(17) Association Between Tumor Location and Pathological Stage in Patients with Resectable Low Rectal Cancer: Evidence from 20-Years of Data in China

Publication Number: 1062

Background:
In patients with low rectal cancer, those with tumors adjacent to the sphincter complex have poor oncologic prognosis. Colorectal cancer prognosis is largely dependent upon pathological stage. However, the association between tumor location and stage is unknown.

Objectives:
To investigate the association between tumor location and pathological stage at the time of surgery in patients with nonmetastatic low rectal cancer based on 20 years of data in China.

Methods:
Between November 1999 and October 2021, a cohort of patients with pathologically confirmed primary malignant rectal tumor ≤5cm from the anal verge and who received selective surgery at Changhai Hospital in China, was identified. Demographic and clinicopathological data were extracted from electronic medical records. Survival data were collected from outpatient medical records and follow-up phone interviews. Pathological stage was measured from tumor specimens at the time of surgery and categorized into stage I to III based on the American Joint Cancer Committee 8th edition. Logistic regression adjusting for demographic and clinicopathologic confounders was used to assess the association between tumor location and pathological stage. A Cox proportional hazards regression model was used to assess overall survival associated with tumor location adjusting for the same confounders.

Results:
In our cohort, a total of 3,614 had a nonmetastatic tumor in the low rectum and received selective surgeries during the study period; 633 (17.6%), 881 (24.4%), 1,011 (28.0%), and 1,089 (30.0%) tumors were located at 0-≤2cm (ultra-low), 2-≤3cm, 3-≤4cm and 4-≤5cm from the anal verge, respectively. Of stage III tumors, 32.5% were located at 4-≤5cm from the anal verge compared to 26.3% of stage I. Multivariable analysis demonstrated that the odds of advanced pathological stage in tumors 0-≤2cm, 2-≤3cm, and 3-≤4cm, respectively, were less likely compared to tumors 4-≤5cm from the anal verge (0-≤2cm vs. 4-≤5cm: OR, 0.75; 95% CI, 0.61-0.92; 2-≤3cm vs. 4-≤5cm: OR, 0.72; 95% CI, 0.61-0.85; 3-≤4cm vs. 4-≤5cm: OR, 0.82; 95% CI, 0.70-0.95). The odds were slightly lower among patients with neoadjuvant therapy. A total of 2,655 patients had sufficient vital status data for inclusion in the survival analysis. The characteristics of those with and without a follow-up encounter were comparable. Among patients with a pathological stage II or III, ultra-low tumors had significant worse survival compared to tumors at 4-≤5cm (HR 1.45, 95% CI, 1.14-1.84).

Conclusions:
Lower tumor location was associated with an earlier pathological stage in low rectal cancer. Among patients with advance pathological stage, ultra-low rectal tumors had worse survival than higher tumors.