Linear Mixed Models - Assessing the Relationship Between a Biomarker and Cancer Disease Status

Abstract: Previous research suggests that a specific biomarker measured in the blood correlates with cancer status, for a specific type of cancer: higher values of the biomarker are generally found in patients with progressive cancer. The aim of this study is to investigate this relationship using a Linear mixed model. Patients with a progressive disease have on average significantly higher values of the log of the biomarker and patients with partial or complete remission of the disease have on average significantly lower values of the logged biomarker, both compared to patients with a stable disease. Also, patients with a liver tumor have on average higher values of the log of the biomarker, compared to patients without. Including both a random intercept and a random slope in the Linear mixed model, in addition to the fixed effects, results in the best model fit. Due to the non-random sample used, these results are only valid for this specific sample but can be of guidance for the conduction and planning of future studies.