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Tamoxifen (Nolvadex) response- Medical Indications

 Tamoxifen (Nolvadex®) response              

(not available at this time)
  • Medical Indications:  The primary use of tamoxifen is as an adjuvant treatment for ER positive breast cancers.  It is also prescribed to some woment to reduce the chance of developing breast cancer.   
  • Mechanism of action:   Testing breast tumor biopsies can classify certain breast cancers as estrogen receptor (ER) positive.  These cancers produce the ER protein, and require estrogen to grow.  Tamoxifen competes with estrogen for binding to the ER in breast tissue.  It is an antiestrogen or SERM (Selective Estrogen Receptor Modulator) and is used to prevent the growth of ER positive breast cancers. 
  • Adverse reactions:  The most common side effects of tamoxifen are blood clots, strokes and cataracts.   Use of tamoxifen increases the risk of developing endometrial cancer and uterine sarcoma. 
  • Pharmacogenetics:  Tamoxifen is a "pro-drug" that is not clinically effective until converted to the active drug metabolite in the liver.  The CYP2D6 gene encodes the principal cytochrome P-450 enzyme that metabolizes tamoxifen.  It is estimated that up to 30% of the population have at least one genetic variant of CYP2D6 with reduced or no activity in converting tamoxifen to the active drug.  These individuals may derive little or no clinical benefit from tamoxifen, and are unnecessarily exposed to the adverse effects. 
    • Information this test provides
    • Considerations based on your test result
(not available at this time)

Additional pharmacogenetic information:

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