Obesity as a risk factor for triple-negative breast cancers: a systematic review and meta-analysis.

Triple-negative breast cancer (TNBC) is a subtype of breast tumor with unique characteristics in terms of clinical-pathological presentation, prognosis, and response to therapy. Epidemiological investigations focusing on the identification of risk factors involved in the onset and progression of TNBCs have identified unique demographic, anthropometric, and reproductive characteristics involved in the etiopathogenesis of this subtype of breast tumors. This systematic review and meta-analysis evaluates the association between TNBCs and obesity and menopause status. Eligible articles were identified through three databases and secondary reference analysis. The search was conducted from the first record to February 2012. Eleven original articles meeting a priori established inclusion criteria were incorporated in the quantitative analysis. Case-case and case-control comparisons were performed. In addition, a case-case comparison was conducted before and after stratification according to menopausal status. Based on the level of between-study heterogeneity, pooled odds ratio (OR) and 95 % confidence interval were calculated using fixed or random models. The case-case comparison showed a significant association between TNBC and obesity (OR: 1.20; 95 % CI: 1.03-1.40). These results were confirmed by the case-control comparison (OR: 1.24; 95 % CI: 1.06-1.46). Once stratification based on menopausal status was applied to the case-case analysis, significant results were observed only in the pre-menopausal group (OR: 1.43; 95 % CI: 1.23-1.65). According to this analysis, obese women are at a greater risk of presenting with a TNBC than non-obese women, and menopause status may be a mitigating factor. If validated, these findings should be taken into consideration for the development of targeted preventive programs.