Breast Cancer Coverage from Every Angle

Lifetime Smoking and the Risk for Breast Cancer

By: Joshua Swore
Posted: Monday, April 26, 2021

A study published in Cancer Epidemiology, Biomarkers & Prevention adds to the increasing evidence that greater amounts of lifetime smoking may cause the development of both breast and colorectal cancers. “In addition, the positive associations for lifetime amount of smoking and risk of breast cancer were robust in the multivariable models accounting for possible pleiotropic effects of educational attainment, an indicator of socioeconomic status, and age at menarche,” commented Neil Murphy, PhD, of the International Agency for Research on Cancer, Lyon, France, and colleagues.

The research group used Mendelian randomization to understand genetic variants associated with lifetime smoking and the causal relationship between smoking and cancer. A total of 126 variants were identified in samples from lifetime smoking, and 112 variants were identified in those who had ever smoked regularly. These variants were then studied in relation to 122,977 cases of breast and 52,775 cases of colorectal cancers.

The authors reported a genetic predisposition to lifetime smoking was positively associated with risk for breast cancer (odds ratio [OR] = 1.13; 95% confidence interval [CI] = 1.00–1.26; P = .04) and colorectal cancer (OR = 1.21; 95% CI = 1.04–1.40; P = .01). Estrogen receptor–positive and –negative tumors were also reported to have a similar association. Although a positive correlation of lifetime smoking and risk of colorectal cancer was found in men (OR = 1.32; 95% CI = 1.11–1.59; P < .01) but not women (OR = 1.11; 95% CI = 0.90–1.37; P = .34), the evidence for a difference between the sexes was weak (P heterogeneity = .21).

In contrast to lifetime smoking, genetic predisposition to ever having smoked regularly did not seem to have a positive association with the risk of breast cancer (OR = 1.01; 95% CI = 0.90–1.14; P = .85), nor did it appear to have a positive correlation to estrogen receptor–positive or –negative tumors. A similar result was reported for colorectal cancer as well.

Disclosure: The study authors reported no conflicts of interest.

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