I appreciate the review on the ongoing controversial subject of tamoxifen treatment of post-menopausal breast cancer and CYP2D6 genotyping by Brauch & Schwab [1]. However, I am somewhat surprised that on at least two central issues the authors do not discuss original findings that fail to support their position.
While I do not claim that there is no issue with tumour-line derived genotyping as opposed to germ-line genotyping, at least two different studies have been published that suggest a high degree of concordance [2,3]. I believe such data and positions warrant discussion in the context of the present review.
On the issue of concomitant treatment with tamoxifen and CYP2D6 inhibitors for support of the biological rationale as suggested by the authors, one study demonstrated an effect of paroxetine, but an interaction effect could not be demonstrated for fluoxetine, a very potent and effective inhibitor of CYP2D6 [4]. Another study did not confirm an interaction between CYP2D6 inhibitors and breast cancer recurrence in tamoxifen treated patients [5].
Additionally, despite the determined opinion of the authors on the Hardy–Weinberg equilibrium (HWE) issue as related to various clinical sets of data, this may not be as clear as they would like it to be [6,7]. In fact, the publication highlighted by the authors for credibility on this matter [8], itself contains a sample violating the HWE [9].
Despite the authors' introductory acknowledgement of an ongoing controversy, the uninitiated reader is left with the impression that the pro et contra of CYP2D6 genotyping prior to tamoxifen treatment in postmenopausal breast cancer, is now settled once and for all in favour of the pro. The conclusion of the meta-analysis recently published by the International Tamoxifen Pharmacogenomics Consortium [10], to which the two authors themselves belong, appears more balanced.
Competing Interests
The author has completed the Unified Competing Interest form at http://www.icmje.org/coi_disclosure.pdf (available on request) and declares no support from any organization for the submitted work.
References
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