Pfizer Inc. announced detailed overall survival (OS) data from the PALOMA-3 trial, which evaluated IBRANCE (palbociclib) in combination with fulvestrant compared to placebo plus fulvestrant in women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer whose disease progressed on or after prior endocrine therapy. In the study, there was a numerical improvement in OS of nearly seven months with IBRANCE plus fulvestrant compared to placebo plus fulvestrant, although this difference did not reach the prespecified threshold for statistical significance (median OS: 34.9 months [95% CI: 28.8, 40.0] versus 28.0 months [95% CI: 23.6, 34.6]; HR=0.81 [95% CI: 0.64, 1.03], 1-sided p=0.0429). These data will be presented as a late-breaking oral abstract during the Presidential Symposium at the ESMO 2018 Congress (European Society for Medical Oncology) in Munich, Germany, and simultaneously published in The New England Journal of Medicine.
The difference in median OS demonstrated in this analysis (6.9 months) is consistent with the improvement previously demonstrated for the primary endpoint of median progression-free survival (mPFS). In the updated PFS analysis for this study (non-prespecified), the combination of IBRANCE plus fulvestrant showed a statistically significant and clinically meaningful 6.6-month mPFS improvement compared to placebo plus fulvestrant (11.2 vs. 4.6 months; HR=0.50 [95% CI: 0.40-0.62], p<0.000001). Overall survival is a secondary endpoint of PALOMA-3, and the trial design was not optimized to detect a statistically significant difference in OS.
“It’s noteworthy that the magnitude of progression-free survival benefit observed in PALOMA-3 has translated to a similar difference of nearly seven months in overall survival, which is clinically meaningful. This is particularly significant given the challenges of demonstrating overall survival in this disease setting, where post-progression therapy is often substantially longer than time on study,” said Massimo Cristofanilli, M.D., associate director for Translational Research at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University, as well as senior investigator of the PALOMA-3 trial. “The overall survival data, coupled with the previously demonstrated progression-free survival benefit, are encouraging for patients.”
At the time of this analysis, follow-up was 44.8 months and approximately 60 percent (n=310) of events had occurred in the 521 patients enrolled. Patients on both arms received up to 10 lines (range 1-10) of post-progression treatment.
The trend toward OS favoring the IBRANCE plus fulvestrant arm was observed across most subgroups, with hazard ratios consistent with the overall population. In addition, for the overall population, the difference in OS was associated with prolonged time from randomization to first use of chemotherapy post-progression, an exploratory endpoint (HR=0.58 [95% CI: 0.47, 0.73], 1-sided p<0.000001). Median time to chemotherapy was 17.6 months (95% CI: 15.2, 19.7) for patients who received IBRANCE plus fulvestrant, twice that observed in patients who received placebo plus fulvestrant (8.8 months [95% CI: 7.3, 12.7]).
“Delaying the need for chemotherapy is a central goal of treatment for women with this disease. These new data from PALOMA-3 show that adding IBRANCE to fulvestrant led to a substantial improvement in this important area,” said Nicholas Turner, M.D., Ph.D., professor of molecular oncology at The Institute of Cancer Research, London, and consultant medical oncologist at The Royal Marsden NHS Foundation Trust, as well as principal investigator of the PALOMA-3 trial. “The difference in overall survival and prolonged time to chemotherapy demonstrated in PALOMA-3 further support the role of IBRANCE in combination with endocrine therapy as a standard of care in HR+, HER2- metastatic breast cancer.”
“Looking at the data from the PALOMA-3 trial and across the PALOMA program, IBRANCE has transformed the treatment landscape for this disease,” said Mace Rothenberg, M.D., chief development officer, Oncology, Pfizer Global Product Development. “We are proud of the compelling body of evidence supporting the use of IBRANCE in this setting, and the difference this medicine continues to make in the lives of patients.”
The most common adverse reactions in PALOMA-3 included neutropenia, leukopenia, infections, fatigue and nausea. No new safety signals observed with longer follow-up were identified as part of this final OS analysis.