These data were presented during the "Best of Oncology" session in this year’s annual meeting of the American Society of Clinical Oncology (ASCO).
Distant metastases are a well-established risk factor for breast cancer death.
The international, double-blind, randomized, multi-center trial involved post-menopausal women who have completed five years of tamoxifen and were given letrozole for another five years in the so-called extended adjuvant treatment.
At 2.5 years of follow-up, a survival advantage has now become apparent in those women whose cancer had spread to lymph nodes at the time of diagnosis (node-positive).
In this group of trial participants, which comprised about 50 percent of the total number of patients, deaths were reduced to a significant 39 percent versus dummy pills.
These results from the trial indicated that letrozole is the first hormonal therapy to demonstrate a survival advantage in the extended adjuvant setting.
"Overall, the results of the study may provide a new option for post-menopausal women completing standard adjuvant treatment with tamoxifen," said Dr. Paul Goss, director of breast cancer prevention and research at Princess Margaret Hospital in Toronto, Canada.
"Treatment with letrozole resulted in a marked reduction in the risk of recurrent breast cancer and the occurrence of new breast cancer. Most importantly, treatment with letrozole also reduced distant metastases, which are very often fatal," Goss said.
Letrozole, an aromatase inhibitor, is an oral once-a-day, first-line treatment for post-menopausal women with hormone receptor positive or hormone receptor unknown locally advanced or metastatic breast cancer.
It is also approved for the treatment of advanced breast cancer in post-menopausal women with disease progression following antiestrogen therapy, and as neo-adjuvant (pre-operative) therapy.
For more information on breast cancer and letrozole, patients are advised to consult a doctor.