The individual and combined effects of alcohol consumption and cigarette smoking on site-specific cancer risk in a prospective cohort of 26,607 adults 

Scientists examined the individual and synergistic effects of the modifiable lifestyle factors of smoking and drinking on overall and site-specific cancer risk.
Baseline participant data were acquired from Alberta’s Tomorrow Project (ATP). 26,607 Adults 35-69 years old who consented to data linkage and completed relevant questionnaires were included. Incident cases of cancer up to December 2017 were identified via linkage to the Alberta Cancer Registry. Associations between alcohol consumption, cigarette smoking, and cancer risk were examined using adjusted Cox proportional hazard models. Non-linear effects were estimated using restricted cubic splines.
A total of 2,370 participants developed cancer during the study follow-up period. The study found no statistically significant associations between alcohol consumption and incidence of all cancers among males (hazard ratio [HR] 1.14, 95% confidence interval [CI] 0.93-1.40) and females ([HR] 0.89, 95% confidence interval [CI] 0.73-1.10).
Smokers were at an increased risk of developing all cancers (female current smokers: [HR] 1.72, 95% [CI] 1.49-1.99, male current smokers: [HR] 1.24, 95% [CI]
1.03-1.49) with the strongest association observed between current smokers and lung cancer (males: [HR] 11.33, 95% [CI] 4.70-27.30, females: [HR] 23.51,
95% [CI] 12.70-43.60). A 3-way interaction model showed an additive effect between alcohol as a continuous variable (g/day) and pack-years (PYs) consumed for all, colon, and prostate cancers. A “U-shaped” multiplicative interaction was observed for breast cancer (p = 0.05).
The research concludes that alcohol consumption was not statistically associated with cancer risk. Cigarette smoking clearly increased all-cancer risk, with females being more affected than males. Combined use of alcohol and tobacco increased the risk of developing all, colon, and prostate cancers. A “U-shaped” multiplicative interaction was observed for breast cancer when alcohol and tobacco were used in combination.
Source: The individual and combined effects of alcohol consumption and cigarette smoking on site-specific cancer risk in a prospective cohort of 26,607 adults: results from Alberta’s Tomorrow Project. Viner B, Barberio AM, Haig TR, Friedenreich M, Brenner DR. Cancer Causes Control. 2019 Sep 18.