GDF15 and neoplasm: Furthermore, when all patients with CRC were subdivided according to tumor stage, the gradual increase in serum MIC-1 levels was clearly discernible (P=0.0001), with significantly higher concentrations in stage IV than in stage I–III (P<0.0001), implying that the increased serum MIC-1 might have the positive correlation with occurrence and remote metastasis of CRC.