Tamoxifen Sensitivity Assay/ Pharmacogenetics


I’ve discovered that you can have a tamoxifen sensitivity test / assay, that looks at your genetics and whether certain drugs could benefit you, in this case tamoxifen. 

The Pink ribbon foundation partnered with Myogenes on the hereditary cancer test, so I also found they had a pharmacogenetic test which lists tamoxifen. Cost for this test is £450 plus vat & covers nearly 300 drugs. myogenes.com/our-tests/the-pharmacogenetics-test/

The BCN helpline gave me the contacts for paternity for life, who offer a test from genomics (Australia) in the U.K. You can request the test on line via the pharmacogenetics test but you pay one fee for tamoxifen specifically. paternityforlife.co.uk/services/clinical-tests/pharmacogenomics-drug-response/ So £249 for the 1 test, the test that is generic covers 40 drugs but tamoxifen isn’t included in their 40.

I have been putting off taking tamoxifen for a few months & have now ordered the test. Myogenes said it’s rarely ordered on NHS but some private insurers will pay apparently.

Hope it’s of interest to the wider community.

That’s very interesting thank you for sharing .

Hi greenfairy

I will be intrigued to know your outcome. 

I could well be following you down this path. 

Keep us posted

Hi, so I finally got my results back. After I’d ordered the test I found 70-80% people are expected to metabolise tamoxifen normally, (ncbi.nlm.nih.gov/books/NBK247013/) so if I’d found this before I likely wouldn’t have ordered the test but my sample had gone off anyway.  As it turned out I am in 6-10% that are poor metabolisers. Based upon that and co-incidentally lining up with a visit to a breast surgeon at the Royal Marsden, they stated for me, it was tamoxifen or nothing based on my results, (although I can check this with oncology). For DCIS, tamoxifen is not routinely given, but due to the small invasive element they’d found, they’d recommended it for that. At my age, early forties, the surgeon said the alternative of an AI and ovarian suppression would impact my life. So that’s decided it for me, the result tells you how poorly you’d metabolise and mine was the poorest. For me, I am glad I checked prior to starting adjuvant therapy.

This is in relation to my results - info via above link does also state that for poor metabolisers the dose can be doubled or more, with endoxifen measured. Or an AI used with ovarian suppression. The above link equally states that some studies do not think there is a genetic implication on metabolism of tamoxifen or look at other genes. So different opinions but it is something I found, followed up and these were my results.
We are all different, hope sharing this is useful.

Hi, join the club. I’m a (very) poor Tamoxifen metabolizer, so I get all of the side-effects (some dangerous) and no benefits! I live in Panama now, so I’m able to get alternatives that are not yet (soon though) FDA approved, though really, they should be. If our bodies cannot make Endoxifen (the active metabolite) from Tamoxifen, why not just take Endoxifen? It does not have the serious side effects (like uterine overgrowth etc) and is way more effective than Tamoxifen! I take 8mg every 3rd day and had a second test done for Endoxifen levels (which need to be a minimum of 15nMol, mine were around 1 on Tamoxifen) and mine is now 50-70nMol, which, if I were an excellent metabolizer of Tamoxifen, would only be possible with more than 40mg a day, and that would cause a LOT of side effects anyway. The MAYO clinic is blazing a trail for this approach, Watch: https://www.youtube.com/watch?v=feya6q-BfpI

Please research Endoxifen and try to join the trials by Mayo Clinic and others, it will save your life! I’ve had 2 Er+ tumors, in 2 breasts, 5 years apart, 1 the rarest kind, the second the most common kind (same as yours) and Endoxifen has stopped both from returning or spreading! It’s nothing short of a Miracle! My sister died in August at age 63, 4 years younger than me, in Canada, supposedly with their “Superior Medical care”, which is so hopelessly outdated that she stood no chance. SEE: Breast Cancer Breakthroughs: Endoxifen: An Effective, Affordable, Safer drug for All stages of HR+ Breast cancers! God Bless!