End Point Surrogacy in First-Line Chronic Lymphocytic Leukemia

Area of Science:

• Oncology
• Clinical Trials
• Hematology

Background:

• Surrogate endpoints like progression-free survival (PFS) and minimal residual disease (MRD) are crucial for estimating treatment efficacy in chronic lymphocytic leukemia (CLL) studies.
• Understanding the correlation between these surrogate endpoints and overall survival (OS) is vital for advancing CLL therapies.

Purpose of the Study:

• To analyze the patient-level and trial-level correlation between PFS and MRD with OS in first-line CLL trials.
• To validate these correlations in the context of targeted therapies (TT) versus chemotherapy/chemoimmunotherapy (C/CIT).

Main Methods:

• Patient-level correlation was assessed using data from 4,237 patients in German CLL Study Group (GCLLSG) trials.
• A joint-frailty copula model was employed to validate correlations, particularly for TT.
• A meta-analysis of 16 first-line phase III CLL trials (2008-2024) involving 8,065 patients was conducted to quantify treatment-effect correlation.

Main Results:

• Patient-level correlation between PFS and OS was strong (Spearman Rho >0.9).
• Treatment-effect correlation between PFS and OS was moderate (R=0.75) for C/CIT and strong for TT (tau=0.91).
• End-of-treatment MRD showed a strong correlation with PFS (R=0.88) but a weaker correlation with OS (R=0.71).

Conclusions:

• Patient-level correlation between PFS and OS is confirmed for TT in CLL.
• Treatment-effect correlation between PFS and OS requires further investigation.
• MRD response strongly correlates with PFS but not consistently with OS, highlighting the need for more randomized trials with MRD data.