Breast cancer a smoking-related disease
The increased risk of breast cancer associated with smoking is similar across racial/ethnic groups and by oestrogen (ER) and progesterone (PR) receptor status, a study has found. This suggests that breast cancer should be considered as a smoking-related disease.
Researchers looked at 67,313 women aged 45–75 years who were enrolled in the Multiethnic Cohort (MEC) study, identifying breast cancer cases and tumour receptor status via linkage to the Hawaii and California Surveillance, Epidemiology and End Results Program cancer registries.
During a mean follow-up of 16.7 years, 4,230 women developed invasive breast cancer. Cox regression analysis showed that the risk of breast cancer overall was higher in parous ever smokers who had smoked >5 years prior to their first live childbirth than in parous never smokers (hazard ratio [HR], 1.31; 95 percent CI, 1.14–1.51).
Moreover, the risk increase was pronounced for African Americans (HR, 1.51; 1.05–2.16), for Native Hawaiians (HR, 1.66; 1.10–2.50), for whites (HR, 1.42; 1.13–1.78), for ER-positive tumours (HR, 1.37; 1.17–1.61) and PR-positive tumours (HR, 1.33; 1.11–1.59).
The estimates showed that the risk of incident breast cancer did not differ by racial/ethnic groups (p=0.15) or tumour receptor status (p=0.60 by ER status; p=0.95 by PR status).
The MEC data indicate that breast cancer should be considered as a smoking-related cancer, researchers said.