S0191 Comparing Pathologic Features of Different Colonic Segments in Non-Hereditary Young Onset Colorectal Cancer

Abstract

INTRODUCTION: Young patients with non-hereditary colorectal cancer (CRC) have unfavorable pathologic characteristics. The features and survival outcomes in different colonic segments are to be determined. METHODS: In this retrospective observational study we randomly selected patients (aged 18–50) with a histopathologic diagnosis of CRC at Carilion Clinic, Roanoke, from 2002 to 2017. Patients with inflammatory bowel disease and predisposing genetic syndromes were excluded. Demographics, polyp and tumor features, and mortality were obtained from the electronic medical record. Two pathologists reviewed histopathology to minimize diagnostic variability. The cumulative risk of mortality among patients with different pathologic features was estimated using Kaplan Meier curves. RESULTS: We identified 139 patients (Mean age, 41.6 ± 6.9 years; 53.2% males) with non-hereditary CRC. Thirty percent of tumors were located in the right colon (RC), 35.4% in the left colon (LC), and 34.5% in the rectum (Rec). In patients with resected tumors, a cancer-adjacent polyp was identified in 78.8% (RC), 73.7% (LC), and 47.4% (Rec). Lymphovascular invasion (LVI) was present in 59.0% compared to 38% (LC) and 25% (Rec). Perineural invasion (PNI) was present in 25.0% compared to 10.8% (LC) and 14.35% (Rec). RC tumor budding was (14%) compared to 13.1% (LC) and 2.9% (Rec), and tumor deposits in 30% compared 18.9% (LC) and 17.7% (Rec). Intratumoral lymphocytes were present in 32.1% (RC) compared to 15.8% (LC) and 3.03% (Rec). Intratumoral neutrophils were present in 3.6% in the RC compared to 10.5% (LC) and 3.03% (Rec). Thirty-two percent (RC) had Crohn’s like response compared to 26.3% (LC) and 3.0% (Rec). Microsatellite instability (MSI) accounted for 9.4% of (RC) tumors and 8.1% of (LC) tumors but was not present in rectal tumors. Among patients who had repeat colonoscopy for surveillance, about 90.0% of patients with RC cancer did not receive surveillance colonoscopy within 1 year of cancer diagnosis compared to 42% (LC) and 55.6% (Rec). Patients with Rec cancer had decreased survival compared to patients diagnosed with RC and LC cancers (P = 0.04) (Figure 1). CONCLUSION: Right colon tumors accounted for higher rates of unfavorable pathologic features compared to left colon and rectal tumors. Adherence to USMSTF surveillance recommendations is poor, especially in RC tumors. Patients with rectal cancer had the poorest survival outcomes compared to right and left colon tumors.Figure 1.: Interval time of diagnosis until last visit based on segment.