WEDNESDAY, June 2 (HealthDay News) -- For patients with early stage breast cancer, taking chemotherapy drugs sequentially over six months helps improve their survival compared to taking them at the same time over a shorter three-month span, a new study found.

The new findings will probably come as a relief to doctors, most of whom already follow the sequential protocol, said Dr. Bhuvaneswari Ramaswamy, a breast oncologist with the Ohio State University Comprehensive Cancer Center--Arthur G. James Cancer Hospital and Richard J. Solove Research Institute in Columbus.

But the "most exciting and surprising finding," said study lead author Dr. Sandra M. Swain, was that younger women who went into early menopause because of their chemotherapy -- in other words, those who stopped having periods -- were more likely to live longer.

"That's something that's not been reported," added Swain, who is medical director of the Washington Cancer Institute, Washington Hospital Center in Washington, D.C.

And this was true irrespective of whether the women's cancers were estrogen-receptor positive (meaning estrogen furthers their growth) or not.

In the study, reported in the June 3 issue of the New England Journal of Medicine, the authors tracked outcomes for almost 5,400 women with early stage breast cancer that had spread to at least one lymph node.

The patients were randomly divided into one of three treatment groups: the sequential group, which involved three drugs (doxorubicin, cyclophosphamide and docetaxel) taken in sequence over six months; or one of two "concurrent" groups, where women received either two or three of these medications concurrently for three months.

After eight years of follow-up, 83 percent of patients in the sequential group were still alive compared to 79 percent of those in the concurrent groups, the authors report.

Disease-free survival was also better in the sequential group, leading to the conclusion that a longer course of treatment remains better than a shorter course, the study said.

However, an accompanying editorial in the journal pointed out that the side effects associated with the longer program might not be worth the small survival advantage for many women.

As to the issue of amenorrhea (cessation of menstrual cycles) also improving survival, Swain said, this "really generated a new hypothesis that connects cessation of menses with survival."

No periods mean less estrogen is circulating in the body and estrogen is known to fuel certain types of cancers. But that isn't a likely explanation in this study, given that amenorrhea also resulted in longer survival even in women whose tumors were estrogen-receptor (ER) negative -- that is, their cancers don't respond to estrogen.

"This [study] gives us a hint that women who stop having their periods -- even in the patients who are not ER positive -- may have a survival advantage," said Dr. Jay Brooks, chairman of hematology/oncology at Ochsner Health System in Baton Rouge, La.

However, given that so much remains unknown, the message to women is not that suppressing ovarian function is a way to reduce their risk of breast cancer, said another study author, Dr. Charles E. Geyer Jr., director of medical affairs of the National Surgical Adjuvant Breast and Bowel Project (which conducted the trial) and vice chair of human oncology at Allegheny General Hospital in Pittsburgh.

More information

To learn more about breast cancer, visit the U.S. National Cancer Institute.