Reducing ovarian function yields better outcomes for young women with breast cancer | ASCO 2023

Background

Estrogen drives cancer growth in some breast cancers. Stopping or reducing estrogen has become an important, but not new, part of cancer treatment. Ovarian function suppression (OFS) has been used in some form to treat breast cancer since the late 1800s.

Estrogen receptor-positive breast cancer is the most common form of breast cancer. Many early-stage, estrogen receptor-positive breast cancers respond well to treatments such as hormonal therapy. Yet, for some, the cancer will return more aggressively, sometimes many years later. Doctors look for clues to better understand why and when cancer returns and to develop treatments to reduce the risk of recurrence.

Results

Ovarian ablation or suppression reduces the risk of breast cancer recurrence significantly. This meta-analysis of years of research yielded very consistent findings. People who had their ovarian function suppressed were much less likely to have had cancer come back 15 years later.

The research team looked at data from nearly 15,000 women who participated in 23 clinical trials between 1948 and 2009. All had estrogen receptor-positive breast cancer or a risk of breast cancer recurrence. The goal was to look at the long-term impact of ovarian ablation or suppression—lowering or stopping estrogen production. In the older trials, ablation was achieved through surgery or radiation. In more recent trials, suppression was usually achieved using medications called gonadotropin releasing hormone (GnRH) agonists.

Confirming premenopausal status was important for this study. The researchers looked at chemotherapy use to help identify premenopausal women because chemotherapy can cause early menopause. They divided participants into two study groups. The first group included participants who did not have chemotherapy and those who were confirmed premenopausal after chemotherapy. People whose menopausal status was unknown after chemotherapy made up a second study group.

Key results reported include:

• The no-chemotherapy/premenopausal group saw much greater benefit from ovarian ablation or suppression than the group whose menopausal status was unknown (29% reduction in recurrence versus a very minimal but still significant difference).
• The no-chemotherapy/premenopausal group had a 30% reduction in breast cancer deaths after 20 years of follow-up. Death from any cause was reduced by 25% with ovarian ablation or suppression.
• Women who also took tamoxifen did not see as strong a benefit from ovarian ablation or suppression. They had a 4.5% reduction in recurrence. Women who did not take tamoxifen saw a 17.5% reduction in recurrence with ovarian ablation or suppression. The study author attributed this difference to tamoxifen providing some of the same value as ovarian ablation or suppression. He added, however, that the benefit of ablation or suppression may be longer lasting.

Grouping participants by age did not reveal any differences among age groups. Likewise, the benefit was similar for people, regardless of whether they had cancer in the lymph nodes.

What does this mean for you?

This study provides strong evidence in support of ovarian ablation or suppression for premenopausal women diagnosed with breast cancer. Importantly, ovarian ablation or suppression did not increase other health risks. Participants in the study were not more likely to die from other causes.

The expert who discussed this study, as well as two other studies related to young women with breast cancer, emphasized the importance of “individual decision making and tailored approaches.” Talk with your doctor about your situation and the treatment plan that would be best for you.