Certain tumor factors have been associated with increased likelihood of a second breast diagnosis after treatment for ductal carcinoma in situ (DCIS) breast cancer. However, little information exists on modifiable lifestyle factors that affect prognosis after DCIS and may be useful for survivors in reducing their risk of a second breast cancer event.
We examined the longitudinal association between body mass index (BMI), physical activity, and alcohol intake and risk of a second breast diagnosis among 1,925 DCIS survivors first diagnosed in 1997–2006 and enrolled in the Wisconsin In Situ Cohort. Data were collected during biennial patient interviews and diagnosis information was validated via pathology report. BMI, physical activity, and alcohol intake were examined over time using Chi-square and ANOVA methods. Cox proportional hazards regression was used to estimate the risk of a second diagnosis after adjustment for patient, tumor, and treatment factors. Repeated measures were incorporated to make use of exposure measurements taken at each post-diagnosis interview.
Over an average of 6.6 years of follow-up, 162 second breast cancer diagnoses were reported. Significant trends of increasing BMI and decreasing physical activity were observed over time since diagnosis (p < 0.001). For all women, a significant linear trend of increasing risk of a second diagnosis was found over increasing categories of post-diagnosis alcohol intake (p-trend 0.02). Among women treated with ipsilateral mastectomy, a reduction in risk was suggested with increasing post-diagnosis physical activity (HR 0.67, 95% CI 0.45, 1.02 for each additional hour/week). Among postmenopausal women, higher categories of post-diagnosis BMI were associated with increasing risk, although these results were of borderline significance (p-trend 0.09).
This study is the first to examine the association of physical activity and alcohol intake with second breast diagnoses in an exclusively DCIS population. Our results suggest that DCIS survivors may reduce their risk of a second diagnosis by engaging in physical activity and reducing their alcohol consumption.
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