In an analysis of the SOLE phase 3 trial which evaluated the effect of extended intermittent or continuous letrozole on late relapse in postmenopausal women with hormone receptor-positive early breast cancer, FGFR1 copy number gain was significantly associated with an increased risk of late breast cancer events in univariate and multivariable models adjusted for clinicopathologic factors [40]. This evidence concerns the gene FGFR1 and breast cancer.