Modifiable risk factors in women at high risk of breast cancer: a systematic review

Abstract

Background: Modifiable risk factors (alcohol, smoking, obesity, hormone use, and physical activity) affect a woman's breast cancer (BC) risk. Whether these factors affect BC risk in women with inherited risk (family history, BRCA1/2 mutations, or familial cancer syndrome) remains unclear.

Methods: This review included studies on modifiable risk factors for BC in women with inherited risk. Pre-determined eligibility criteria were used and relevant data were extracted.

Results: The literature search resulted in 93 eligible studies. For women with family history, most studies indicated that modifiable risk factors had no association with BC and some indicated decreased (physical activity) or increased risk (hormonal contraception (HC)/menopausal hormone therapy (MHT), smoking, alcohol). For women with BRCA mutations, most studies reported no association between modifiable risk factors and BC; however, some observed increased (smoking, MHT/HC, body mass index (BMI)/weight) and decreased risk (alcohol, smoking, MHT/HC, BMI/weight, physical activity). However, measurements varied widely among studies, sample sizes were often small, and a limited number of studies existed.

Conclusions: An increasing number of women will recognize their underlying inherited BC risk and seek to modify that risk. Due to heterogeneity and limited power of existing studies, further studies are needed to better understand how modifiable risk factors influence BC risk in women with inherited risk.

Fig. 1

Systematic review chart

Fig. 2

Alcohol and breast cancer risk in women with BRCA mutations (n = 6) and family history (n = 9). Each bar is divided based on the proportion of included studies that demonstrated an increased risk, decreased risk, or no association with risk of breast cancer due to the specified alcohol exposure. Within each alcohol exposure, each study is represented only once. However, because the category “all alcohol behaviors” combines the results of all other exposure categories, studies may be represented more than once, if the results differ by exposure (e.g., decreased risk with current and no association with total/lifetime alcohol consumption). Numbers on the “all alcohol behaviors” bars indicate the range of risk estimates from studies when reported as a ratio measure (OR/RR/HR). Results from studies reporting only p values or other measures that did not indicate magnitude of effect are not included in these ranges. A Each bar in the figure represents all of the included studies (n = total number of studies) that reported results on the specified alcohol exposure in women with BRCA mutations, separated by BRCA mutation, if provided. Of the studies assessing alcohol type, one looked at wine drinking and the other did not specify the type of alcohol assessed. Please see Tables 1 and 2 for all studies cited. B Each bar in the figure represents all of the included studies (n = total number of studies) that reported results on the specified alcohol exposure in women with family history. Please see Additional file 4: Tables S1 and Additional file 5: Table S2 for all studies cited

Fig. 3

Smoking and breast cancer risk in women with BRCA mutations (n = 9) and family history (n = 9). Each bar is divided based on the proportion of included studies that demonstrated an increased risk, decreased risk, or no association with risk of breast cancer due to the specified smoking exposure. Within each smoking exposure, each study is represented only once. However, because the category “all smoking behaviors” combines the results of all other exposure categories, studies may be represented more than once, if the results differ by exposure (e.g., increased risk with current smoking and no association with past smoking). Numbers on the “all smoking behaviors” bars indicate the range of risk estimates from studies when reported as a ratio measure (OR/RR/HR). Results from studies reporting only p values or other measures that did not indicate magnitude of effect are not included in these ranges. A Each bar in the figure represents all of the included studies (n = total number of studies) that reported results on the specified smoking exposure in women with BRCA mutations, separated by BRCA mutation, if provided. Please see Tables 1 and 2 for all studies cited. B Each bar in the figure represents all of the included studies (n = total number of studies) that reported results on the specified smoking exposure in women with family history. Please see Additional file 4: Table S1 and Additional file 5: Table S2 for all studies cited