Background: Stage IV colorectal cancer encompasses various clinical conditions. The aim of this study was to validate the utility of the recent AJCC stage IV colorectal cancer sub-classification, and to establish a prognostic scoring system using independent factors.
Methods: We conducted a retrospective analysis using data from the multicenter registry. Factors affecting the curative resection and prognosis were analyzed in patients with stage IV colorectal cancer.
Results: Of the 60,176 patients who received surgery for colorectal cancer, 9,624 (16.0 %) were classified as stage IV. The prognoses of patients with peritoneum-only metastasis were superior to those of patients with a stage IVB (P < 0.0001). Of the 11 independent prognostic factors identified, eight with a hazard ratio greater than 1.3 (depth of tumor invasion, regional lymph node metastasis, histologic grade, liver metastasis, lung metastasis, distant lymph node metastasis, peritoneal metastasis, and curative resection) were used in the prognostic scoring system. The scoring system gave one or two points for the presence of each prognosis risk factor, resulting in a total score ranging from 0 to 9. The 5-year overall survival rates of patients with a total score of 0-2, 3, 4, 5, and 6-9 were 50.4, 30.4, 17.7, 7.7, and 4.0 %, respectively (P < 0.0001).
Conclusion: Although the AJCC staging for patients with stage IV colorectal cancer reflected the prognosis, patients with peritoneum-only metastases should be classified as stage IVA. The prognostic scoring system using eight independent factors is useful in predicting the survival of patients with stage IV colorectal cancer.