Who has a doctor that believes in CYP2DX testing for Tamoxifen?

9lives70 · July 2017

I took this test and was determined to be an "intermediate' metabolizer of Tamoxifen which means it would likely have a reduced effectiveness for me. I realize this is controversial and there aren't enough definitive studies yet to fully support it ( I have read all of barred owl's great posts on it) however, it seems a very relevant piece of the puzzle to me. I know it's not standard of care but why would you recommend a drug that comes with so many side effects to a patient without knowing how well or if they can metabolize the drug and turn it into it's active form, endoxifen. I was told by the oncology pharmacist that I spoke to that I'd need more than twice the normal recommended dose to get the same effect as a normal metabolizer of the drug. I have a feeling insurance would not pay for that either.

I am 48 and pre menopausal trying to decide between Tamoxifen at twice the dose ( if the MO's recommend that when I meet later this month) or OS with AI. Not sure what to do.

Any thoughts would be appreciated.

wallycat · July 2017

10+ years ago when I started this ugly journey, little was mentioned about cyp2D6. I pulled the early research and presented it to my oncologist (then in WI). He was grateful and thanked me and ran the test (insurance covered it). When he got back from the breast cancer symposium, he profusely and unabashedly told me that I made him look smart (exact words from him!). That was a great deal of the talk back then in San Antonio and he felt empowered by the stuff I printed for him.

Yes, it is controversial, but you are allowed to make decisions about your health and body on your terms. Call your insurance and see if they cover it. If your onco won't order it maybe your breast surgeon or gyn will.

I don't think you need to take a double dose. Some tamoxifen studies show that 5mg. works well too. I see your dx is both ILC and IDC. Some posts here indicate tamoxifen isn't that great for ILC.

If the whole thing is confusing, you may want to discuss lupron shots to suppress your ovaries and go on an aromatase inhibitor.

Good luck with your journey.

snorkeler · July 2017

My MO said she orders the test if a patient shows absolutely no side effects from tamoxifen, but I always had the option of ordering it for myself if I wanted. She also mentioned that there is an alternative to tamoxifen which is metabolized differently. I can't remember the name, but I'm sure there are threads on this topic.

Who has a doctor that believes in CYP2DX testing for Tamoxifen?

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