Aim: To analyze the survival trends in colorectal cancer (CRC) based on the different classifications recommended by the seventh and eighth editions of the American Joint Committee on Cancer staging system (AJCC-7th and AJCC-8th).
Methods: The database from our institution was queried to identify patients with pathologically confirmed stage 0-IV CRC diagnosed between 2006 and 2012. Data from 2080 cases were collected and 1090 cases were evaluated through standardized inclusion and exclusion criteria. CRC was staged by AJCC-7th and then restaged by AJCC-8th. Five-year disease-free survival (DFS) and overall survival (OS) were compared. SPSS 21.0 software was used for all data. DFS and OS were compared and analyzed by Kaplan-Meier and Log-rank test.
Results: Linear regression and automatic linear regression showed lymph node positive functional equations by tumor-node-metastasis staging from AJCC-7th and tumor-node-metastasis staging from AJCC-8th. Neurological invasion, venous infiltration, lymphatic infiltration, and tumor deposition put forward stricter requirements for pathological examination in AJCC-8th compared to AJCC-7th. After re-analyzing our cohort with AJCC-8th, the percentage of stage IVB cases decreased from 2.8% to 0.8%. As a result 2% of the cases were classified under the new IVC staging. DFS and OS was significantly shorter (P = 0.012) in stage IVC patients compared to stage IVB patients.
Conclusion: The addition of stage IVC in AJCC-8th has shown that peritoneal metastasis has a worse prognosis than distant organ metastasis in our institution's CRC cohort. Additional datasets should be analyzed to confirm these findings.
Keywords: Colorectal cancer; Disease-free survival; Peritoneal metastasis; Prognosis; Tumor-node-metastasis staging.