Comparing the real-world effectiveness of palbociclib plus letrozole versus letrozole alone in patients with advanced hormone-positive breast cancer

This study compared the real-world safety and effectiveness of the palbociclib (Ibrance) plus letrozole (Femara) versus letrozole alone in patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor-negative (HER2-) metastatic breast cancer (MBC). The data concluded that palbociclib in combination with letrozole significantly improved the outcomes of these patients in a real-world setting.

In MBC, the cancer is spread beyond the breast to distant sites. The outcomes of these patients are poor with standard therapies. Breast cancer (BC) cells can have on their surface certain proteins that help them grow. HR+/HER2- BC grows in response to female sex hormones such as estrogen and/or progesterone. Patients with this subtype of BC benefit from hormonal therapy such as letrozole. However, the risk of recurrence is high. 

Targeted therapies have improved the survival of patients with MBC. Palbociclib is a targeted therapy that blocks a protein that helps the cancer grow and spread. A previous clinical trial has shown that palbociclib in combination with letrozole improves the outcomes of patients with HR+/HER2- MBC. This led to the approval of this combination in these patients. 

However, patients are carefully selected in clinical trials. They are usually younger and have few other medical conditions than real-world patients. Therefore, the real-world safety and effectiveness of palbociclib plus letrozole in patients with HR+/HER2- MBC is still unknown.

This study involved 1430 women with HR+/HER2- MBC. 772 of them were treated with palbociclib plus letrozole (group 1) and 658 patients received letrozole alone (group 2). The average follow-up duration was 24.2 months for group 1 and 23.3 months for group 2.

The survival without cancer worsening was significantly longer in group 1 (20 months) compared to group 2 (11.9 months). Overall survival was also significantly longer in group 1. The addition of palbociclib to letrozole therapy was associated with a 34% higher chance of a longer survival.

After 2 years, 78.3% of the patients in group 1 were alive compared to 68% of those in group 2. 

The study concluded that palbociclib plus letrozole significantly improved the outcomes of patients with HR+/HER2- MBC compared to letrozole alone in a real-world setting.

The study was supported and funded by Pfizer, the manufacturer of palbociclib. This study included data from medical records. Some information might have been missing.