The Impact of Smoking and Alcohol on Breast Cancer Risk

Breast cancer is the most frequently diagnosed cancer and the primary cause of cancer-related death among women worldwide.¹ In honor of Breast Cancer Awareness Month, which is observed annually in October, this article examines how smoking and alcohol consumption contribute to breast cancer development.

Smoking and Breast Cancer Risk

Historically, data on the impact of tobacco smoking on breast cancer risk were inconsistent, and therefore, firm conclusions about the relationship between smoking and breast cancer risk could not be drawn.² However, recent systematic reviews and meta-analyses suggest that smoking is a risk factor for breast cancer; these studies found that both current and former smokers had significantly increased incidence of breast cancer, compared to never smokers. Breast cancer risk increased with greater number of cigarettes smoked per day and with longer duration of smoking.^3,4 

Impact on outcomes. Various studies have shown that smoking affects survival among patients with breast cancer. Research strongly suggests that smoking increases the risk of all-cause mortality among patients with breast cancer, particularly among those currently smoking at cancer diagnosis and those with a greater smoking intensity, duration, or pack-year exposure.^5–12 Considering breast cancer–specific mortality (BCSM), research indicates that patients who continue to smoke postdiagnosis have an increased risk of BCSM compared to never smokers,^5–7,11,12 whereas former smokers (those who quit >1 year before breast cancer diagnosis) do not have an elevated risk of BCSM compared to never smokers.^6,7,9 Current smokers might also face an elevated risk of recurrence.⁵

Alcohol consumption and Breast Cancer Risk

The International Agency for Research on Cancer has identified a causal relationship between alcohol consumption and female breast cancer,¹³ and research from the World Cancer Research Fund and American Institute for Cancer Research suggests that alcohol convincingly increases the risk of postmenopausal breast cancer, and that there is a probable increase in the risk of premenopausal breast cancer.¹⁴ A Lancet Oncology study¹⁵ found that, globally, female breast cancer was one of the most common alcohol-related cancers, with an estimated 98,300 cases attributable to alcohol consumption in 2020. Research suggests that breast cancer risk increases with any level of alcohol consumption, though greater consumption is linked to greater risk.^16–18  

Impact on outcomes. Research indicates that there is not a significant association between mortality (including all-cause mortality and BCSM) and alcohol consumption (including pre- and postdiagnosis consumption).^{11,12,19–22} Some studies have shown a protective effect of varying levels of alcohol consumption on mortality outcomes,^11,22,23 but these findings should be interpreted with caution.

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