Gene variant means tamoxifen less likely to work

Reported by Susan Aldridge, PhD, medical journalist

A study of women with breast cancer shows that a response to tamoxifen is less likely among those carrying a specific gene variant.
Tamoxifen is a drug which can help women fight a recurrence of breast cancer. Researchers at the University of Michigan Comprehensive Cancer Center and the Mayo Clinic now discuss how a gene variant influences responses to the drug.

The gene controls production of an enzyme called CYP2D6, which is responsible for activating tamoxifen into a much more potent anti-estrogen. Tamoxifen itself works by blocking estrogen, which otherwise can stimulate the growth of breast cancer cells. Up to ten per cent of women inherit a variant of the CYP2D6 gene which this current study finds linked to a higher likelihood of recurrence of breast cancer. Those carrying the variant are twice as likely to suffer a recurrence.

This study also found that women with this CYP2D6 variant are twice as likely to see their breast cancer come back. They are also less likely to have hot flashes as a side effect of tamoxifen, something that could be diagnostic of having this gene variant. It's hoped that this research might lead to a genetic test that could be carried out to discover which women are most likely to benefit from tamoxifen treatment.

Source
Journal of Clinical Oncology 20th December 2005