypothesis is that breast cancer incidence rates are increasing in Thailand due to changes in population risk profiles attributable to lifestyle, environment and westernization. The rationale for this proposal is that by determining high-risk groups, targeted primary prevention and screening approaches can be utilized to decrease incidence and mortality in the total population.
Thailand is a rapidly developing lower-middle-income country and thereby adopting western culture, resulting in a shift towards classical risk factors of breast cancer. Although increasing incidence of breast cancer in LMICs has been primarily attributed to westernization, studies have shown that populations with low classical risk factors, such as body mass index, parity, age at first full-term pregnancy, duration of breastfeeding, education, and socioeconomic status, still had high rates of breast cancer. Epidemiologic features of breast cancer appear to be distinct by population compared to western countries. For example, in western countries, women with triple negative breast cancers tend to be younger than those with ER/PR+/HER2- tumors, however, this was not seen in Malay women and the opposite trend was seen in Chinese and Taiwanese women. Preliminary evidence collected by our group shows a higher proportion of ER-/PR- cancers in Muslim compared to Buddhist populations in southern Thailand, highlighting the implication of lifestyle factors associated with religious customs in breast cancer incidence. It is likely that a combination of factors, including westernization and lifestyle factors associated with population-specific parameters, such as region, age and religion, are driving breast cancer incidence trends in southern Thailand.