Young women treated for early hormone receptor–positive, HER2-negative breast cancer fare better if their adjuvant endocrine therapy includes ovarian function suppression (OFS), according to a new analysis published online.
Senior author Gini F. Fleming, MD, director of the medical oncology breast program at the University of Chicago Medical Center, and her colleagues analyzed data from a pair of international phase III randomized adjuvant trials: the Suppression of Ovarian Function Trial (SOFT) and the Tamoxifen and Exemestane Trial (TEXT).
Main analyses were based on a respective 240 and 145 women younger than 35 years who had undergone surgery for early hormone receptor–positive, HER2-negative early breast cancer, received chemotherapy, and were randomly assigned to 5 years of various adjuvant endocrine therapies.
In SOFT, the 5-year breast cancer–free interval was 67.1% (95% CI, 54.6%-76.9%) with tamoxifen (Nolvadex) alone, 75.9% (64.0%-84.4%) with tamoxifen plus OFS, and 83.2% (72.7%-90.0%) with exemestane (Aromasin) plus OFS (J Clin Oncol. 2017 June 27 doi: 10.1200/JCO.2016.72.0946). In TEXT, it was 79.2% (66.2%-87.7%) with tamoxifen plus OFS and 81.6% (69.8%-89.2%) with exemestane plus OFS.
In a quality of life analysis among women receiving OFS, vasomotor symptoms (hot flushes and sweats) showed greatest increase from baseline (roughly 30-40 points) in the first 6 months of therapy. Loss of sexual interest and difficulties in becoming aroused were also noteworthy (8 points or greater). However, scores for global quality of life (physical well-being, mood, coping effort, and health perception) showed little change from baseline and were essentially the same as those seen among premenopausal women aged 35 or older in the same trials.
Overall, 19.8% of the young women in SOFT and TEXT stopped all protocol-assigned endocrine therapy early. The proportion rose with time and was higher than that among the older premenopausal group.
“There was a meaningful clinical benefit in breast cancer outcomes with the addition of OFS to tamoxifen and some additional benefit from use of an aromatase inhibitor with OFS. Longer follow-up is critical to clarify potential survival benefits,” the investigators wrote. “There were substantial adverse effects from these combined endocrine treatments, but they were not different in the younger and older than 35 years populations. Despite this, rates of nonadherence were slightly higher in women younger than 35 years.
“Availability of these age-specific data regarding risks and benefits of combined endocrine therapy will support shared decision making regarding OFS among young women at high risk for recurrence and death from breast cancer and, it is hoped, improve adherence among those who select OFS,” they concluded.