The "Classification Pendulum" Of Stage I Colorectal Cancer: A National Level Analysis of the Survival Difference Between T1 And T2 Colorectal Cancer.

BACKGROUND The 8th edition of the American Joint Committee on Cancer classifies non-metastatic, node negative colorectal cancers invading the submucosa (T1) and muscularis propria (T2) as stage I tumors without further subclassification. OBJECTIVE The aim of the study was to compare survival of T1N0M0 versus T2N0M0 colorectal cancers and investigate factors associated with decreased survival. DESIGN Analysis of two large population-based datasets. SETTING The study was conducted analyzing data from the Surveillance Epidemiology and End Result (SEER) Program and the National Cancer Database. PATIENTS Adult patients undergoing major resection without further therapy for Stage I colorectal cancer. MAIN OUTCOME MEASURES Overall and disease-specific survival for T1 versus T2 cancers. Subgroup analyses by tumor location (colon versus rectum) were performed. RESULTS A total of 30,228 (36.4% T1 and 63.6% T2) and 41,670 (41.1% T1 and 58.9% T2) patients were identified in the SEER and National Cancer Database databases, respectively. The 5-year overall survival was 87.1% and 86.2% for patients with T1 versus 82.7% and 80.7% for patients with T2 (p<0.001) in the SEER and National Cancer Database respectively. The 10-year overall survival was 71.3% and 66.3% for patients with T1 versus 62.2% and 57.2% for patients with T2 tumors (p<0.001) in the SEER and National Cancer Database respectively. The 5- and 10-year disease-specific survival for colorectal cancer in the SEER was 97.0% (T1) versus 95.2% (T2), and 94.1% (T1) versus 90.3% (T2), respectively. African-American ethnicity (Hazard Ratio -HR 1.26 and 1.65 for overall survival and disease-specific survival-SEER; HR 1.20 for overall survival-National Cancer Database) was associated with worse survival. LIMITATIONS Intrinsic biases related to large administrative datasets. CONCLUSIONS Within stage I colorectal cancer, T2 tumors have decreased overall survival and disease-specific survival, as compared to T1 cancers. This survival difference may justify revising the American Joint Committee on Cancer staging system to include the subclassification of stage Ia (T1N0M0) and stage Ib (T2N0M0). See Video Abstract at http://links.lww.com/DCR/B659 .