MTHFR and breast cancer: The present study aimed at investigating the association between TS 2R/3R, MTHFR C677T, RFC1 G80A and GSTT1 null, GSTM1 null or GSTP1 A313G polymorphisms with toxicity, disease free survival (DFS) and overall survival (OS) in Caucasian patients with early BC treated with CMF or FEC regimens.