A phase III multicenter study of eribulin mesylate in women with previously treated metastatic breast cancer failed to meet its co-primary endpoints of improved progression-free survival and overall survival compared with capecitabine, according to data presented at the 2012 CTRC-AACR San Antonio Breast Cancer Symposium.

“The study did not show a statistically significant benefit of eribulin over capecitabine, and it did not show a benefit in terms of progression-free survival, so the overall study objectives were not met,” said Peter A. Kaufman, M.D., associate professor of medicine at the Geisel School of Medicine at Dartmouth and the Norris Cotton Cancer Center in Lebanon, N.H.

“However, this is the first study demonstrating that eribulin is active in the first-, second and third-line setting in metastatic breast cancer,” Kaufman said.

“Although we didn’t show a statistically significant superiority over capecitabine, which was our goal, numerically the overall survival with eribulin was better than with capecitabine.”

In 2010, the FDA approved eribulin for the treatment of patients with metastatic breast cancer who had previously received an anthracycline and a taxane and at least two cytotoxic chemotherapy treatment regimens for metastatic breast cancer. The FDA granted approval based on data showing a statistically significant improvement in overall survival compared with current treatments.

Kaufman and colleagues examined whether eribulin would be effective as an earlier-line treatment in women with metastatic breast cancer. They randomly assigned 1,102 patients to eribulin or capecitabine. Patients had all received prior anthracycline- and taxane-based therapy and received the study drug as the first, second or third line of therapy for metastatic disease.

The median overall survival for patients assigned to eribulin was 15.9 months compared with 14.5 months for patients assigned to capecitabine. Median progression-free survival was 4.1 months for eribulin and 4.2 months for capecitabine.

Exploratory analyses of patient subsets showed that the median overall survival in women with HER2-negative breast cancer was 15.9 months with eribulin compared with 13.5 months with capecitabine. In women with triple-negative breast cancer, which is a particularly aggressive subset, the median overall survival was 14.4 months with eribulin compared with 9.4 months with capecitabine.

Kaufman and colleagues are still compiling data from the quality-of-life analysis, which according to Kaufman, will help guide their next steps in further studying eribulin in this patient population.

“Although we did not meet our primary endpoints, this is still the first study demonstrating the activity of eribulin in earlier lines of treatment of metastatic breast cancer,” Kaufman said. “Eribulin is an active therapy in this setting, and overall, it has potentially comparable activity to capecitabine, which is a widely used treatment in this patient population.”

Source: SABCS