EP690 - A National Study on Treatment Patterns and Survival Outcomes in T3N0 Colon vs Rectal Cancer

Purpose/Background: The management for T3N0 colorectal cancer continues to be a topic of great interest, with practices differing between primary colon and rectal cancer, respectively. This study evaluates national treatment trends while identifying clinical and socioeconomic (SES) predictors of therapy selection and survival outcomes.

Methods/Interventions: A retrospective analysis of the National Cancer Database (NCDB, 2018-2020) was done for adults (≥18 years old) with T3N0M0 adenocarcinoma of either the colon or rectum. Treatment was categorized into four groups: surgery only, surgery and chemotherapy, surgery and radiation (± chemotherapy), or definitive chemoradiation (no surgery). Demographic, clinical, and SES data were collected. Categorical variables were compared using the X^2 test. Survival analyses were done using Kaplan-Meier and log-rank test. Multivariate logistic regression was conducted to identify predictors of treatment type and multivariate Cox proportional hazards regression was conducted to identify predictors of overall survival (OS), adjusting for age, sex, comorbidity (Charlson-Deyo Index), and SES.

Results/Outcomes: Out of a total of 1,769,819 colorectal cancer patients (1,329,615 colon and 440,207 rectal cancers, respectively), there were 35,522 adult patients with T3N0M0 adenocarcinoma (34,364 colon and 1,158 rectal cancers, respectively). Medial age was 71 [61-80] years old and 50% were male. Treatment category by site varied with colon having 78% surgery only and 20% surgery and chemotherapy vs. rectal cancer with 92% surgery and radiation (±chemotherapy) and 1.5% definitive chemoradiation and was statistically different (p < 0.0001). When looking at OS, rectal cancer had overall greater survival compared to colon cancer (p=0.0086), colon primary had improved survival with adjuvant chemotherapy vs. surgery alone (p < 0.0001), and rectal cancer had improved survival with surgery and radiation (±chemotherapy) vs. definitive chemoradiation (p=0.02). After logistic regression, younger age (OR 0.97, p< 0.0001), lower comorbidity (OR 0.95, p=0.0002), and private insurance (OR 0.84, p=0.01) were predictors of therapy type. After Cox regression, older age (HR 1.06, p< 0.0001), male sex (HR 1.32, p< 0.0001), and higher comorbidity (HR 1.27, p< 0.0001) predicted worse OS, while private insurance (HR 0.74, p=0.008), higher income (HR 0.91, p< 0.0001), and higher education (HR 0.96, p=0.04) were protective. The highest benefit of OS came from adjuvant chemotherapy (HR 1.07, p=0.04).

Conclusion/Discussion: Management of T3N0 colorectal cancers vary significantly with colon cancer being primarily managed surgically and rectal cancer treated mainly with a combination of surgery and radiation (±chemotherapy), demonstrating improved OS. However, disparities amongst SES and insurance status continue to act as determinants of treatment and outcomes, further highlighting the need for equitable resources and management for this intermediate-risk population.

Table 1
Baseline Characteristics of T3N0 Colon vs. Rectal Cancer Patients
Figure 1
T3N0 Colon vs. Rectal Cancer Kaplan-Meier Survival Analysis by Treatment