Letrozole efficacy is related to human aromatase CYP19 single nucleotide polymorphisms (SNPs) in metastatic breast cancer - R Colomer; M Monzo; I Tusquets; J Rifa; JM Baena; A Barnadas; L Calvo; F Carabantes; C Crespo; M Muñoz; A Llombart; A Plazaola; et al. (Breast Cancer Research, 2005)