Effect of Race and Tumor Subsite on Survival Outcome in Early- and Late-Onset Colorectal Cancer

<b>Background</b>: While colorectal cancer (CRC) incidence and mortality have declined among patients aged ≥50 years (late-onset), rates are increasing in those aged <50 years (early-onset). Historically, non-Hispanic Whites (NHW) have had better 5-year survival compared with non-Hispanic Blacks (NHB), and rectal cancer has had better outcomes than colon cancer. Whether these disparities by race and tumor location are evident for both early-onset (EOCRC) and late-onset (LOCRC) CRC remains unclear. <b>Methods</b>: CRC cases diagnosed from 2011 to 2022 were identified from the Louisiana Tumor Registry. EOCRC was defined as diagnoses at ages 20-49 years, and LOCRC was defined as diagnoses at ages ≥50 years. Racial groups included NHW and NHB; tumor location was categorized as proximal colon, distal colon, or rectum. Cox regression was used to assess unadjusted and adjusted overall and cancer-specific survival. <b>Results</b>: Of 23,738 CRC patients, 10.7% were diagnosed at age <50 years. Compared to LOCRC, EOCRC patients included a higher proportion of NHB (37.5% vs. 32.6%) and rectal tumors (44.4% vs. 29.9%). NHB had worse overall survival than NHW in early-onset distal colon cancer (adjusted HR [aHR] = 1.358; 95%CI: 1.024-1.801). Conversely, NHB had better overall (aHR = 0.899; 95%CI: 0.831-0.973) and cancer-specific survival (aHR = 0.873; 95%CI: 0.793-0.960) in late-onset rectal cancer. Among EOCRC NHW, proximal tumors were associated with worse overall (aHR = 1.407; 95%CI: 1.102-1.796) and cancer-specific survival (aHR = 1.379; 95%CI: 1.057-1.799) compared with distal tumors. <b>Conclusions:</b> Survival differences by race and tumor subsite are observed between EOCRC and LOCRC, with NHB showing a lower hazard of death in some LOCRC subgroups. These findings highlight the need to consider the age of onset and tumor location when addressing racial disparities in CRC outcomes.