Letrozole: Vital Findings

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• RAY SUAREZ:

  Researchers announced today that a drug called Letrozole reduced the recurrence of tumors among survivors of early stage breast cancer by 43 percent. The drug was used after patients had five years of therapy with another drug, Tamoxifen. For more than half of breast cancer patients, the disease returns within five years after the initial diagnosis. But in today's study of more than 5,000 women, doctors found that only 75 taking Letrozole relapsed, compared to 132 in the placebo group.

  For more on these findings, I'm joined by Dr. Andrew von Eschenbach. He's the director of the National Cancer Institute, which led the study in the U.S. What was the original trial trying to determine?

• DR. ANDREW VON ESCHENBACH:

  Well, Ray, this is a very important trial for a subgroup of women with breast cancer who have had standard therapy, have been doing well on that therapy, but at the end of five years went Tamoxifen had to be stopped, there was no additional therapy available to those women and yet half of them would be at risk for a recurrence from the breast cancer. This study introduced a new way of being able to provide protection for that group of women.

• RAY SUAREZ:

  So how were the women chosen? What was their health status at the time they started the trial?

• DR. ANDREW VON ESCHENBACH:

  These were women who had developed their breast cancer after the menopause. Their breast cancers had still a receptivity to estrogen or hormone. They had been on Tamoxifen for five years as a way of blocking any recurrence and then at that point when they came off the Tamoxifen, they were then randomized. Half were given a placebo and the other half were placed on the drug Letrozole. And then they were followed carefully to determine the incidence of recurrence of disease.

• RAY SUAREZ:

  And the recurrence was?

• DR. ANDREW VON ESCHENBACH:

  Well, very fortunately in the study as the two groups were monitored very carefully and overseen by an independent monitoring board, it was noted that in the groups that were receiving Letrozole the incidence of recurrence was half that was occurring in the women on the placebo. Because of that observation of the benefit that was occurring from the drug, the drug was stopped prematurely and the results were made available.

• RAY SUAREZ:

  So you stopped the trial before its planned course?

• DR. ANDREW VON ESCHENBACH:

  Correct. One of the opportunities here with this very carefully and well designed study within a very appropriate independent oversight monitoring and checking on the results. As soon as there was statistically significant evidence of a benefit, the study was stopped so that benefit could be made available to all the women on the study including the ones who up to that point in time were receiving the placebo.

• RAY SUAREZ:

  When you get good news in the clinical trial setting do you have to do another test just to reproduce the original set of findings, satisfy all interested parties that this is something that is really for real?

• DR. ANDREW VON ESCHENBACH:

  I think it's important to keep in mind the need for cautious optimism when we stop a study early. It stopped because of very sound evidence that there's a significant benefit with regard to being able to impact on the disease. But by stopping early we don't have the long-term follow up that we might normally have to watch for late-term side effects. There's a balance here between benefit and potential risks. One of the things that will be done with this particular study is that we'll continue to monitor women on the drug as they go on to look for any possibilities of late term side effects.

• RAY SUAREZ:

  Let's talk about the substance itself let Letrozole. What is it doing inside the body that researchers believe is stopping or lowering the rate of relapse among women who have already used Tamoxifen?

• DR. ANDREW VON ESCHENBACH:

  We know these cancer cells, these breast cancer cells can still be responsive to estrogen that acts almost like gasoline on a fire. Tamoxifen blocks the binding of the estrogen to the cancer cell at the receptor. But Letrozole works in a completely different way. It doesn't block at the receptor but it blocks the development of the estrogen. It has the same effect of depriving the cancer cell of the gasoline, the estrogen, but it does it in a completely different way than Tamoxifen.

• RAY SUAREZ:

  Are there side effects that are significant? You mentioned some. How do you balance them against the benefit?

• DR. ANDREW VON ESCHENBACH:

  Well, some of the risks that may occur with a drug that reduces the ability of estrogen to infect cells could result for example in osteoporosis and a change in blood lipid levels or cholesterol levels. So those are two effects of the drug that need careful observation and monitoring.

• RAY SUAREZ:

  So any woman who is on it would get those signs checked from time to time?

• DR. ANDREW VON ESCHENBACH:

  Exactly. A woman on a drug like this need it's be checked for example with bone mineral density and being monitored tour osteoporosis as an example.

• RAY SUAREZ:

  It's promising news for people who are coming to the end of their Tamoxifen time. Are there people who shouldn't take it? Are there women who have contraindications for Letrozole?

• DR. ANDREW VON ESCHENBACH:

  Well, I think the important thing in deciding which women should or should not go on Letrozole is to determine what their risk of recurrence might be after they have stopped Tamoxifen. That's an individual decision that has to be made with the woman's physician. But overall, for this overall population of patients, this is a very important addition to our ability to combat this horrible disease and particularly prevent the recurrences that can occur late after treatment for localized breast cancer.

• RAY SUAREZ:

  Very briefly before we go, is the way clear for Letrozole to be used in this manner? Is it approved for this kind of use after Tamoxifen?

• DR. ANDREW VON ESCHENBACH:

  This trial has just been stopped. The results are analyzed and now Letrozole will be submitted to the FDA, Food & Drug Administration, for this specific indication. However, it is available for patients with advanced breast cancer. It is already on the market and an approved drug.

• RAY SUAREZ:

  Dr. Dr. von Eschenbach, thanks a lot.

• DR. ANDREW VON ESCHENBACH:

  Thank you for having me.