Alcohol, smoking, and risks of breast cancer recurrence and mortality among women with luminal, triple-negative, and HER2-overexpressing breast cancer.

BACKGROUND: This study evaluates the relationship between smoking, alcohol, and breast cancer outcomes according to molecular subtype.

METHODS: This population-based prospective cohort consisted of 3,876 women aged 20-69 diagnosed with a first primary invasive breast cancer from 2004 through 2015 in the Seattle-Puget Sound region. Breast cancer was categorized into three subtypes based on estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) expression: luminal (ER+), triple-negative (TN) (ER-/PR-/HER2-), and HER2-overexpressing (H2E) (ER-/HER2+). We fit Cox proportional hazards models to assess the association between alcohol consumption and smoking status at diagnosis and risks of recurrence, breast cancer-specific mortality, and all-cause mortality.

RESULTS: Histories of ever smoking (HR:1.33; 95%CI:1.01-1.74) and current smoking (HR:1.59; 95%CI:1.07-2.35) were associated with greater risk of breast cancer recurrence among TN cases. Smoking was also associated with greater risk of recurrence to bone among all cases and among luminal cases. Elevated risks of breast cancer-specific and all-cause mortality were observed among current smokers across all subtypes. Alcohol use was not positively associated with risk of recurrence or mortality overall; however, TN patients who drank four or more drinks per week had a decreased risk of recurrence (HR:0.71; 95%CI:0.51-0.98) and breast cancer-specific mortality (HR:0.73; 95%CI:0.55-0.97) compared to non-current drinkers.

CONCLUSIONS: Breast cancer patients with a history of smoking at diagnosis have elevated risks of recurrence and mortality.

IMPACT: These findings underscore the need to prioritize smoking cessation among women diagnosed with breast cancer.