As the majority of experimental studies suggest cadmium being metalloestrogen, we examined cadmium/breast cancer (BC) association by histological and tumor receptor subtype in 509 invasive BC patients and 1170 controls. Urinary cadmium was determined by atomic absorption spectrometry, and categorized using tertiles of its distribution in the controls: <0.18, 0.18-0.33, >0.33 kg × 10-9/kg × 10-3 creatinine. Relative to the lowest category of urinary cadmium adjusted odds ratio (OR) of ductal BC was 1.18 (95% confidence interval (CI): 0.89-1.58) in the intermediate and 1.53 (95% CI: 1.15-2.04) in the highest category. There was a significant association for hormone receptor-positive ductal BC: ORs per category increase were 1.34 (95% CI: 1.14-1.59) for estrogen receptor-positive (ER+), 1.33 (95% CI: 1.09-1.61) for progesterone receptor-positive (PR+) and 1.35 (95% CI: 1.11-1.65) for ER+/PR+ BC. We found a significant association between cadmium and human epidermal growth factor receptor 2-negative (HER2-) ductal BC. The strongest association with cadmium was for ER+/PR+/HER2- ductal BC. The associations between cadmium and lobular BC with hormone receptor-positive and HER2- were positive but insignificant. There was no evidence that the associations with cadmium differed for cancers with different tumor histology (p-heterogeneity > 0.05). This study provides evidence that urinary cadmium is associated with the risk of hormone receptor-positive and HER2- breast cancer independent of tumor histology.
Keywords: breast cancer; case-control study; tumor receptors; urinary cadmium.