Background: The incidence of CYP2D6*4 among Caucasians is estimated up
to 27%, while it is present in up to 90% of all poor metabolizers
within the Caucasian population. The hypothesis under question is
whether the presence of one or two non-functioning (null) alleles
predicts an inferior outcome in postmenopausal women with breast cancer
receiving adjuvant treatment with tamoxifen. The aim of the present
study is to estimate the incidence of CYP2D6*4, in the Greek
population and more precisely among females suffering from breast
cancer. Materials and Methods: Eighty unrelated mainland Greek female
volunteers suffering from hormone-sensitive breast cancer were recruited
during their primary handling or follow-up examination in order to
provide samples for purification and polymerase chain
reaction/restriction fragment length polymorphism (PCR-RFLP) of genomic
DNA derived from buccal swabs. Results: The incidence of individuals
with at least one present allele*4 within the Hellenic population was
estimated to be as high as 30% (n = 24/80), with a 95% confidence
interval of 20% to 40%. From the statistical point of view, it can be
securely stated that incidence of *4 among Greek women is over 20%.
The incidence of homozygous carriers of *4 in the present sample
occurred in 8.75%, while the incidence of allele*4 haplotype occurred
in 19.4% (n=160). Conclusion: Although the outcoming results for Greek
women are actually in line with existing data for other European
nations, it should be noted, that a routine CYP2D6 testing of women
suffering from breast cancer is formally not recommended, as the
clinical significance of CYP2D6 phenotype in treatment and outcome of
breast cancer remains unclear
