INS and breast carcinoma: Of the total 12 studies, Currie et al.,61 Ruiter et al.,85 Hsieh et al.,60 Tsilidis et al.,86 and Kowall et al.87were not included in the present study because their reference groups were sulfonylurea or insulin‐based treatment users, while we only considered nonmetformin users as comparators as we suspect other glucose‐lowering medicines may increase or decrease the risk of breast cancer.88