Aim: This study assessed the combination of carcinoembryonic antigen (CEA) with the American Joint Committee on Cancer (AJCC) TNM staging system, aiming to improve the AJCC TNM staging system, in terms of prognostic accuracy and clinical management of rectal cancer.
Methods: Eligible patients (N=22,132) were selected from the Surveillance, Epidemiology, and End Results database between January 1, 2004, and December 31, 2010. Patients with elevated CEA levels were designated as "C1 stage" and those with normal CEA amounts as "C0 stage". The outcome of interest was cancer-specific survival (CSS). Cox proportional hazards regression analyses and Kaplan-Meier curves were used to identify independent prognostic factors and analyze the odds of CSS in patients with rectal cancer in different C and TNM stages, respectively.
Results: C1 stage was associated with a 61.0% risk increase in cancer-specific mortality (HR=1.610, 95% CI=1.219-1.705, P<0.001). In addition, C0-stage patients showed improved CSS compared with C1-stage counterparts. In addition, CSS was improved in stage IIB-C0 patients (HR=2.478, 95% CI=1.660-3.699) compared with stage IIIB-C1 patients (HR=2.431, 95% CI=2.021-2.924) or IIIA-C1 patients (HR=1.060, 95% CI=0.823-1.366, P=0.650) and stage IIC-C0 patients (HR=4.263, 95% CI=3.308-5.493) compared with stage IIIB-C1 or IIIA-C1 counterparts.
Conclusion: C stage is an independent prognostic factor of rectal cancer. The improved prognostic precision of the C-TNM staging system and, thus, more individualized risk-adaptive treatments support the incorporation of C stage into the AJCC TNM staging system in rectal cancer.
Keywords: AJCC; C-stage; SEER; rectal cancer.