New Findings on Breast Cancer Drug Tamoxifen

And now, we move onto the other big headline. The millimeters of americans battling breast cancer, getting this news. A new study saying a popular drug used to keep the disease from coming back should... See More

And now, we move onto the other big headline. The millimeters of americans battling breast cancer, getting this news. A new study saying a popular drug used to keep the disease from coming back should be taken twice as long for even better results. And the news has a lot of doctors saying they're going to change how they treat some of their patients. And abc's chief medical editor dr. Richard besser here to tell us about it. We know about this drug, but a chase change in the way you use it. Reporter: That's right. This is really big news for hundreds of thousands of women who have breast cancer that is hormone receptor positive. The study looked at the drug, which is a hormone blocker. They gave some women this drug for five years and some women this drug for ten years and then followed them for a ten-year period. Women on the drug for five years, 25% of them had a recurrence. Ten years, it dropped down to 21%. Very similar numbers, reduction, if you look at breast cancer deaths. 15%, for those on for five years. Down to 12% for those who were on it for ten years. To the layperson, we say, oh, we want better numbers, that doesn't seem like a huge change. Reporter: The numbers don't look big, but across the population, that's thousands of lives. What it sails to cancer researchers is, we might be onto something. This might be what we're looking for. Side effects from the drug? Reporter: You have to look at that. The serious side effects are rare. Blood clots and uterine cancer. The common side effects, this drug can bring on symptoms that are very much line men know pause. It can cause hot flashes, fatigue. I think today's study may get women to reconsider this drug. And what it says, is hormone therapy may work if you give it longer. Give it longer time. And as you said, clinging to anything that says we're onto something. Reporter: That's right. Thank you so much, rich.