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.
To learn more about breast cancer, visit the U.S. National Cancer Institute.
SOURCES: Bhuvaneswari Ramaswamy, M.D., breast oncologist, Ohio State University Comprehen
All rights reserved