Everolimus in combination with exemestane has shown promise for the treatment of breast cancer.

"For postmenopausal patients with hormone receptor (HR)-positive metastatic breast cancer, the addition of everolimus to exemestane markedly improves the duration of disease control," said Gabriel N. Hortobagyi, M.D., FACP, professor of medicine, chair of the department of breast medical oncology and director of the Multidisciplinary Breast Cancer Research Program at the University of Texas MD Anderson Cancer Center in Houston.

Hortobagyi presented findings from Breast Cancer Trials of Oral Everolimus (BOLERO-2), a phase 3 clinical trial, at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium, held Dec. 6-10, 2011.

BOLERO-2 researchers enrolled 724 postmenopausal patients with HR-positive metastatic breast cancer and evidence of progressive disease while receiving anastrozole or letrozole. They randomly assigned patients to treatment with exemestane plus everolimus or with exemestane plus placebo.

Results revealed a median progression-free interval of 3.2 months for 239 patients treated with exemestane plus placebo. Among the 485 patients treated with exemestane plus everolimus, researchers found a median progression-free interval of 7.4 months, "a highly significant difference," Hortobagyi said.

Clinical benefit rates, which include complete response, partial response, or stable disease exceeding six months, were 25.5 percent among patients treated with exemestane and placebo and 50.5 percent among those treated with exemestane and everolimus.

"The original hypothesis predicted this increased benefit from the combination, based on compelling preclinical experiments and preliminary results from earlier, smaller clinical trials. These results establish a new standard of care for this group of patients," Hortobagyi said.

He continued, "These results highlight the progress being made in understanding the evolving mechanisms of resistance to standard therapies."

Researchers were not yet able to measure survival analysis in BOLERO-2. However, treatment was well tolerated, with oral mucositis, fatigue, pneumonitis and hyperglycemia being the most common side effects.