Researchers measured the effect of ribociclib dose modifications and found benefit was maintained in patients with HR+/HER2- advanced breast cancer who required modifications from the recommended starting dose of 600 mg daily for 3 weeks on and 1 week off, according to a poster presented at the 2022 ASCO Annual Meeting.

Included, eligible postmenopausal patients were enrolled in the randomized 1:1 first-line ribociclib plus letrozole or placebo MONALEESA-2 trial. To explore the association of overall survival, relative dose intensity 2, 2 time-dependent variables, and dose reduction (with/without modifications from 600mg starting dose) were included as covariates.

The final study cohort included 334 patients, of which 209 (62.6%) had ≥1 ribociclib dose reduction and 125 (37.4%) had 0 ribociclib dose reductions. Results showed median overall survival was 66.0 (95% CI, 57.6-75.7) months in patients with ≥1 ribociclib dose reduction vs 60.6 (95% CI, 42.5-79.2) months in patients with no ribociclib dose reductions (HR, 0.87 [95% CI, 0.65-1.18]). 

Median overall survival was observed to be 62.6 (95% CI, 50.0-80.7) months, 63.9 (95% CI, 48.8-not reached [NR]) months, and 65.3 (95% CI, 50.5-NR) months, respectively (HR low vs high, 0.99 [95% CI, 0.69-1.42]; HR medium vs high, 0.97 [95% CI, 0.62-1.38] in patients with low (< 64.27%), medium (64.27%-95.86%), and high (> 95.86%) relative dose intensity 2.

Researchers did not observe a relationship between ribociclib dose reduction, relative dose intensity 2, and overall survival, but overall survival benefit with ribociclib was observed across all groups.

Reference:
Hart LL, Bardia A, Beck JT, et al. Impact of ribociclib (RIB) dose modifications (mod) on overall survival (OS) in patients (pts) with HR+/HER2- advanced breast cancer (ABC) in MONALEESA(ML)-2. J Clin Oncol. 2022;40(suppl 16): abstract 1017. doi:10.1200/jco.2022.40.16_suppl.1017