Correlation Between Tumor Size and Serum Biomarker Levels

I believe that at some time in the very near future, we will be able to diagnose a wide variety of tumors with great specificity on the basis of their serum proteomic signatures in the serum. I must admit, however, that I have paid insufficient attention to the quantitative assessment of serum biomarkers as opposed to their qualitative value. A recent paper (see: Cancer Screening: A Mathematical Model Relating Secreted Blood Biomarker Levels to Tumor Sizes) therefore caught my attention and provided some some early hints about how the titer of a  circulating biomarker can be used to provide additional clinical information:

This study introduced a linear one-compartment mathematical model that allows estimation of minimal detectable tumor sizes based on blood tumor biomarker assays. Assuming physiological data on CA125 and PSA from the literature, the model predicted detection limits of tumors that were in qualitative agreement with the actual clinical performance of both biomarkers. The model may be helpful in future estimation of minimal detectable tumor sizes for novel proteomic biomarker assays if sufficient physiologic data for the biomarker are available. The model may address the potential and limitations of tumor biomarkers, help prioritize biomarkers, and guide investments into early cancer detection research efforts.

Two conditions were assumed in the study:

(1) the compartment (plasma) is well-mixed and kinetically homogenous; (2) the tumor biomarker consists of a protein that is secreted by tumor cells into the extracellular fluid compartment, and a certain percentage of the secreted protein enters the intravascular space at a continuous rate.

 I find the idea of estimating the minimal detectable size of a tumor based on biomarker titers to be intriguing. My vision of integrated diagnostics in the future is that multiplexed biomarker panels will be used for cancer screening of the general population or to assess symptomatic patients. Positive results from these panels can then be used to select the most appropriate medical imaging studies to confirm the diagnosis. This imaging process will surely be made easier if some idea of the minimal anticipated size of the putative tumor in addition to the organ site can be communicated to the radiologists interpreting the studies.