Distant recurrence-free survival among postmenopausal women with oestrogen-receptor-positive breast cancers, in relation to the CYP2D6 genotype and adjuvant tamoxifen treatment. Solid line, patients receiving tamoxifen (Tam+); dashed line, patients who did not receive tamoxifen (Tam-). (a) Patients homozygous for the CYP2D6*1 allele. The number of events for Tam+ and Tam- were 25 and 27, respectively. (b). Patients homozygous or heterozygous for the CYP2D6*4 allele (null allele). The number of events for Tam+ and Tam- were 6 and 15, respectively.