Abstract 254P
Background
Palbociclib dose reductions do not affect efficacy in the clinical trial setting, as previous data have shown. No significant differences in progression-free survival were observed across the various palbociclib doses in the real world, but more dose reductions have been reported. Our aim was to evaluate if dose reductions in Palbociclib affect the duration of treatment (DoT) and overall survival (OS) of metastatic breast cancer (mBC) patients in the first and second-line setting in the real world.
Methods
We identified HR+/HER2- mBC female patients (pts) treated with first and second-line Palbociclib between January 2016 and June 2020 using the institutional computerized prescriber order entry system and performed a retrospective review of the electronic medical records. Our primary outcome was to compare DoT and OS among the groups treated with three different doses of Palbociclib, (125 mg, 100 mg and 75 mg) with the Kaplan Meier method. Secondary outcomes were to evaluate the impact of age and Body Mass Index (BMI) among the dose groups on DoT and OS.
Results
100 pts were included, with 65 and 35 pts receiving palbociclib as first and second line, respectively. 28% of the pts tolerated Palbociclib at a dose of 125 mg, 29% were dose-reduced to 100 mg, and 43% to 75 mg. The number of pts requiring dose reductions here was higher than that reported in PALOMA-2 (72% vs 36%). After a median follow-up of 28.9 mos, 33% remained on Palbociclib, 59% progressed or died, and 6% discontinued due to toxicity. Median DoT was 21.2 mos for all pts, 10.9 mos for pts receiving 150mg, 23 mos for pts receiving 100 mg and 26.7 mos for pts receiving 75 mg. Differences between groups were not statistically significant. Mean OS was 48.9 mos for all pts; 37.4 mos for pts receiving 150mg dose, 45.3 mos for pts receiving 100 mg and 54.9 mos for pts receiving 75 mg (p .02) which was statistically significant. There was no statistically significant difference in DoT or OS among the groups when considering age and BMI factors.
Conclusions
In this retrospective cohort of mBC patients treated with Palbociclib in either first or second-line, more dose reductions were observed than that reported in PALOMA-2, but there was no negative impact on median DoT or mean OS when compared with the group receiving the standard dose of 125mg.
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
R. Pezo: Financial Interests, Personal, Advisory Role, Honoraria/advisory: Pfizer; Financial Interests, Personal, Advisory Role, Honoraria/advisory: EMD Serono; Financial Interests, Personal, Advisory Role, Honoraria/advisory: Merck; Financial Interests, Personal, Advisory Role, Honoraria/advisory: Novartis; Financial Interests, Personal, Advisory Role, Honoraria/advisory: BMS; Financial Interests, Personal and Institutional, Research Grant: Merck; Financial Interests, Personal and Institutional, Research Grant: Novartis; Financial Interests, Personal and Institutional, Research Grant: BMS. All other authors have declared no conflicts of interest.