Genetic differences in enzyme CYP2D6 play a key role in effectiveness of tamoxifen fo
 

For nearly a decade, breast cancer researchers studying the hormone therapy tamoxifen have been divided as to whether genetic differences in a liver enzyme affect the drug's effectiveness and the likelihood breast cancer will recur.

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Personalized Cancer Care Questions Tamoxifen CYP2D6 testing
 

It was hoped some day that Genomic Analyses of cancer tumors would be able to identify in advance which patients will benefit from use of cancer drugs (clinical responders). The Agency for Healthcare Research and Quality (AHRQ) suggests that day is still a ways off.

A study looked at whether the presence of specific mutations in people who had breast and colon cancer and chronic myeloid leukemia determined if patients would respond to expensive new drugs commonly used to fight the diseases. Only in colon cancer did the mutation matter and in that case, while it ruled out the effectiveness of drug therapy, the relevant mutation only appears in a small percentage of cases.

In the finding, the AHRQ report found there was "no consistent associations" between breast cancer patients with the relevant CYP2D6 polymorphism and the outcome of tamoxifen therapy, whether as primary treatment or in as post-operative adjuvant therapy.

Estimates vary, but anywhere from 10 to 40 percent of women have the gene variant of CYP2D6 that is believed to slow the metabolism of tamoxifen and make it less effective.

http://cancerfocus.org/forum/showthread.php?t=3061

Re: Genetic differences in enzyme CYP2D6 play a key role in effectiveness of tamoxife
 

So.. this most recent study is finding a significant correlation between the gene variant and tamoxifen metabolism? Looking back at the past threads I had interpreted previous studies as not finding a significant correlation? Does this open the door again on CYP2D6 testing, especially for Her2+ populations? My oncologist never mentioned this issue at all, I only learned of the gene alteration from this and other discussion boards. I'm torn on how hard to push for this test as I'm premenopausal and it would open up a Pandora's box of issues if tamoxifen is not an option.

Re: Genetic differences in enzyme CYP2D6 play a key role in effectiveness of tamoxife
 

My insurance company asked me to undergo the CYP2D6 test after it had been prescribed for me again following my recurrence in 2007.

My doctor put me right back on it until his replacement (after his semi-retirement moving back to his hometown) told me to switch to Exemestane.