Initial real-world experience with ribociclib in advanced breast cancer

Abstract

Purpose

CDK4/6 inhibitors, such as ribociclib, are recommended in combination with hormonal therapy to treat advanced/metastatic hormone receptor-positive, HER2-negative breast cancer. The objectives of this study are to evaluate the therapeutic outcome and tolerance of ribociclib in patients treated at our institution.

Methods

The initial cohort of patients who received >1 cycle of ribociclib between December 2018 and March 2022 were included. Rates of adverse events (AEs) related dose reduction and discontinuation of ribociclib were used as a surrogate marker for intolerance.

Results

Sixty-eight female patients were included. Ribociclib was administered with letrozole or fulvestrant in the first-, second-, third-, and fourth-line palliative hormonal therapy settings in 29 (42.6%), 26 (38.2%), 12 (17.6%) and 1 (1.5%) patients respectively. Adverse events (AEs) related dose reduction was reported in 30 (44%) patients. Ribociclib was permanently discontinued in 42/68 (61.8%) patients [Disease progression 33/68 (48.5%) and AEs 9 (13.2%)]. Objective response was documented in 10/61 (16.4%) evaluable patients. The median progression free survival (PFS) was 18 months (95% CI: 11.7–24.3). The median overall survival (OS) was not reached and 84% of patients were alive at 3 years.

Conclusions

Although objective response rates were modest in this mixed cohort of heavily pretreated patients, ribociclib combined with letrozole or fulvestrant has shown robust PFS and OS in real-world practice. AEs related treatment discontinuation rate is higher than that reported in clinical trials with stringent inclusion criteria.