IGF1 and breast carcinoma: In summary, the main findings of our study were thus a weak but nominally significant association of a block of polymorphisms located at the 5′ end of the IGF1 gene with breast cancer risk, particularly among women younger than 55 years, and an association of polymorphisms located in the 5′ region of IGFBP3 with circulating levels of IGFBP-3.