Breast Cancer Drug Good Later Than Thought

Researchers have found that women who've taken the breast cancer drug Tamoxifen can benefit by following it up with another drug, Femara -- even if they start that second drug years later.

It had been thought for a long time that Femara is only useful when begun almost immediately after the patient stops using another Tamoxifen. But this research shows that even women who didn't start Femara right away can still benefit from starting it, even years later.

On The Early Show Tuesday, medical contributor Dr. Sean Kenniff called it
great news.

Tamoxifen, he says, is a lifesaver. It reduces breast cancer recurrence by shielding breast cells from the harmful effects of the hormone estrogen. But since benefits are often more limited after five years, and the risk of some negative side effects tends to increase at that point, patients are commonly taken off Tamoxifen.

Then, they might be switched to another class of breast cancer drugs called aromatase inhibitors, which work by decreasing the body's actual production of estrogen.

This study, which appears in the Journal of Clinical Oncology, looked at one particular aromatase inhibitor called Femara, also known as Letrozole.

Until now, Kenniff explained, we thought it had to be given within three months of stopping Tamoxifen. In fact, the Food and Drug Administration approved it only for within that three-month window.

This study found that women who waited much longer to start Femara, even up to seven years, still benefited greatly from taking it.

The three month, he says, is somewhat arbitrary. It happens to have been the timeframe chosen by the researchers for the original studies on Femara. They thought, at the time, that using it soon after Tamoxifen would provide the biggest one-two punch against any remaining cancer cells.

But cancer cells now appear to have the potential to lie dormant longer than previously thought, and this study suggests it's never too late to start therapies like Femara as a preventive measure.

As for specifics from the study:

Women who began Femara beyond that three-month window cut the risk of breast cancer recurrence by almost 60 percent, from nearly 5 percent to 2 percent. The risk of DEATH from breast cancer was cut in half. The spread of cancer -- called metastasis -- was reduced by 61 percent. And new cancer in the other breast was reduced by 82 percent. So, it appears the drug still had a substantial benefit, even when it was started long after Tamoxifen was stopped.

Doctors aren't sure if this study applied only to Femara, Kenniff says. There are other drugs in the aromatase inhibitor family, such as Aromasin and Arimidex. It's possible they all provide similar protection for women with breast cancer. But Femara was the only drug studied here, so we don't know that similar conclusions can be drawn about the other drugs.

The study doesn't apply to all women with breast cancer, Kenniff stressed. Women in the study were post-menopausal. They all had early-stage breast cancer. And their tumors were all hormone-receptor positive. That's a large portion of women with breast cancer, but still not everyone. Plus, this wasn't a randomized, double-blind study. The patients actually chose their treatment. That could result in some statistical inaccuracy.

But overall, this is still very promising, Kenniff says, and well-worth discussing with your doctor if you're a breast cancer survivor.