There's good news for women battling a particularly difficult form of advanced breast cancer.

In a new study of patients with so-called "hormone receptor-positive" breast cancer that's spread beyond the breast, women who received a combo of two anti-estrogen drugs right away lived many months more than those who got just one drug, the researchers found.

The drugs — fulvestrant (Faslodex) and anastrozole (Arimidex) — appear to work better when given together rather than using fulvestrant as a follow-up drug given after anastrozole, according to the team led by Dr. Rita Mehta, clinical professor at the University of California, Irvine.

"These results are very exciting," said Mehta, who is also a member of the Southwest Oncology Group breast cancer research committee.

"Women who are treated with fulvestrant up front live about eight months longer. That's a lot of extra time to do the things you love with the people you love," she said in an Oregon Health & Science University news release.

"Women who received fulvestrant, right up front, lived longer based on this new long-term analysis. This is credible evidence that combination endocrine therapy should be considered an option for first-line treatment of advanced hormone receptor-positive breast cancer," Mehta said.

One breast cancer specialist who wasn't involved in the research agreed.

"Although metastatic breast cancer is not thought to be curable, it can be controlled for years and converted to a chronic disease that allows patients to carry on with their lives," explained Dr. Alice Police, who directs breast surgery at Northwell Health Cancer Institute in Sleepy Hollow, New York.

That's true for all advanced breast cancers, including the hormone receptor-positive tumors covered by this study. About two-thirds of all breast cancers are of this type, according to the American Cancer Society.

These hormone-sensitive tumors "love estrogen," Police noted, and so oncologists typically prescribe anti-estrogen drugs to help slow the disease.

"Typically, a patient is treated sequentially with different medications [such as fulvestrant and anastrozole], and switched to a different medication if their cancer spreads or grows," she explained.

But what if women got the two drugs in combination, right away?

To answer that question, Mehta's group tracked outcomes for over 700 postmenopausal women with breast cancer treated at 73 hospitals, clinics, and cancer centers across the U.S. and Canada.

The investigators found that women who received both medicines as their first line of treatment lived an average of eight months longer than those who took anastrozole alone — 50 months versus 42 months.

The study findings also showed that 42 percent of women who got the combo treatment were alive five years after their treatment, compared with 33 percent of women who got anastrozole alone.

About 45 percent of women treated with anastrozole alone were later treated with fulvestrant, when their cancer got worse or spread. But those who initially received fulvestrant had the best overall survival and progression-free survival, the researchers reported March 27 in the New England Journal of Medicine.

The study also found that patients in the combo-treatment group received lower-than-normal doses of fulvestrant in the trial: 250 milligrams (mg) per month after the first loading dose, compared with the typical 500 mg per month.

The two drugs work in slightly different ways. Anastrozole reduces the body's production of estrogen, while fulvestrant disables the tumor's ability to "feed" on circulating estrogen.