Alcohol consumption, body mass index and breast cancer prognosis: results from the SEARCH study


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Alaa Ali1,2, Mitul Shah3, Douglas Easton3, Paul Pharoah1,3
1Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK, 2South Egypt Cancer Institute, Assiut, Egypt, 3Department of Oncology, Cambridge, UK

Background

Risk factors for breast cancer include alcohol consumption and body mass index (BMI). Some evidence suggests that they also affect prognosis. The purpose of this study was to investigate the effect of alcohol consumption and BMI on survival after breast cancer diagnosis.

Method

We used data from women with invasive breast cancer who had taken part in SEARCH (1). The association between both alcohol intake and BMI, and overall and breast cancer specific was investigated using Cox regression. We modelled each as a continuous variable and as an ordinal variable (alcohol consumption - <7, 7-13 and 14+ units per week; BMI - quartiles). We also stratified the analyses by estrogen receptor (ER) status. Analyses were censored at 15 years.

Results

Data on 13,525 cases were available for analysis with 6.7 years median follow-up. In univariate analyses, improved prognosis was seen with increasing current alcohol consumption, with a 2% (95% CI, 1-3%) reduction in the risk of death per unit of alcohol consumed per week. The HR unit increase in ordinal category was 0.87 (95% CI: 0.81-0.96). The association with better prognosis was slightly stronger in patients with ER negative tumours (HR: 0.74; 95% CI: 0.60-0.90) compared with patients with ER positive tumour (HR 0.91; 95% CI 0.82-1.01) (P=0.067). Adjusting for tumour stage and histopathological grade gave similar estimates. BMI was associated with a 1.9% (95% CI, .9% to 2.9%) increase in mortality per unit increase. This effect was attenuated and not statistically significant when adjusted for stage and grade. The results were similar for breast cancer specific survival.

Conclusion

The prognosis of breast cancer is poorer in women who are overweight, but better in women with moderate alcohol consumption. These findings are consistent with previously published data. If confirmed, these findings may have implications for counselling women being treated for breast cancer.