New study suggests that Tamoxifen needs to be taken for 10 years for improved survival.

A recent study published in Lancet medical journal has shaken up the breast cancer field. Traditionally, in order to prevent recurrences and extend longevity, we have treated early breast cancer patients who have  hormone sensitive tumors with 5 years of the hormone blocker Tamoxifen. However, a recent study shows that 10 years of treatment results in improved rates of living longer without breast cancer.

The study involved 6,846 women with hormone sensitive breast cancer who had completed 5 years of Tamoxifen therapy. They were randomly chosen to either stop taking Tamoxifen or to continue with an additional 5 years, for a total of 10 years of Tamoxifen. The results showed that those women in the 10 year Tamoxifen group had less breast cancer recurrences and less breast cancer deaths. By year 15 breast cancer deaths had improved from 15% to 12.2% by the additional Tamoxifen treatment. The risks of taking more Tamoxifen included increased rates of uterine cancer (3.1% versus 1.6%) and pulmonary embolism [blood clot to the lung]. Overall though the amount of women dying from any causes were significantly smaller in the 10 year Tamoxifen group (639 versus 722).

Since this study has been presented, there has been much discussion about how to apply these results. Here are some thoughts:

Is the benefit of 3% (15% t0 12.2%) worth the additional 5 years of medicine. Our thoughts are that it depends upon how a woman tolerated Tamoxifen. If she barely noticed taking the medicine, then yes it makes sense. If she had side effects then 5 years would be fine.

What do we do with women who have DCIS or those who are taking an aromatase inhibitor? The real answer is that we don’t know.

Most people are leaning towards increasing the length of time for all hormonal medication because we know that hormone sensitive cancers can recur years after a diagnosis. In fact, half of all recurrences occur 8 years from initial treatment. We are also giving Tamoxifen for a few years followed by an aromatase inhibitor for a total of 5-8 years of treatment. This allows women to be exposed to less of the side effects of both drugs.

Should we extend it to 10 years, 15 years, forever…?

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