SAN ANTONIO – The progression-free survival (PFS) benefit seen with everolimus plus exemestane over exemestane alone at 7.5 months and 12.5 months in women with advanced breast cancer is maintained at 18- month follow-up, investigators announced at the San Antonio Breast Cancer Symposium (SABCS).

Martine Piccart, MD, Director of Medicine at the Jules Bordet Institute in Brussels (Belgium), and colleagues elsewhere presented the final PFS results after 18 months’ median follow-up in 724 women enrolled in the phase III Breast Cancer Trials of Oral Everolimus (BOLERO)-2.

BOLERO-2 evaluated the efficacy and safety of the combination of the oral mammalian target of rapamycin (mTOR) inhibitor everolimus (10 mg once daily) and the steroidal aromatase inhibitor exemestane (25 mg once daily) versus placebo plus exemestane in postmenopausal women with hormone receptor-positive advanced breast cancer progressing or recurring after nonsteroidal aromatase inhibitor therapy.

“Endocrine therapy is the backbone of treatment for women with hormone receptor-positive advanced breast cancer,” Dr. Piccart explained. “However, de novo or acquired resistance to endocrine therapy can occur, and treatment options for such women have been limited.”

The primary study endpoint was progression-free survival (PFS).

At a median follow-up of 18 months, 510 PFS events were reported.

The combination of everolimus plus exemestane produced significant durable PFS benefits by local assessment (median of 7.8 months for everolimus plus exemestane versus 3.2 months for exemestane alone (HR=0.45; P

Fewer deaths occurred with the everolimus/exemestane combination than with exemestane alone (25.4% versus 32.2%).

Adverse events seen with everolimus plus exemestane were consistent with those reported with everolimus in earlier studies.

Dr. Piccart said that the results support the rationale of targeting the mTOR pathway to improve clinical outcome in patients with HR-positive advanced breast cancer progressing after nonsteroidal aromatase inhibitor therapy.

By Jill Stein
Jill Stein is a Paris-based freelance medical writer.