A current breast cancer treatment offers more benefits for some women who take it for 10 years instead of 5 years.

Women who took letrozole for an extra five years had a 34 percent lower risk of recurrence than those who received the placebo.

Results of a randomized clinical trial found that postmenopausal women who discovered their breast cancer early had a lower chance of the cancer returning when they extended their anti-estrogen hormone therapy. The study was reported over the weekend at the American Society of Clinical Oncology meeting.

Aromatase inhibitors such as Arimidex (anastrozole), Aromasin (exemestane), and Femara (letrozole) are used to stop production of estrogen in women.

In the study on 1,918 postmenopausal women with hormone-receptor positive breast cancer, 959 women took letrozole and 959 received a placebo. Of those who took the drug, 13 developed breast cancer in the opposite breast and 55 had a recurrence in the same breast, compared to 31 on the placebo who got cancer in the opposite breast and 68 who experienced recurrence. The women had previously taken an aromatase inhibitor for at least five years, or had taken it after treating their cancer with Nolvadex (tamoxifen), another treatment.

Women who took letrozole for the extra five years had a 34 percent lower risk of recurrence than those who received the placebo.

“Women with early-stage hormone receptor-positive breast cancer face an indefinite risk of relapse,” said Dr. Paul Goss, lead study author and breast cancer researcher at Massachusetts General Hospital, in a statement.

He said that prolonging aromatase inhibitor therapy can further reduce the risk of breast cancer recurrences.

Related: Real Answers on Cancer, Finally?

“Longer aromatase inhibitor therapy also showed a substantial breast cancer preventative effect in the opposite, healthy breast,” Goss added.

Who do you think would win the Presidency?

By completing the poll, you agree to receive emails from LifeZette, occasional offers from our partners and that you've read and agree to our privacy policy and legal statement.

New Standard?
So is 10 years the new standard treatment time as a result of this study? Dr. Charles Shapiro, an oncologist at Mount Sinai Hospital in New York City, said the practice should change — but he said prescribing the drug for 10 years shouldn’t be a new standard of care because it’s not always helpful.

Prescribing the drug for 10 years shouldn’t be a new standard of care because it’s not always helpful, said one oncologist.

“For many women, the benefits of extended aromatase inhibitors to 10 [years] will be worthwhile and outweigh the side effects — but for not for all,” he said, noting that the risk of recurrence between 5 and 10 years is higher for those with axillary node-positive breast cancer and those with larger tumors.

Extended therapy can cause increased fractures — something already shown — so doctors and patients have to balance the cancer and bone health risks. He recommends extending aromatase inhibitor duration except in those with smaller, low-grade tumors and node-negative tumors.

“Osteoporosis and fractures are largely preventable if screened for bone density and treatment is initiated when appropriate,” Shapiro told LifeZette.