Cigarette smoking, physical activity, and alcohol consumption as predictors of cancer incidence among women at high risk of breast cancer in the NSABP P-1 Trial
A partir des données de l'essai "NSABP P-1" incluant 13 388 femmes à haut risque de cancer du sein (durée médiane de suivi : 7 ans), cet essai évalue l'association entre le tabagisme, une activité physique, une consommation d'alcool, et le risque de cancer
Background: NSABP P-1 provides an opportunity to examine the association of behavioral factors with prospectively monitored cancer incidence and interactions with tamoxifen. Methods: From 1992-1997, 13,388 women with estimated 5-year breast cancer (BC) risk greater than 1.66% or a history of lobular carcinoma in situ (87% under age 65; 67% post-menopausal) were randomly assigned to tamoxifen versus placebo. Invasive BC, lung (LC), colon (CC), and endometrial cancers (EC) were analyzed with Cox regression. Predictors were baseline cigarette smoking, leisure-time physical activity, alcohol consumption, and established risk factors. Results: At median 7 years follow-up, we observed 395, 66, 35, and 74 BC, LC, CC, and EC, respectively. Women who had smoked were at increased risk of BC (P=.007; hazard ratio (HR)=1.3 for 15-35 years smoking, HR=1.6 for ≥35 years), LC (P<.001; HR=3.9 for 15-35 years; HR=18.4 for ≥35 years), and CC (P<.001; HR=5.1 for ≥35 years) versus never-smokers. Low activity predicted increased BC risk only among women assigned to placebo (P=.021 activity main effect, P=.013 activity-treatment interaction; HR=1.4 for placebo group) and EC among all women (P=.026, HR=1.7). Moderate alcohol (>0-1 drink/day) was associated with decreased risk of CC (P=.019; HR=.35) versus no alcohol. There were no other significant associations between these behaviors and cancer risk. Conclusion: Among women with elevated risk of BC, smoking has an even greater impact on BC risk than observed in past studies in the general population. Impact: Women who smoke or are inactive should be informed of the increased risk of multiple types of cancer.