THURSDAY, Dec. 7, 2017 (HealthDay News) – Women with early-stage breast cancer may spend less time on hormone therapy without alleviating their prognosis, a new study suggests.
In a trial of about 3,500 patients, researchers found that seven years of hormone therapy were as effective as 10 years. At the end of the study, more than three-quarters of the women in both groups were alive and free of recurrence.
The results are "important," according to experts who attended the San Antonio Breast Cancer Symposium, where the study was published on Thursday.
"Potentially, there is a large group of patients who do not need 10 years of therapy," said Dr. Susan Domchek, of the Abramson Cancer Center at the University of Pennsylvania.
Domchek, who was not involved in the study, decisions about hormone therapy are often a source of "great discussion and distress" for patients and doctors.
Hormone therapy involves drugs that block estrogen so as not to stimulate the growth of breast cancer cells. They include tamoxifen and a group of medicines called aromatase inhibitors, such as anastrozole (Arimidex).
The problem is that medications can have difficult side effects such as bone fractures, hot flashes, sexual dysfunction, and muscle and joint pain.
"Some women have good results with medications," Domom said, "while other times they are terribly sensitive and want to share them."  So treatment decisions are always individual, he said, based on several factors, including a woman's personal likelihood of having a recurrence of breast cancer.
Dr. Erica Mayer, another cancer specialist who did not participate in the study, made the same observation.
The new findings "will ultimately offer us more options to help tailor therapy to individual patients," said Mayer, Dana senior physician. Farber Cancer Institute in Boston.
He also emphasized the big picture. "An important conclusion is that women with this disease are better than ever," said Mayer. "Most of the patients in this study were still alive and doing well."
For years, it has been standard for women with early breast cancer to continue hormone therapy for five years. The hope is to prevent the cancer from coming back.
More recently, studies have found that extending hormone therapy beyond five years can further reduce the risk of recurrence.
But it's not clear how long women should stay with that additional treatment, said Dr. Michael Gnant, the principal investigator of the new study.
To help answer the question, her team recruited nearly 3,500 women with early-stage breast cancer who underwent surgery and other standard treatments. That included five years of hormone therapy with tamoxifen, an aromatase inhibitor, or both.
Researchers randomly assigned women to two or five additional years of hormone therapy, which meant seven or 10 years in total.
In the end, the study found, the benefits in both groups were the same: an average of 14 years after its diagnosis, 78 percent of the women in both groups were alive and had no cancer recurrence.
In addition, the shorter treatment meant lower risk of bone fractures: 4 percent of women in seven years of therapy suffered a bone break, compared to 6 percent of those in the 10-year group.
The implications are clear, according to Gnant, of the Medical University of Vienna Comprehensive Cancer Center in Austria.
"Two additional years are enough," he said. "There is no reason to intensify [hormonal] adjuvant therapy beyond seven years in total, which can help reduce side effects, including fractures."
However, Domchek and Mayer did not say that.
It is still possible, he said, that certain women at high risk of recurrence could benefit from longer treatment.
For example, Domchek said, the risk of a long-term recurrence varies depending on whether the initial breast cancer had invaded nearby lymph nodes. That means that women with 10 affected lymph nodes have a higher risk than those with no affected lymph nodes.
Mayer agreed. "I do not think this study tells us we have to do one thing versus the other," he said.
Instead, he said, it offers important information for doctors and patients to use to make a "personalized" treatment plan.
The study was funded by the pharmaceutical company AstraZeneca, which makes several hormonal therapies for breast cancer.
Research presented at meetings is generally considered preliminary until peer-reviewed for publication in a medical journal.
The American Cancer Society has more about hormone therapy for breast cancer.
SOURCES: Michael Gnant, MD, director, department of surgery, Comprehensive Cancer Center, Medical University of Vienna, Austria; Susan Domchek, M.D., executive director, Basser Center for BRCA, University of Pennsylvania Abramson Cancer Center, Philadelphia; Erica Mayer, M.D., M.P.H., senior physician, Dana-Farber Cancer Institute, and assistant professor of medicine at Harvard Medical School, Boston; Presentation of December 7, 2017, San Antonio Breast Cancer Symposium, Texas