Modifiable factors appear to be associated with a reduced risk of breast cancer (BC), even in women at higher genetic risk. That is the finding of a new cohort study of data in the UK Biobank.
The study included data for 2728 women with BC and 88,489 women serving as controls. Median follow-up time was 10 years (maximum 13 years).
Women with BC were found to have higher body mass index (relative risk [RR] 1.14; 95% CI 1.05-1.23), performed less exercise (RR 1.12; 95% CI 1.01-1.25), used hormonal replacement therapy for >5 years (RR 1.23; 95% CI 1.13-1.34), used more oral contraceptives (RR 1.02; 95% CI 0.93-1.12), and had greater alcohol intake (RR 1.11; 95% CI 1.03-1.19) compared with the controls.
The RR of the highest genetic risk group was 2.55 (95% CI 2.28-2.84), and the RR of the healthiest lifestyle category was 1.44 (95% CI 1.25-1.65). The association of lifestyle and BC within genetic subgroups showed lower HRs among women following a healthy lifestyle. Women with the most unfavourable lifestyle had a higher risk of BC in the low genetic (HR 1.63; 95% CI, 1.13-2.34) and high genetic risk (HR 1.39; 95% CI 1.11-1.74) groups.
The authors said the results suggest that promotion of healthy lifestyles through adequate levels of exercise, healthy weight, lower alcohol intake, and avoidance of hormonal replacement therapy should be encouraged to reduce the risk of BC.
