Real-World Evidence Shows Pfizer’s Ibrance Improves Breast Cancer

Pfizer recently presented real-world evidence demonstrating a significant benefit for patients treated with Ibrance (palbociclib) combined with an aromatase inhibitor (AI) compared to AI alone.  

The cohort study enrolled 2,888 hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–), and metastatic breast cancer (mBC) patients. In the study, Ibrance combined with AI improved overall survival (OS) in post-menopausal women and in men with HR+ HER2– mBC treated in routine clinical practice in the United States.  

Additionally, the median overall survival was substantially longer in the Ibrance group versus the AI group (49.1 months versus 43.2 months). And real-world median progression-free survival was 19.3 months versus 13.9 months, respectively.  

These findings represent a 24% reduction in the risk of death and a 30% reduction in the risk of progression. Researchers did not collect safety data as part of this analysis. 

“I’ve witnessed first-hand the positive impact of palbociclib in combination with endocrine therapy in patients with HR+, HER2– metastatic breast cancer.” Hope S. Rugo, MD, lead researcher and professor of medicine at the University of California San Francisco (UCSF) Helen Diller Family Comprehensive Cancer Center, said in the announcement.  

“It is encouraging to see associated improved overall survival extend beyond my own practice in the real-world setting, and these additional results, along with clinical trial data, may help healthcare providers make more fully informed treatment decisions for their patients,” Rugo continued.  

FDA first approved Ibrance in 2015 to treat advanced metastatic breast cancer. Since then, providers have prescribed the drug to more than 450,000 patients across over 100 countries. 

In March 2021, Pfizer announced that first-line therapy with Ibrance combined with letrozole improved real-world progression-free survival and overall survival in women with HR+, HER2–-, and mBC, compared with letrozole alone. 

At a follow-up of nearly two years, median real-world progression-free survival was 20 months with Ibrance plus letrozole versus 11.9 months with letrozole alone. These findings represented a 42% reduction in the risk of progression and a 34% reduction in the risk of death.  

Notably, this trial represented the first comprehensive comparative effectiveness analysis of survival outcomes for a CDK4/6 inhibitor in routine clinical practice.