The study reviewed here found that taking the aromatase inhibitor Femara (chemical name: letrozole) after taking tamoxifen for 5 years reduced the risk of the breast cancer coming back (recurrence), compared to not taking Femara after tamoxifen. These results were significant, which means they likely happened because of the Femara and not just by chance.
The risk of the cancer coming back was lowered by 63% in women who started taking Femara up to 7 years after finishing 5 years of tamoxifen. The women took Femara for 5 years.
Hormonal therapy, with either tamoxifen or an aromatase inhibitor, is usually taken for 5 years after surgery (and possibly radiation and chemotherapy) to lower the risk of hormone-receptor-positive early-stage cancer coming back in post-menopausal women. But the risk of the breast cancer coming back doesn't end after these 5 years of hormonal therapy. (This 5-year schedule was created because taking tamoxifen longer than 5 years doesn't offer any additional benefits.)
Tamoxifen works by blocking the effects of estrogen on breast cancer cells. Aromatase inhibitors help stop breast cancer from coming back by preventing the formation of estrogen. Because these two types of hormonal therapy medicines work differently, researchers wondered if taking aromatase inhibitors after 5 years of tamoxifen, for a total of 10 years of hormonal therapy, would offer additional risk reduction benefits. This study confirms earlier results showing that 10 years of hormonal therapy, first with tamoxifen, then with an aromatase inhibitor, continues to reduce the risk of the cancer coming back.
About 5% of the women who took only tamoxifen for 5 years had the cancer come back during the 3 years after the research ended. Only 2% percent of the women who took tamoxifen for 5 years and then took Femara for 5 years (for a total of 10 years of hormonal therapy) had the cancer come back.
When this study was started, tamoxifen was the hormonal therapy used to reduce the risk of hormone-receptor-positive early-stage breast cancer coming back in post-menopausal women. Since that time, aromatase inhibitors have been found to work a little better than tamoxifen to reduce the risk of recurrence. Besides Femara, there are two other aromatase inhibitors: Arimidex (chemical name: anastrozole) and Aromasin (chemical name: exemestane).
This study looked at Femara, but it's likely that all of the aromatase inhibitors can reduce the risk of the cancer coming back when taken after 5 years of tamoxifen.
If you're finishing 5 years of tamoxifen, talk to your doctor about the pros and cons of taking an aromatase inhibitor for another 5 years to continue to reduce your risk of the cancer coming back. Together, you and your doctor can decide on an approach that is right for YOU and your unique situation.
CHICAGO (Reuters) - Taking the breast cancer pill Femara can significantly reduce the chances that a woman's cancer will return, even long after she has stopped taking the estrogen blocker tamoxifen, U.S. researchers said on Monday.
They said post-menopausal women who took the Novartis AG drug Femara anywhere from one to seven years after finishing a five-year regimen of tamoxifen reduced the risk the cancer would come back by 63 percent.
"What our results have shown for the first time in breast cancer treatment history is that taking an anti-estrogen anywhere along that line appears to have a dramatic reduction in the risk of recurrence," said Dr. Paul Goss of Massachusetts General Hospital, whose study appears in the Journal of Clinical Oncology.
The drug, known generically as letrozole, cut the risk of cancer spreading to other areas of the body by 61 percent, and cut the risk that a tumor would develop in the unaffected breast by more than 80 percent.
Letrozole belongs to a new class of breast cancer drugs known as aromatase inhibitors, which block the production of estrogen that can lead to cancer. It is recommended for use in women past menopause.
The most widely used estrogen-blocking drug is tamoxifen, which was shown to cut the risk of cancer recurrence by close to 50 percent. But benefits of the pill, sold by AstraZeneca under the brand Nolvadex and also sold generically, fall significantly after five years.
Tamoxifen also raises the risk of death from strokes and endometrial cancer.
But more than half of breast cancer recurrences and deaths occur five or more years after completing tamoxifen.
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"What is important for doctors and patients to recognize unfortunately is that the risk of recurrence of this type of breast cancer does not end at five years," Goss said in a telephone interview.
"The risk continues and the benefit remains substantial of starting late on therapy," Goss said.
Goss' findings are based on an analysis of 1,579 women who decided to switch to letrozole from a placebo after the trial was halted. Their results were compared to about 800 women who stayed on the placebo.
Almost three years after the study ended, those who began letrozole had only a 2 percent risk of tumor recurrence, compared with almost 5 percent in those choosing no treatment.
Goss said the findings were limited by the fact that women made the decision about whether they would take the drug or not. Nevertheless, he said the findings are strong and likely to change how women with breast cancer are treated.
"The risk that hormone-dependent breast cancer will recur continues indefinitely, and our results imply that aromatase inhibition is effective whenever initiated," said Goss, who is also a professor at Harvard Medical School.
He said the study looked at the effects of letrozole only, but said the results will likely apply to all aromatase inhibitors. Pfizer Inc makes an aromatase inhibitor called exemestane, which it sells under the brand Aromasin, and AstraZeneca Plc makes anastrozole, sold under the brand Arimidex.
Another study in the journal showed that taking another exemestane soon after completing tamoxifen treatment reduced the risk of recurrence by 56 percent.
Breast cancer is the second-leading cause of cancer death among U.S. women after lung cancer. It kills 500,000 people globally every year.
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