First-line, reduced-dose eribulin mesylate disappoints in older adults with metastatic breast cancer

Among older patients with metastatic breast cancer (mBC), first-line treatment with reduced-dose eribulin mesylate is reasonably safe but yields a low disease control rate (DCR), reports a recent phase II trial.

Researchers enrolled 77 mBC patients with a median age of 76 years, who were treated with eribulin mesylate at a reduced dose. The primary study outcome was a DCR ≥55 percent, while secondary endpoints included objective response (OR), progression-free (PFS) and overall (OS) survival, and treatment-related neurotoxicities.

First-line eribulin mesylate was only able to achieve a DCR of 40 percent (95 percent confidence interval 31–50 percent), indicating that the compound failed its primary endpoint. OR was also low at 22 percent, while median PFS and OS were 5.4 and 16.1 months, respectively.

Thirty-five percent of patients needed dose adjustments, while nine patients received more than 15 cycles.

In terms of safety, 62 percent (n=48) of patients developed at least one grade 3 toxicity. Nevertheless, neurotoxicity did not appear to accrue over the course of the treatment, with median patient-reported neurotoxicity scores remaining constant throughout at least 15 cycles. The most common reason for treatment discontinuation was disease progression, reported by 57 percent of participants.

“Prolonged treatment and disease control were possible in a considerable proportion of the population without cumulative neurotoxicity,” the researchers said. “However, this reduced dose is apparently in the range of the minimal effective dose, as shown by the complete lack of efficacy in the patients who required further dose reductions.”

“Thus, our results do not support the approach of a reduced starting dose for older patients,” they added.