We evaluated the association between dietary patterns and breast cancer (BC) subtypes among women from Northern Mexico. From a study of incident cases and population controls that was carried out from 2007 to 2011, a subsample of 509 cases matched 1:1 by age with 509 controls was selected. Information about expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor 2 (HER2) was available from medical records to classify BC on luminal (ER + and/or PR+/HER2–), HER2+ (ER+/– and/or PR+/–/HER2+), or triple negative (ER– and PR–/HER2–). Dietary information was gathered using a semiquantitative food frequency questionnaire and a factor analysis was used to obtain dietary patterns. The association between each dietary pattern and BC molecular subtypes was assessed through conditional logistic regression models. Two dietary patterns were identified. The first (mainly characterized by meat, high fat, and sugary cereals) was positively associated with BC (odds ratio, OR = 12.62; 95% CI: 7.42, 21.45); the second (consisting of corn, legumes, and other vegetables) was inversely associated with BC (OR = 0.50; 95% CI: 0.40, 0.62). Both associations remained significant by BC molecular subtypes. These findings could contribute to the development of public health strategies for BC prevention.

Cadmium (Cd), a carcinogenic metal also related to reproductive and cardiovascular diseases, is contained in tobacco and elevated concentrations of it in humans have been consistently associated with first-hand tobacco smoke; however, there is scarce and inconclusive evidence of the relationship between Cd and secondhand smoke (SHS) exposure. Our aim was to evaluate the association between exposure to tobacco, both active and SHS, with urinary Cd concentrations in Mexican women. In a cross-sectional analysis that included 998 women living in northern Mexico, we measured the concentration of creatinine-adjusted urinary Cd (µg-cadmium/g-creatinine) using inductively coupled plasma triple quadrupole (ICP-QQQ) in tandem mass spectrometry mode (MS/MS). We gathered tobacco smoking information through an in-person interview and formed seven groups: non-smokers without SHS exposure; non-smokers with SHS exposure; ex-smokers without SHS exposure <1 year of quitting; ex-smokers without SHS exposure ≥1 year of quitting, ex-smokers with SHS exposure <1 year of quitting; ex-smokers with SHS exposure ≥1 year of quitting and current smokers. The interview also yielded sociodemographic characteristics. We used linear multivariable regression models to estimate the association between Cd concentrations and tobacco smoke exposure. Compared to non-smokers without SHS exposure, we found higher Cd concentrations in ex-smokers with SHS exposure <1 year of quitting and current smokers (adjusted geometric means 0.51 vs. 1.01 and 0.69 µg-cadmium/g-creatinine, respectively). Our results do not support a conclusion that SHS exposure is a source of Cd body burden.

The question of whether dichlorodiphenyltrichloroethane (DDT) exposure is related to breast cancer (BC) remains unanswered, possibly due to methodological constraints in the studies that have been performed. We aimed to update and synthesize the available epidemiological evidence on the relationship of p,p′-DDT, o,p′-DDT and p,p′-dichlorodiphenyldichloroethylene (p,p′- DDE) biological concentrations with female BC, focusing in methodological characteristics not addressed in previous reviews. We conducted an overview of reviews and a systematic review and meta-analysis. We used six databases and one search engine to identify meta-analyses based on systematic reviews, pooled analyses, and individual studies published from January 2000 to December 2021. For the overview of reviews, we assessed meta-analyses’ risk of bias and carried out a narrative synthesis. For the meta-analysis, we estimated summary association measures with fixed or random effects models for each compound stratifying for characteristics of interest. We estimated a positive summary association between p,p′- DDT biological concentrations and BC in prospective studies (nested case control) with >10 years of follow-up (sOR=1.41; 95 %CI: 1.06–1.88). Among retrospective studies (hospital or population-based case-control), BC was positively related with p,p’-DDE biological concentrations (sOR=1.15; 95 %CI: 1.02–1.30), and with p,p’-DDT in women with mean serum concentrations>100 ng/g (sOR=1.33; 95 %CI: 1.25–1.41). Moreover, we detected a positive association between o,p′-DDT and BC (sOR=2.24; 95 %CI: 2.15–2.34). Our results support a positive relationship between DDT exposure and BC, and are useful to reinforce its worldwide prohibition, since this pesticide is still used in some countries, has long persistence in the human body and disseminates to other geographic areas.