Many women who were on Tamoxifen were only on it for the suggested 5 years and then it was time to celebrate the 5 tear survival marker. But the truth is that women are living longer after diagnosis but that there are higher risks for relapse. A study released in June 2013 looks at women staying on Tamoxifen for 10 years rather than the 5 years, as there is better protection for recurrence and dying from the disease.
The study looked at 7000 women and it showed that those who took the Tamoxifen for 10 years had 25 % less recurrences and 23% fewer died. Not numbers to to be ignored.
The concern is that Tamoxifen is not metabolized by everyone is still a concern and is a $60 blood test to see what type of metabolizer you are, but is not offered in Canada. This is where Canadian women need to be vocal as the recommended time to take Tamoxifen increases as consumers we need to be armed with knowledge to make better decisions.
Tamoxifen needs to be metabolized before it can be fully effective to treat breast cancer. An enzyme in your body called CYP2D6 is important to convert the Tamoxifen to Endoxifen, which then can block estrogen. There are four levels of metabolizers: ultra rapid metabolizer, normal metabolizer, intermediate metabolizer and poor metabolizer. The poor metabolizer notes that your body is unlikely to convert Tamoxifen to the useable form and that a different cancer treatment should be reviewed with your physician.
The CYP2D6 blood test is one factor in determining treatment.
Obtaining the CYP2D6 blood test is not available in Canada despite the fact that Tamoxifen is the most prescribed form of treatment for pre-menopausal breast cancer. At the Mayo Clinic Clinic, USA this blood test costs approximately $60. In certain circumstances patients in Canada maybe able to be tested, but at a cost of approximately $500 with blood work sent over the border. This would have to be arranged by your oncologist. While Tamoxifen is the most widely prescribed cancer medication in the world generating revenues of US $265 million in 1992 and in 1995, worldwide sales reached $400 million there is no information or access to a blood test that is essential for its effectiveness. It is unclear why this blood test is not standard procedure for women prescribed Tamoxifen or even mentioned on their literature.