CYP2D6 and neoplasm: A comparison of the RRs of distant recurrence, calculated for each combined genotype and adjusted for age, tumour size and lymph node status, demonstrated that the risk reduction with tamoxifen was significantly higher in patients harbouring the combination of CYP2D6*4 and/or SULT1A1*1/*1 (P = 0.018) (Fig. 3a,b and Table 2).