Adding 2 years of ovarian function suppression (OFS) to the standard 5-year regimen of tamoxifen could improve disease-free and overall survival in women with estrogen receptor–positive breast cancer who have been previously treated with chemotherapy and definitive surgery, according to results from the phase 3 ASTRRA trial.
The findings add support to recent results from the similarly designed Suppression of Ovarian Function Trial (SOFT), reported Hyun-Ah Kim, MD, PhD, of Korea Cancer Center Hospital, Seoul, and colleagues.
“Although OFS in breast cancer has been studied for decades and has been used widely in clinical practice, evidence for the benefits of adding OFS to standard adjuvant tamoxifen treatment is insufficient,” the investigators wrote in the Journal of Clinical Oncology.
The ASTRRA trial enrolled 1,483 premenopausal women aged 45 years or younger with estrogen receptor–positive breast cancer who had been previously treated with chemotherapy and definitive surgery. Of those, 1,293 women were randomized to receive either 5 years of tamoxifen, or the same regimen plus 2 years of OFS, at 35 treatment centers in South Korea. In all, 1,282 women were eligible for analysis.
The primary endpoint was disease-free survival, defined as secondary malignancy, invasive contralateral breast cancer, invasive local recurrence, regional recurrence, distant recurrence, or death from any cause. The secondary endpoint was overall survival.
After a median follow-up of 63 months, women who received OFS in addition to tamoxifen had an estimated disease-free survival rate of 91.1%, compared with 87.5% in those who received tamoxifen alone (P = .033). Similarly, adding OFS was associated with a better estimated 5-year overall survival rate, compared with standard monotherapy (99.4% vs. 97.8%; P = .029), Dr. Kim and associates said.
Despite having a shorter follow-up and smaller population size, the results from ASTRRA were similar to those from SOFT, most likely because ASTRRA patients had higher-risk disease, the investigators noted.
“The results of ASTRRA confirm the findings of SOFT, that the addition of OFS to tamoxifen provides survival benefits for women [who are] at sufficient risk for recurrence to receive adjuvant chemotherapy and who remain in a premenopausal state after chemotherapy,” they concluded.
The study was primarily funded by AstraZeneca, with additional support from the Korea Institute of Radiological and Medical Sciences. The investigators disclosed relationships with Novartis, Roche, Amgen, and others.
SOURCE: Kim HA et al. J Clin Oncol. 2019 Sep 16. doi: 10. 1200/JCO.19.00126.