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

## TL;DR

This study finds that survival outcomes for colorectal cancer vary by race and tumor location, especially in younger and older patients.

## Contribution

The study reveals distinct survival patterns by race and tumor subsite in early- and late-onset colorectal cancer.

## Key findings

- Non-Hispanic Blacks had worse survival for early-onset distal colon or rectal cancer compared to non-Hispanic Whites.
- Non-Hispanic Blacks showed better survival for late-onset rectal cancer compared to non-Hispanic Whites.
- Early-onset proximal colon cancer was associated with worse survival among non-Hispanic Whites.

## Abstract

The aim of this retrospective cohort study was to examine the effects of race and anatomic subsites on survival in early-onset (EOCRC) and late-onset colorectal cancer (LOCRC). In Louisiana, 10.7% of CRC cases were diagnosed at ages 20–49 years and were more likely to be non-Hispanic Blacks (NHB), female, rectal, and diagnosed at a distant stage compared with LOCRC. Overall racial disparities in survival were attenuated after full adjustment in both age groups. However, subsite-stratified analyses revealed heterogeneity. Among EOCRC patients with distal colon or rectal cancer, NHB had worse cancer-specific survival than non-Hispanic Whites (NHW). In contrast, among LOCRC patients with rectal cancer, NHB showed better survival than NHW. Survival patterns by anatomic subsite varied by race and age, with worse survival for early-onset proximal colon cancer among NHW and better survival for late-onset rectal cancer among NHB only.

Background: 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. Methods: 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. Results: 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. Conclusions: 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.