Abstract 5015: Pretreatment carcinoembryonic antigen levels predict survival in patients with rectal adenocarcinoma
Authors: Makarova-Rusher Oxana V. , Strauss Julius , Ulahannan Susanna , Kim Chul , Del Rivero Jaydira , Duffy Austin , Greten Tim F. 
Published: July 2016

Abstract
Background: Population-based studies have reported elevated Carcinoembryonic Antigen (CEA) level as an independent prognostic factor in patients with colon cancer, thus supporting inclusion of CEA-based C stage in classical TNM staging for colon cancer. However, the effect of C-stage incorporation on outcomes for patients with rectal adenocarcinoma is unknown.
Methods: The Surveillance, Epidemiology and End Result (SEER) database was used to collect data from 2004 to 2007 for patients with rectal adenocarcinoma by topography code C20.9 and histology codes 8140-8144, 8210-8211, 8220-8221, 8260-8263, 8440, 8480-8481, and 8490. CEA stage C0 = normal CEA or C1 = elevated CEA was assigned to patients with known pretreatment CEA levels. Observed survival (OS) by American Joint Committee on Cancer (AJCC) stages I-IV and CEA stage C0 or 1 was determined using Kaplan Meier method. Relative survival (RS) as a net measure of cancer survival adjusted for sex, race, age and date was calculated in addition to observed survival (OS). Log-rank was used to compare observed survival. Z-test with corresponding p values was used to compare 5-year relative survival.
Results: We identified 25,241 patients with a record of histologically confirmed invasive rectal adenocarcinoma. Approximately half (N = 13,151) of these patients had records of pretreatment CEA levels: N = 6,360 stage C1, N = 6,690 stage C0 and a small number (101) with borderline CEA levels. Mean age at diagnosis was similar in both groups, 64.2 for C0 and 64.7 for C1. Among patients with C1 disease the leading AJCC stage was distant metastatic, stage IV (33.8%) followed by 25.8% stage III, 20.7% stage II, 13.8% stage I, and 5.9% unknown stage. In contrast to CI disease, the most common stage for C0 was stage I (35.2%), and only 6.3% of patients with C0 were diagnosed with stage IV disease. Observed survival by each of I-IV AJCC TNM stages was decreased for C1 stage relative to C0, p&lt;0.001. The 5-year OS by AJCC TNM stage for C1 was as follows: 56.7% for IC1 (CI = 53.3-59.9), 55.4% for IIC1 (CI = 52.7-58.1), and 53.4% for IIIC1 (CI = 51.0-55.8). The 5-year OS by AJCC TNM stage for C0 was 75.8% for IC0 (CI = 74.1-77.5), 68.8% for IIC0 (CI = 66.5-71.0), 65.4% for IIIC0 (63.3-67.5). Stage shifting was observed with IIIC0 disease, which had superior OS as compared to stage IIC1 and IC1 (p&lt;0.001). For stage IV disease, the 5-year OS for C0 was more than double the 5 year OS for C1, 20.8 (17.1-24.9) vs. 7.9 (6.8-9.1), p&lt;0.001. In concordance with this OS data, the 5-year relative survival analysis also showed a significant difference between C1 and C0 stages of rectal adenocarcinoma in the respective AJCC TNM stages, p&lt;0.001.
Conclusion: Our study suggests that pretreatment CEA levels predict survival in patients with rectal adenocarcinoma, in accordance with previous data in colon cancer. Therefore, our study supports C-stage inclusion in AJCC TNM staging for this neoplasm. Further prospective confirmatory studies are warranted.
Citation Format: Oxana V. Makarova-Rusher, Julius Strauss, Susanna Ulahannan, Chul Kim, Jaydira Del Rivero, Austin Duffy, Tim F. Greten. Pretreatment carcinoembryonic antigen levels predict survival in patients with rectal adenocarcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5015.