Background and Aims: Intrahepatic cholangiocarcinoma (iCCA) and hepatocellular carcinoma (HCC) are the most common primary liver cancers (PLCs). Differences in their clinical features and outcomes are open for investigation in a large-scale study. We aim to investigate the differences in clinical features and outcomes between iCCA and HCC. Approach and Results: The Surveillance, Epidemiology, and End Results Program 18 Database (2000-2017) was used to extract demographic and clinical features of HCC and iCCA patients. Logistic regression analysis was performed to identify factors associated with iCCA diagnosis versus HCC. Cox regression analysis was used to assess factors affecting overall survival (OS). There were 13,611 iCCA and 96,151 HCC patients. Half of iCCA (50.7%) and three quarters of HCC (76.3%) patients were male. Diagnosis in recent year, age (<50 or ≥65), female sex, non-Hispanic White race, higher income, rural area, and higher tumor burden were independently associated with iCCA diagnosis versus HCC. Patients with iCCA had worse OS than those with HCC (9 vs. 13 months; P < 0.001). However, OS was comparable between iCCA and HCC in multivariable analysis (adjusted hazard ratio [aHR] = 1.02; 95% CI = 0.99-1.05). In subgroup analyses, iCCA was associated with better OS than HCC in patients with tumor ≥5 cm (aHR = 0.83; 95% CI = 0.80-0.86), lymph node involvement (aHR = 0.76; 95% CI = 0.72-0.81), distant metastasis (aHR = 0.76; 95% CI = 0.73-0.79), poorly/undifferentiated tumors (aHR = 0.88; 95% CI = 0.83-0.94), and those receiving noncurative treatment (aHR = 0.96; 95% CI = 0.93-0.98). Conclusions: We identified the demographic, socioeconomic, and clinical features associated with iCCA diagnosis over HCC among patients with PLC. Although iCCA patients presented at an advanced stage, OS was similar between iCCA and HCC in multivariable analysis. iCCA was associated with longer OS for subgroups with poor prognostic features.
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