What are the guidelines for use of tamoxifen as a breast cancer risk reduction strategy?

Updated: Dec 07, 2018
  • Author: Maurie Markman, MD, MS; Chief Editor: Keith K Vaux, MD  more...
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Answer

Answer

Currently, the National Comprehensive Cancer Network (NCCN) does not recommend testing for CYP2D6 variants in patients considering tamoxifen in the adjuvant setting, which matches the recommendation from the American Society of Clinical Oncology (ASCO) about not testing for CYP2D6 variants in patients considering tamoxifen as a breast cancer risk reduction strategy. [2, 22]  

There is evidence that SSRIs paroxetine and fluoxetine interfere with the enzymatic conversion of tamoxifen to endoxifen by inhibiting a particular isoform of CYP2D6. The NCCN guidelines recommend that medications that have minimal or no impact on plasma levels of endoxifen should be substituted whenever possible. [2] These alternatives include ciitaloprom, venlafaxine and escitalopram. [23]


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