Letrozole has proven benefit for breast cancer

Reported by Susan Aldridge, PhD, medical journalist

A new study shows that women treated with letrozole have reduced recurrence of breast cancer.
Letrozole is a new type of drug called an aromatase inhibitor. It suppresses the production of estrogen which, otherwise, may stimulate the growth of a breast cancer. Its action is broadly similar to that of tamoxifen, which is widely used to prevent recurrence of breast cancer.

However, tamoxifen is known to lose its effectiveness after five years of treatment - probably because cells become resistant to it. A team at the National Cancer Institute of Canada now report on how letrozole can help women with breast cancer who have previously been on tamoxifen. More than 5,000 women who had been on tamoxifen for five years received either letrozole or placebo for another five years. Four years after the start of the trial, it was already clear that women on letrozole were significantly less likely to have a recurrence of breast cancer than those on placebo. Therefore the trial was stopped and now the final data are available, showing a five per cent reduction in recurrence on letrozole compared to placebo. Those on the drug also had a 39 per cent reduction in the risk of metastasis. Overall survival was not different between letrozole and placebo, but those whose tumors had spread and those on tamoxifen for more than five years had a clear survival advantage on letrozole. Further research is now needed to see how long treatment on aromatase inhibitors should continue and whether they can benefit those who have not previously been on tamoxifen.

Source
Journal of the National Cancer Institute 7th September 2005