Once treatments are over, many breast cancer patients with hormone-receptor positive cancers are recommended to take a drug called Tamoxifen for about 5 years. Our oncologist very wisely informed me that the Cytochrome P450 2D6 (CYP2D6) is an enzyme that is involved in the metabolism of numerous drugs, of which Tamoxifen is one. Here is some clinical information which may sound like blither blather to most, but could be helpful to people on Tamoxifen or for whom Tamoxifen is in the plan.  Please understand that this is MY understanding and the purpose for putting it in here is to raise awareness.

Some people have inadequate CYP2D6 activity so these drugs may have reduced efficacy when these patients take them. Sometimes patients are not tested for this, and so it goes undetected. My oncologist asked for an extra vial of blood at my last infusion in order to identify whether or not I had adequate CYP2D6 activity. She told me that if I did not have adequate activity, she would recommend a different medication and one to essentially “shut off” my ovaries. (The idea of shutting off my ovaries struck me as something to avoid if at all possible.)

I think it’s also important to mention that many drugs can interfere with the CYP2D6 activity like some antidepressants and some heart medication, so that may be something to check out as well.

It amazes me that science can see this information in my blood.  Although I’m really tempted to copy some of the lab report here just to impress readers, I’m going to spare you.  It’s quite a remarkable report albeit full of words I cannot pronounce.  The GOOD news is that my CYP2D6 is doing just fine and is considered in the report to be a normal metabolizer with extensive enzymatic activity.

I hope this helps someone somewhere.

Next up:  the Verification appointment on Tuesday where we learn whether the sights and beams are set correctly to hit the targets and miss the rest of me.