Risk Factors and Breast Cancer Survival in Black/White Women

Institution: Beckman Research Institute of the City of Hope
Investigator(s): Yani  Lu , M.D. -
Award Cycle: 2009 (Cycle 15) Grant #: 15FB-0004 Award: $89,996
Award Type: Postdoctoral Fellowship
Research Priorities
Disparities>Disparities: eliminating the unequal burden of breast cancer



Initial Award Abstract (2009)

Eliminating racial disparities in cancer mortality by the year 2015 is an American Cancer Society challenge goal. To date, the disparity in breast cancer mortality between black women and white women is still increasing with black women having the highest mortality rates. The reasons for this racial disparity are not completely understood. Risk factors for breast cancer incidence may promote the development of specific types of breast cancer, and thus influence the course of disease and have an effect on survival. Although data on relationship between risk factors and breast cancer survival are increasing, few studies provide detailed information on multiple risk factors and few data on these relationships exist for black women.

In this project, we will use the unique opportunity provided by the Women’s Contraceptive and Reproductive Experiences (CARE) Study to investigate the association between established breast cancer risk factors and their effect on all-cause mortality and breast cancer-specific mortality. We will also examine whether these risk factors explain at least, in part, the racial disparity in breast cancer survival between black women and white women. Our aims to determine whether breast cancer survival is affected by a woman’s:
1) family history of breast cancer
2) body size measures including height, weight, body mass index (kg/m2, BMI), and weight change before diagnosis
3) recreational physical activity before diagnosis
4) reproductive characteristics including age at menarche, parity, age at first full-term pregnancy, and time since most recent birth and breastfeeding
5) use of exogenous hormones (oral contraceptives and menopausal hormone therapy)

For this study we will use participants in the Women’s CARE Study, which enrolled 2953 white and 1622 black invasive breast cancer patients aged 35 to 64 years, have been followed for survival since their diagnoses between 1994 and 1998. Since completing a detailed interview on breast cancer risk factors shortly after diagnosis, 1044 (511 black and 533 white) have died with 793 deaths (394 black and 399 white) attributed to breast cancer.

Identifying lifestyle and other factors that modify the risk of mortality following breast cancer will enhance our ability to improve the survival experience of women diagnosed with breast cancer. It will help us predict whether specific subgroups have an increased risk of mortality. It will also provide leads to understanding the underlying biology mechanisms influencing prognosis, and thus will provide potential solutions for clinical decision for breast cancer patients.




Progress Report 1 (2010)

Many lifestyle and environmental factors that are associated with breast cancer incidence risk may also influence tumor progression and affect survival after breast cancer diagnosis. Although breast cancer-specific mortality rates have decreased for both black women and white women, the mortality rates decreased less among black women than among white women and the survival disparity remain sizable. In this proposal, we proposed to investigate the extent to which established breast cancer risk factors may be associated with breast cancer survival in a cohort of black women and white women with invasive breast cancer who were enrolled in a population-based case-control study.

The goals for the first year of the current grant were to merge the Women’s CARE Study database with the follow-up survival data from each of the 5 centers (Atlanta, Detroit, Philadelphia, Los Angeles, and Seattle); clean the outcome variables, and investigate whether family history of breast cancer, body size including height, weight, body mass index (kg/m2), and weight change before diagnosis affects breast cancer survival; furthermore, whether these factors explain the poorer survival of black women.

Women with family history of breast cancer had a similar risk of mortality compared with women without family history. The prevalence of obesity (body mass index =30 kg/m2) at 5-year before breast cancer diagnosis was higher among black women (26.9%) than white women (12.1%). Obese women were more likely to be older, with low education level, postmenopausal women, with more comorbid conditions, or diagnosed of non-localized tumors. Compared to women with normal weight (body mass index 20-24.9 kg/m2), those who were obese had a greater risk of all-cause mortality and breast cancer-specific mortality. By race, however, the associations with all-cause mortality and breast cancer-specific mortality were observed among white women, but not among black women, regardless of estrogen receptor status. These results suggest that obesity plays an important role in mortality among white but not among black breast cancer patients. Thus, it is unlikely that different distribution of obesity among black women and white women diagnosed with breast cancer account for the poorer survival of black women.

Our plan in next year is to investigate whether other breast cancer risk factors (e.g. reproductive factors, exogenous hormone use, smoking and alcohol, etc.) have associations with mortality, and whether these factors explain the racial disparity in survival.