Lifestyle factors and the risk of a second breast cancer after ductal carcinoma in situ.

Background: Little information exists on lifestyle factors that affect prognosis after treatment for ductal carcinoma in situ (DCIS) breast cancer. Improved understanding of the role of lifestyle factors is important to survivors wishing to reduce their risk of a second breast cancer diagnosis.

Methods: We examined the association between body mass index (BMI), physical activity, and alcohol intake, and risk of a second breast cancer diagnosis among 1,925 DCIS survivors in the Wisconsin In Situ Cohort. Exposures were self-reported during biennial patient interviews. Second breast cancer diagnoses were validated via pathology report. Cox proportional hazards regression was used to estimate the association between prediagnosis, postdiagnosis, and change in exposure levels and the risk of a second diagnosis, with adjustment for patient, tumor, and treatment factors.

Results: Over a mean of 6.7 years of follow-up, 162 second breast cancer diagnoses were reported, including 57 invasive events, 60 in situ events, and 45 diagnoses of unknown stage. A significant trend of increasing risk of a second diagnosis was found over increasing categories of postdiagnosis alcohol intake (Ptrend = 0.02). Among premenopausal women, increased prediagnosis BMI was associated with a reduced risk of a second diagnosis (HR = 0.93; 95% confidence interval, 0.88-0.99).

Conclusion: DCIS survivors may reduce their risk of a second diagnosis by reducing postdiagnosis alcohol consumption.

Impact: The population of DCIS survivors is projected to surpass one million by the year 2016. Our results suggest that these women may be able to reduce their risk of a second diagnosis through moderation of alcohol consumption.