SAN ANTONIO – Extending treatment with adjuvant anastrozole (Arimidex) to 10 years led to significantly higher rates of disease-free and distant disease-free survival in postmenopausal women with hormone receptor–positive breast cancer in the prospective, randomized, open-label phase 3 Arimidex Extended Adjuvant Randomized Study (AERAS).
After a median of 4.9 years of follow-up, the primary endpoint of disease-free survival (DFS) was 91.9% in 840 women who were randomized to continue receiving anastrozole for an additional 5 years versus 84.4% in 843 who stopped after the initial 5 years (hazard ratio, 0.548; P = .0004), Shoichiro Ohtani, MD, reported at the San Antonio Breast Cancer Symposium.
The rate of 5-year distant DFS was 97.2% vs. 94.3% in the groups, respectively (HR, 0.514; P = .0077), said Dr. Ohtani, of Hiroshima City (Japan) Hiroshima Citizens Hospital.
“As we expected, there was no difference between the two groups in overall survival,” he said; overall survival was 99.5% and 99.6% in the groups, respectively (HR, 1.389; P = .665).
Study subjects were postmenopausal patients with stages I-III hormone receptor-positive breast cancer (HR+ BC) with a median age of 64 years who were disease-free after 5 years of either anastrozole alone or tamoxifen for 2-3 years followed by anastrozole 2-3 years. They were enrolled between November 2007 and November 2012.
Treatment with an aromatase inhibitor such as anastrozole for up to 5 years either as up-front monotherapy or after 2-3 years of tamoxifen therapy is the treatment of choice for HR+ BC in postmenopausal women, but it was thought that extending aromatase inhibitor therapy to 10 years might reduce the risk of breast cancer recurrence, Dr. Ohtani explained.
Indeed, while women randomized to extended anastrozole treatment in the current study experienced more bone-related adverse events, including arthralgia (19.2% vs. 11.7%), stiff joints (11.7% vs. 4.9%), bone fractures (2.8% vs. 1.1%), and new-onset osteoporosis (33% vs. 28%) than did those in the group that stopped anastrozole at 5 years, extended treatment significantly reduced recurrence rates.
The findings show that extended adjuvant anastrozole treatment for an additional 5 years after initial treatment is safe and provides important DFS and distant DFS benefits, he concluded.
Dr. Ohtani has received speaker fees from CHUGAI, Astra Zeneca, Novartis,and Ezai.
SOURCE: Ohtani S et al. SABCS 2018, Abstract GS3-04.