C-reactive protein as a clinically useful biomarker of metastasis of renal cell carcinoma.

C-reactive protein (CRP) is an acute-phase reactant that can increase dramatically in response to a variety of pathologic states. Elevated pre- and postoperative CRP levels have been associated with an increased tumor burden and metastasis in kidney cancer. We report on a case that serves to highlight a potentially novel use for CRP monitoring in the postoperative management of renal cell carcinoma. Recently, we treated a patient who presented with a localized renal cell carcinoma and an elevated preoperative CRP level. Surgical pathology demonstrated negative surgical margins and absence of nodal metastasis. Postoperatively, the patient's serum CRP levels remained relatively low, consistent with his continued negative staging on CT scans. However, at 6 months postoperatively, the patient's CRP level increased 13-fold. His subsequent CT scan revealed "multiple pulmonary nodules consistent with progression of metastatic disease." This case demonstrates the potential for monitoring CRP in addition to, or instead of, standard restaging imaging.