Study: Drug Can Curb Breast Cancer Recurrence

A new study finds that two-thirds of women with breast cancer have a heightened risk that the cancer will recur even many years after the initial diagnosis. But the study, in the Journal of Clinical Oncology, shows the risk of cancer recurrence can be dramatically reduced by taking letrozole.

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Researchers have good news for women with the most common type of breast cancer. An already approved drug dramatically lowers the risk or recurrence, even when a woman starts taking it years after her first round of therapy?

NPR's Richard Knox reports.

RICHARD KNOX: Doctors often consider cancer cured if a patient doesn't have a recurrence for five years after treatment. But that's not true for the most common kind of breast cancer, which is fueled by estrogen.

Dr. PETER GOSS (Massachusetts General Hospital): The truth is that between year five and 15 after diagnosis, some 30 percent experience a recurrence of breast cancer.

KNOX: That's Dr. Peter Goss of Massachusetts General Hospital. He led the new study. It's published in the Journal of Clinical Oncology. It's a continuation of a big study that made a splash four years ago when the first results came out. It showed that breast cancer patients who took tamoxifen for five years and then switched to another estrogen blocker called letrozole had a much lower risk the cancer would come back.

This time, researchers looked at 1,600 women who had been on a placebo in the earlier study but decided to take letrozole after that was finished. Over five years researchers compared them to 800 women who had taken placebos earlier and elected not to take letrozole. There were two-thirds fewer breast cancer recurrences among women who took letrozole. Goss says this has big implications.

Dr. GOSS: Instead of 30 of 100 women have a recurrence, you're down to 10 or even less having a recurrence. These are very, very substantial figures by any terms in cancer therapy. They rival the best results we've had for any form of cancer therapy.

KNOX: One thing is especially striking. These women started taking letrozole anywhere from one to seven years after they stopped taking tamoxifen. Half of them didn't start letrozole for about three years. Despite the lag time, it still worked.

Dr. GOSS: Starting this medication late will still afford a lot of additional benefit in terms of reducing recurrence. And that is also a very important piece of news for younger women with breast cancer.

KNOX: For instance, a premenopausal woman with estrogen-sensitive breast cancer might want to delay taking letrozole because it causes premature menopause. The new study indicates she can wait and still get a big benefit.

Dr. Eric Weiner of Dana-Farber Cancer Institute in Boston says it's really unusual for a drug to be so effective such a long time after diagnosis.

Dr. ERIC WEINER (Dana Farber Cancer Institute): And I think it really speaks to the underlying nature and behavior of hormone receptor positive breast cancer. This is a type of malignancy that frequently is curable, but when it's destined to come back it can come back over the course of many, many years.

KNOX: Weiner is also chief scientific advisor to the breast cancer advocacy group called Susan G. Komen for the Cure. He says many American breast cancer patients are already taking letrozole after a five year course of tamoxifen because of the earlier study, but some aren't. And there are millions more in other countries who might benefit from letrozole.

Dr. WEINER: Around the world there are certainly many women who have been on tamoxifen for five years, have been off all therapy for a few years, and might consider going on a drug like letrozole or specifically letrozole based on these results.

KNOX: At least those who can afford it or have coverage for prescription drugs. Letrozole costs about $300 a month.

Richard Know, NPR News, Boston.

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