Survival of women with breast cancer in relation to smoking

Objective: To compare survival of patients with breast cancer who had never smoked, were smokers, and who were ex-smokers. Design: Observational study. Setting: City of Malmo, Sweden. Patients: 792 patients with breast cancer diagnosed between 1977-1986 in th e Malmo mammographic screening trial. Interventions: Follow-up of breast cancer cases through record-linkage with the Swedish Cause of Death Registry. Main outcome measures: Death from breast cancer. Relative risk (RR) with 95 % confidence interval (CI) of death from breast cancer was calculated for d ifferent smoking groups using Cox's proportional hazards analysis. Results: During a mean follow-up of 12.1 years, 145 patients died of breast cancer. Breast cancer mortality was 1347/10(5) person-years in those who h ad never smoked, 1941/10(5) in smokers, and 1493/10(5) in ex-smokers. The c rude RR for smokers and ex-smokers, compared with those who had never smoke d were 1.44 (1.01 to 2.06) and 1.13 (0.66 to 1.94), respectively. The RR as sociated with smoking remained significant after adjustment for age and sta ge at diagnosis, 2.14 (1.47 to 3.10), and other potential confounders. Conclusions: Survival after breast cancer was, as expected, strongly relate d to stage at diagnosis. However, stage by stage there was considerable var iation between individual patients. We conclude that differences with regar d to exposure to smoking contribute to this heterogeneity.