C-Reactive Protein in Solid Tumors: Clinically Meaningful Change

Background: C-Reactive Protein (CRP) is associated with cancer development, survival, and tumor recurrence. A barrier to its use is the inability to interpret changes in CRP levels. Aims: The aim of this study was to determine when a change in CRP is clinically meaningful. Methods: This was a retrospective cohort study of consecutive cancer patients. Those with a solid tumor diagnosis and at least two consecutive CRP measurements postdiagnosis were included. Subjects were divided into Baseline High CRP (bHCRP; CRP ≥ 10 mg/L) and Baseline Normal CRP groups (bNCRP; CRP < 10 mg/L), We identified appropriate CRP cut-off points for CRP levels changes; compared bHCRP and bNCRP; constructed Kaplan- Meier survival plots and Cox Proportional Hazard Model to confirm cut-off points in each group. Results: 1473 were eligible. In bHCRP group, Overall survival (OS) Mean (Standard Error) was 87(2) and 81(4) months for ≥ 50% vs < 50% CRP decrease respectively. In bNCRP group, OS was 90(3) and 105(3) months for ≥ 2x vs < 2x increase in CRP levels, respectively. These differences remained significant after adjusting for confounders. Conclusion: After a baseline normal CRP an increase of 2-fold or greater was associated with clinical and statistically significantly shorter OS. Conversely, after a baseline high CRP a 50% or greater decrease from baseline was associated with longer OS. Quantification of clinically meaningful CRP change could impact more effective CRP use as a biomarker, prognostic indicator and aid therapeutic decision making. This is especially important to reduce healthcare disparities in financially struggling healthcare systems.