Drug combo increases progression-free survival in advanced breast cancer

Combination treatment with everolimus and the estrogen-blocker exemestane extended progression-free survival by as much as 7 months in postmenopausal women with advanced breast cancer resistant to hormone therapy, according to data from a clinical trial presented at the European Multidisciplinary Cancer Congress in Stockholm.

The phase III, randomized, double-blind, placebo-controlled, multicenter study, known as BOLERO-2 (Breast cancer trials of OraLEveROlimus-2), evaluated the efficacy of everolimus in 724 patients from 24 countries (average age 62 years) with advanced breast cancer resistant to aromatase inhibitors.

Investigators found that women with ER+HER2 advanced breast cancer treated with everolimus and exemestane had progression-free survival of 6.9 months compared with 2.8 months in women treated with exemestane alone-a 57% improvement. The trial was stopped early after a central review committee’s independent analysis found that the combination therapy extended progression-free survival by 10.6 months compared to 4.1 months for exemestane-a 64% improvement.

Everolimus targets mTOR, a protein that regulates tumor cell division, blood vessel growth, and cell metabolism. Resistance to hormonal therapy in breast cancer has been linked to overactivation of the mTOR pathway.

Side effects of the combination therapy were consistent with those reported for everolimus and didn’t worsen quality of life for patients. The most common grade 3 or 4 adverse effects reported were stomatitis, anemia, dyspnea, hyperglycemia, fatigue, noninfectious pneumonitis, and increased liver enzyme levels.

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