Abstract 307P
Background
CDK4/6 inhibitors(i) have shown progression-free survival (PFS) and overall survival (OS) benefits in clinical trials but best use in sequence of therapy is not well established in clinical practice. Current clinical questions include how to sequence with other therapies in HR +, HER2 - metastatic breast cancer (MBC). Using real world evidence (RWE), we reviewed the outcome of CDK4/6i combinations in HR +, HER2 - MBC according to different lines of treatment.
Methods
Using IQVIA's diversified oncology US EHRs (2015 Q4 to 2020 Q1) ≥18 years with HR +, HER2 - MBC were classified into the following cohorts (Cs) based on different sequential use of drugs: C1: Hormonal therapy as First line therapy (FLT) followed by CDK 4/6i combinations, Everolimus combinations (EC) and Chemotherapy (CT) C2: CDK 4/6i combinations as FLT followed by EC and CT; C3: EC as FLT followed by CDK 4/6i combinations and CT; C4: CT as FTL and subsequent therapy. Patient outcomes for each C – Progression (time to next treatment), PFS (Time to next treatment or death) and OS were analyzed.
Results
16,017 MBC patients who started FLT between 2015 Q4 to 2020 Q1 were studied. Test of proportions generated statistically significant results between C1&C2 showing that more patients tend to survive longer when they receive CDK4/6i combinations as FLT (C2 80% vs. C1 87%). C3 did not show any statistical significance due to small number of patients. On comparison between Cs applying Chi-Square test for independence, it turned out that more patients died in C4 (p-value < 0.000, C4 vs. C1/C2/C3) and rest of groups were similar except C1 vs. C2 where the results were close to statistical significance at 95% CI (p-value = 0.070). The median PFS observed for CDK4/6i combinations across Cs was 13.5 months (m) C1; vs. 14.1 m C2; vs. 13.2 m C3 respectively and PFS at > 24 m 14.4% C1; vs. 14.7% C2; vs. 12.2% C3.
Conclusions
Retrospective analysis showed that OS was better in C2 compared to other Cs, however PFS during CDK4/6i combinations was very similar. Further investigation into cohort demographics along with propensity score matching based on other variables and detailed CDK4/6i combination analysis can help us to explain the current findings.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Silvia Comis.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.