Breast Cancer Treatment Combo Falls Short of Overall Survival Goal

In the phase 3 PALOMA-3 trial, Pfizer’s palbociclib (Ibrance) narrowly missed reaching its secondary endpoint of overall survival (OS), according to a press release.

The PALOMA-3 trial evaluated palbociclib in combination with fulvestrant in women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer whose disease has progressed after prior endocrine therapy.

Palbociclib in combination with endocrine therapy is a standard of care for HR+, HER2- metastatic breast cancer. Palbociclib is approved for use in combination with fulvestrant based on results from the primary endpoint of progression-free survival (PFS). In the trial, palbociclib plus fulvestrant demonstrated a statistically significant and clinically meaningful improvement in PFS compared with placebo plus fulvestrant.

“While the difference in overall survival narrowly missed the threshold for statistical significance—a high bar for any trial in this patient population—it is similar, in absolute terms, to the improvement in median progression-free survival previously demonstrated in this trial,” Mace Rothenberg, MD, chief development officer of Oncology at Pfizer Global Product Development, said in the press release. “We are encouraged by these results, which build on the compelling clinical benefit delivered by Ibrance.”

The most common adverse effects associated with palbociclib included neutropenia, leukopenia, infections, fatigue, and nausea. Additionally, no new safety signals were identified as part of this final OS analysis.

“The duration of the survival in hormone receptor-positive metastatic breast cancer patients, and the potential for subsequent therapies to confound overall survival outcomes, make demonstrating statistically significant improvement in overall survival extremely difficult,” Nicholas Turner, MD, PhD, principal investigator of the PALOMA-3 trial, said in the press release.

Although the trial did not meet this secondary endpoint, Dr Turner noted that the results from the overall survival analysis support the strong PFS data and are encouraging for physicians and patients.

Reference

Pfizer announces overall survival results from phase 3 PALOMA-3 trial of Ibrance (palbociclib) in HR+, HER2- metastatic breast cancer [news release]. Pfizer’s website. https://www.pfizer.com/news/press-release/press-release-detail/pfizer_announces_overall_survival_results_from_phase_3_paloma_3_trial_of_ibrance_palbociclib_in_hr_her2_metastatic_breast_cancer. Accessed June 25, 2018.