Diagnostic contribution of C-reactive protein kinetics for gastric metastasis from renal cell carcinoma

C-reactive protein (CRP) has been reported as a useful biomarker for renal cell carcinoma (RCC). Here, we report a case in which CRP kinetics of a continuous increase in CRP levels led to the detection of RCC metastasis to the stomach, a rare metastatic site. A 58-year-old man diagnosed with metastatic RCC underwent cytoreductive nephrectomy. Four months after the surgery, his CRP level started to increase continuously. Thus, we suspected disease progression. Extensive studies, including thoracoabdominal computed tomography and bone scan, however, detected neither local recurrences nor metastatic lesions. A further increase in CRP levels and gradual progression of anemia prompted us to investigate the digestive tract. Gastric endoscopy finally revealed gastric metastasis. After partial gastrectomy, his CRP level immediately decreased to a normal level. The patient is currently alive with no evidence of disease progression and his CRP level remains within the normal range, 44 months after his metastatic RCC diagnosis. The continuous increase in CRP levels reflected the development of gastric metastasis. The decrease in CRP levels after partial gastrectomy was indicative of a good response to treatment. This case demonstrates that CRP kinetics may be helpful in predicting disease progression as well as response to therapeutic intervention.