Letrozole Increases Survival Rate in Node-Positive Breast Cancer

Peggy Peck

June 10, 2004

June 10, 2004 (New Orleans) — Updated survival data from the landmark MA-17 trial indicate that the aromatase inhibitor letrozole can further reduce the risk of death by 39% in women with node-positive breast cancer.

"A survival advantage has now become apparent in those women whose cancer had already spread to their lymph nodes at the time of diagnosis," said Paul Goss, MD, director of Breast Cancer Prevention and Research at Princess Margaret Hospital in Toronto, Ontario, Canada.

Dr. Goss presented the updated data from the MA-17 trial at a special "Best of Oncology" symposium at the 40th annual meeting of the American Society of Clinical Oncology. The results of that trial were announced in Toronto in October 2003 after the study was stopped prematurely when the data safety monitoring board determined that letrozole demonstrated a significant benefit compared with placebo.

Patients in the MA-17 study, which was initiated by the investigators and supported by Novartis Oncology, had undergone definitive breast cancer treatment at diagnosis and then had been maintained on tamoxifen for five years. After that the women were randomly assigned to either letrozole therapy or placebo for an intended five-year period.

Dr. Goss said that when the trial was stopped prematurely, considerable data were still being accrued. The more mature data indicated a 39% reduction in mortality compared with placebo in postmenopausal women with early breast cancer. That reduction achieved statistical significance (P = .035), he said.

In women with either node-positive or node-negative breast cancer, there were 18% fewer deaths among the women who were taking letrozole, but that did not reach statistical significance. Letrozole was also associated with a 40% reduction in the risk of distant metastases and a 43% reduction in risk of recurrence and local recurrence.

"Overall, the results of MA-17 may provide a new option for postmenopausal women completing standard adjuvant treatment with tamoxifen," Dr. Goss said.

"It is always good to have new options in treating women with breast cancer," said Andrew Seidman, MD, associate attending physician for breast cancer service at Memorial Sloan-Kettering Cancer Center in New York City. He told Medscape that the results of MA-17 "already changed the way we treat breast cancer," but he said the updated data confirm the benefit of aromatase inhibitors.

"All the data point in the same direction," he said. Dr. Seidman was not involved in the study.

Even with the new data, Dr. Seidman said that clinicians still have to carefully evaluate each patient to determine if the patient will be better off with tamoxifen or an aromatase inhibitor because of the different side effect profiles.

In addition, clinicians will have to determine timing and sequence of use of the different agents. For example, Dr. Seidman noted that many women may be given tamoxifen for five years, followed by letrozole for five years, as in MA-17. "But in other women, the decision may be 2.5 years of tamoxifen and 2.5 of an aromatase inhibitor," which was the design of IES. He noted that he and other clinicians are also offering some women an aromatase inhibitor without tamoxifen, which was the design of the ATAC trial. Until results from additional trials are released, the optimal regimen and sequence will remain unknown.

ASCO 2004 Annual Meeting: Best of Oncology symposium. Presented June 8, 2004.

Reviewed by Gary D. Vogin, MD

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