Abstract 234P
Background
Proton pump inhibitors (PPIs) have been associated with drug interactions resulting in decreased bioavailability of many anticancer drugs. Cyclin-dependent kinases 4 and 6 inhibitors (CDK4/6i) are approved in combination with aromatase inhibitors for patients with hormone receptor (HR)-positive metastatic breast cancer (mBC). The data comparing the CDK4/6i interactions with PPIs and its impact on clinical outcomes is sparse. We present the following study comparing CDK4/6i and their interaction with PPIs to determine the efficacy of their concurrent use.
Methods
We conducted a retrospective observational study. Patients in age group 18-90 years, with HR-positive, HER2-negative mBC treated with either of the 2 CDK4/6i (palbociclib and abemaciclib) from January 2017 to August 2022 were included. Clinical and demographic data was obtained by chart review. The primary outcome was to compare the median progression-free survival (mPFS) for patients on CDK4/6i with PPI versus without PPI. The secondary outcome was to compare the mPFS for the 2 CDK4/6i, stratified based on PPI use.
Results
281 patients were included (277 females and 4 males), mean age of 67.51 years. 191 patients received PPI with CDK 4/6i. There was no difference in mPFS between the groups receiving CDK4/6i with and without PPI, 18 vs 17 months, respectively. Cox proportional hazard regression model showed that overall risk of progression was 17% lower in the group receiving PPI (Table). Patients on palbociclib and abemaciclib had higher mPFS with concomitant administration of PPI (p-value 0.2405 and 0.6561, respectively). Table: 234P
mPFS (in months) in the CDK4/6i groups
| mPFS with PPI | mPFS without PPI | Cox proportional hazard regression model analysis for risk of progression | |
| All CDK4/6i | 18 | 17 | HR 0.83 [0.60, 1.14], p = 0.2518 |
| Palbociclib | 19 | 19 | HR 0.81[0.56, 1.16], p = 0.2490 |
| Abemaciclib | 11 | 10 | HR 0.84 [0.38, 1.86], p = 0.6665 |
Conclusions
Our study results did not reveal a significant difference in mPFS between patients who received CDK4/6i with or without PPI. However, our study had a small sample size and short duration of follow-up. Further studies are warranted to establish the relationship of CDK4/6i and PPI interaction with clinical outcomes.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
C. Hilton: Other, Advisory Role: John Hopkins Hospital, Curio Science, Gilead Sciences, Biotheranostics, AstraZeneca; Other, Speaker’s Bureau: AstraZeneca/Daiichi Sankyo; Other: Gilead Sciences, Clinical Education Alliance, Targeted Oncology, OncLive/MJH Life Sciences. All other authors have declared no conflicts of interest.