Obesity and Mortality After Breast Cancer by Race/Ethnicity: The California Breast Cancer Survivorship Consortium

Abstract

We investigated body size and survival by race/ethnicity in 11,351 breast cancer patients diagnosed from 1993 to 2007 with follow-up through 2009 by using data from questionnaires and the California Cancer Registry. We calculated hazard ratios and 95% confidence intervals from multivariable Cox proportional hazard model-estimated associations of body size (body mass index (BMI) (weight (kg)/height (m)(2)) and waist-hip ratio (WHR)) with breast cancer-specific and all-cause mortality. Among 2,744 ascertained deaths, 1,445 were related to breast cancer. Being underweight (BMI <18.5) was associated with increased risk of breast cancer mortality compared with being normal weight in non-Latina whites (hazard ratio (HR) = 1.91, 95% confidence interval (CI): 1.14, 3.20), whereas morbid obesity (BMI ≥ 40) was suggestive of increased risk (HR = 1.43, 95% CI: 0.84, 2.43). In Latinas, only the morbidly obese were at high risk of death (HR = 2.26, 95% CI: 1.23, 4.15). No BMI-mortality associations were apparent in African Americans and Asian Americans. High WHR (quartile 4 vs. quartile 1) was associated with breast cancer mortality in Asian Americans (HR = 2.21, 95% CI: 1.21, 4.03; P for trend = 0.01), whereas no associations were found in African Americans, Latinas, or non-Latina whites. For all-cause mortality, even stronger BMI and WHR associations were observed. The impact of obesity and body fat distribution on breast cancer patients' risk of death may vary across racial/ethnic groups.

Energy homeostasis genes and survival after breast cancer diagnosis: the Breast Cancer Health Disparities Study

“…Nonetheless, little evidence has thus far been produced to show an association between GHRL polymorphisms and survival in breast cancer patients. However, GHRL polymorphisms have been associated with obesity (3) and recent studies have associated obesity with decreased survival in breast cancer patients (30, 31), particularly in Hispanics with morbid obesity (18) but these results are far from conclusive and are contradicted by other studies (32). …”

“…We evaluate associations by genetic ancestry, given differences in risk associated with these genes by Native American (NA) ancestry (15). Additionally, NA ancestry has been shown to be an important determinate of breast cancer risk among population of mixed Caucasian and NA ancestry, with women with greater NA ancestry having lower incidence of breast cancer than women of European ancestry (16, 17) We evaluate the modifying effects of body mass index (BMI) on survival given the relationship between these genes and BMI and breast cancer (15, 18-20). …”

The Effect of Patient and Contextual Characteristics on Racial/Ethnic Disparity in Breast Cancer Mortality

“…The variables that were included for each of the four domains of interest were, for contextual factors , measures of total business count, housing crowding, urban/rural categorization, population density, commuting via public transportation, restaurant environment, traffic density, and hospital socioeconomic composition(31, 32); for physical activity , measures of activity between the ages of 10 and 19, between age 10 and diagnosis of breast cancer, and in the ten years prior to diagnosis of breast cancer(33); for body size , pre-diagnosis body mass index (BMI) (34); and for comorbidity , history of hypertension, diabetes, or myocardial infarction(35). Because not all of the CBCSC studies collected data relevant to the four domains of interest, the domain-specific analyses were restricted to sub-cohorts comprising cases from the studies with data relevant to these domains.…”

“…The baseline model variables are listed in Supplemental Table 1 and further details of its development are described in the Supplemental Methods. The CBCSC included four exposure domains: contextual factors(31, 32), physical activity(33),body size(34), and comorbidity(35) to investigate their roles in breast cancer-specific and overall mortality. For this analysis we selected representative variables that were found to be predictive of outcome in these analyses as exposures of interest.…”

“…We have previously reported on the role of institutional and neighborhood contextual factors(31, 32), low physical activity(33), large body size(34), and comorbidities(35) in relation to mortality following breast cancer diagnosis in the large California Breast Cancer Survivorship Consortium (CBCSC) study, which comprised 12,210 invasive breast cancer cases diagnosed between 1993 and 2007(36). Our objective in the present analysis was to investigate the contribution of each of these four domains of risk factors to the apparent racial/ethnic disparity in breast cancer-specific mortality within the context of a single baseline model that included common demographic, clinical, and disease characteristics.…”