The Early Show medical correspondent Emily Senay explains the drug called letrozole, which is marketed as femara, is in a class of drugs known as aromatase inhibitors. These are drugs that suppress the female hormone estrogen, which is thought to fuel some types of breast cancer.
Senay says there has been a lot of success with these drugs in recent years. Letrozole is in the same family as tamoxifen, which is the current gold standard treatment used to prevent breast cancer from recurring following surgery.
Tamoxifen has been proven to cut the risk of recurrence of breast cancer by about 30 percent, but it can only be taken for five years.
The letrozole trial found that the drug helps after tamoxifen's benefits run out. A study published by the New England Journal of Medicine followed 5,000 women for an average of two and a half years.
Researchers found that letrozole dramatically reduced the risk of breast cancer recurring by 43 percent, and it cut the death rate from breast cancer by almost 50 percent. The researchers said the benefit was substantially greater than expected.
Senay says the news was so good that researchers halted the trial early so that women who were getting the placebo could start taking letrozole to get the benefit, too.
Like tamoxifen, letrozole is for women whose breast cancer is fueled by estrogen and diagnosed and treated early on. Tamoxifen is the proven first line of defense after surgery, says Senay, but since it can only be taken for five years, the hope is that letrozole can be used after tamoxifen to help ward off breast cancer in the period beyond five years when recurrence is still a big risk.
The drug's side effects included hot flashes, arthritis and body aches.
Senay warns that some important questions still need to be answered. She says it's not clear how long women who take letrozole should take it, and the long-term effects of the drug are not yet known. For example, data on effects of letrozole on bone density, cardiovascular health and quality of life collected as part of this trial haven't been reported yet.