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New drug announced for long-term breast cancer treatment
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Dr. James Ingle of Mayo Clinic was the lead U.S. researcher on the study of a new breast cancer drug. The drug, called letrozole, has proven effective in preventing cancer from reoccuring. The study was halted early because of the dramatic results. (Photo courtesy of Mayo Clinic)
Cancer researchers announced a major treatment advance for breast cancer survivors Thursday. They've found an estrogen-blocking drug, which greatly reduces the reoccurrence of breast cancer. Canadian oncologists led the breakthrough study, and a Mayo physician conducted research in the U.S.

Rochester, Minn. — The announcement offers an important new option for breast cancer survivors who have been cancer-free for five years.

Rochester resident Lois Sterling is a typical case. She was diagnosed with breast cancer in 1995. She underwent a lumpectomy followed by radiation treatment. Once that was complete, Sterling's oncologist put her on the drug tamoxifen.

"When you were on tamoxifen you felt ... 'We're going to take care of any cells that might be malignant that weren't reached by the radiation.'" And so it felt like I was OK," says Sterling. "But then when the tamoxifen ended it was like, now what?"

Tamoxifen is considered effective for about five years. After that it stops blocking the production of estrogen. When estrogen levels get out of control, cancer is more likely to reoccur.

Before, patients like Sterling and their physicians didn't have many choices after tamoxifen. Now, according to a new study, once tamoxifen runs its course, there's a drug that can take its place.

This means to me that I have a treatment to talk about with my patients, whereas I had nothing to talk with them about before.
- Dr. James Ingle, Mayo Clinic

The drug is called letrozole. In the past it's been successfully used to treat patients with advanced cancer. But in research involving more than 5,000 women from nine countries, the drug was found to be effective in warding off the disease.

Mayo medical oncologist James Ingle coordinated the U.S. arm of the study. He says participants were given either a placebo or letrozole.

"What was identified was an extreme result. This was part of an early analysis of the study, and it found that there was a significantly higher risk of reoccurrence of the breast cancer in women that took the placebo than those who got the letrozole," says Ingle.

More precisely, women who took letrozole were 43 percent less likely to redevelop breast cancer. Those results were so promising, the Data Safety Board halted the study. The board is in charge of monitoring research. It recommended women on the placebos be given the option to take letrozole.

Oncologist Lawrence Wickerham treats cancer patients in Pennsylvania. He also helps organize cancer research trials across the country. He says the study results are good news, but he says there are still a lot questions left unanswered.

"While we know it works, we're not quite sure what the maximum duration of the therapy should be. And we have not yet been able to quantify all of the long-term side effects and toxicity of this drug," says Wickerham.

One big concern is osteoporosis. Estrogen-blocking drugs contributed to bone loss, and researchers urge physicians to carefully monitor patients taking letrozole for symptoms. The drug can only be prescribed for post-menopausal woman, and for patients whose tumors contained a certain estrogen-progesterone level.

But Mayo's James Ingle says for the majority of women who developed and were treated for breast cancer, the drug has potential.

"This means to me that I have a treatment to talk about with my patients, whereas I had nothing to talk with them about before," says Ingle.

Rochester cancer survivor Lois Sterling plans to talk with her physician about taking the drug. She hopes it will give her more peace of mind for years to come.

The international study, led by Canadian researchers with help from the Mayo Clinic and physicians around the world, is published online in the New England Journal of Medicine. The study will appear in print in next month's edition of the journal.

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