ABSTRACT
In many chronic diseases, the presence and concentration of molecular compounds circulating in the blood are associated with the stage of the disease and the risk of disease progression. In diabetes, for example, individuals with poor blood glucose control are at elevated risk of vascular complications involving the heart, eyes and kidneys. The level of glycosylated hemoglobin (HbA1c) in the blood reflects how well blood glucose levels are regulated, so measurements of HbA1c are used routinely in evaluating the effectiveness of medical or behavioral interventions in diabetes. In individuals with autoimmune diseases such as rheumatoid arthritis, levels of C-reactive protein (CRP) in the blood reflect the degree of inflammation which in turn predicts joint damage. In individuals with human immunodeficiency virus (HIV) infection, physicians monitor viral load, which is the concentration of the virus in the blood at any given time. In each of these settings, the measurements in the blood are termed markers which reflect disease activity or severity. They often play a useful role in predicting the course of disease and the occurrence of serious debilitating events. This chapter describes some ways to use marker data in patients with cancer metastatic to bone.
