Abstract GS3-04: A prospective randomized multi-center open-label phase III trial of extending aromatase-inhibitor adjuvant therapy to 10 years - Results from 1697 postmenopausal women in the N-SAS BC 05 trial: Arimidex extended adjuvant randomized study (AERAS)

Background: Treatment with an aromatase inhibitor for 5 years as up-front monotherapy or after tamoxifen therapy for 2-3 years is the treatment of choice for hormone-receptor-positive breast cancer in postmenopausal women. Extending treatment with an aromatase inhibitor to 10 years may reduce the risk of breast cancer recurrence. Methods: We conducted a prospective randomized multi-center open-label phase III trial to assess the effect of the extended use of anastrozole for an additional 5 years. Postmenopausal patients with stageI-III, hormone-receptor-positive breast cancer, disease-free after 5 years of either anastrozole alone or tamoxifen 2-3 years followed by anastrozole 3-2 years were randomized to continual group with anastrozole for an additional 5 years or stop group without an additional anastrozole. Our primary end point was disease-free survival. Results: We enrolled 1697 women. After a median follow up of 4.9 years, there were 149 events involving disease recurrence or the occurrence of contralateral breast cancer (51 in continual group and 98 in stop group) and 7 deaths (3 in continual group and 4 in stop group). The 5-year disease-free survival rate was 91.9% (95% confidence interval [CI], 89.4 to 93.8) in continual group and 84.4% (95% CI: 80.0 to 88.0) in stop group (hazard ratio for disease-free survival,0.548 ;P=0.0004. by a two-sided log-rank test stratified according to nodal status, prior adjuvant chemotherapy, institution, and choice of anastrozole or tamoxifen). The rate of 5-year overall survival was 99.5% in continual group and 99.6% in stop group. (hazard ratio,1.389 ;P=0.665). The rate of 5-year distant disease-free survival was 97.2% in continual group and 94.3% in stop group (hazard ratio,0.514 ;P=0.0077). Bone-related adverse events were observed more frequently among patients in continual group than among patients in stop group, including a higher incidence of bone pain, stiff joints, bone fractures, and new-onset osteoporosis. Conclusion: The extension of treatment with an adjuvant aromatase inhibitor (anastrozole) to 10 years resulted in significantly higher rates of disease-free survival and distant disease-free survival than those with no additional anastrozole, but the rate of overall survival was not different between two groups. Our study shows that it is safe and beneficial for postmenopausal patients with hormone-receptor-positive breast cancer to take an anastrozole as adjuvant therapy for an additional 5 years after initial treatment. (UMIN:000000818) Citation Format: Ohtani S, Iijima K, Higaki K, Sato Y, Hozumi Y, Hasegawa Y, Takei H, Tanaka M, Yagata H, Masuoka H, Tanabe M, Egawa C, Komoike Y, Saji S, Nakamura T, Yanagita Y, Ohtsu H, Mukai H, Iwase T. A prospective randomized multi-center open-label phase III trial of extending aromatase-inhibitor adjuvant therapy to 10 years - Results from 1697 postmenopausal women in the N-SAS BC 05 trial: Arimidex extended adjuvant randomized study (AERAS) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr GS3-04.