Abstract 4019: Effect of time interval from diagnosis to treatment on mortality in colorectal cancer by stage in Korea

Background: Colorectal cancer (CRC) is one of the most common cancers worldwide and a major contributor to the disease burden. Treatment delay, defined as the time interval from diagnosis to treatment initiation, is an emerging public health concern. While treatment delays in cancer may not directly cause fatal health outcomes, some studies have reported associations though the evidence remains inconclusive. Therefore, we aimed to investigate the impact of treatment delays on all-cause mortality in CRC patients in Korea, stratified by cancer stage. Methods: A retrospective cohort study was conducted using the sample cohort of CRC patients from the Cancer Public Library Database, which integrates data from four public sources in Korea. The study included patients diagnosed with CRC (ICD-O-3: C18-C20) between 2012 and 2019, with mortality follow-up until 2021 and health service utilization data until 2022. Treatment delay was categorized using two thresholds: 3 months and 6 months. Cumulative all-cause mortality was analyzed with the Kaplan-Meier methods, and group differences were assessed with log-rank tests. Adjusted hazard ratios (aHR) and 95% confidence intervals (CI) were estimated by Cox proportional hazard models, adjusted for sex (male/female) and age at diagnosis (<50, 50-59, 60-69, 70-79, ≥80). All analyses were stratified by SEER cancer summary stage (localized, regional, distant). Results: Of 53,485 CRC patients, 28,520 were analyzed. Most had regional stage CRC (54.7%). The proportion of patients having treatment delays of ≥3 months was highest in the localized stage (5.5%), then in the distant (3.6%) and regional (1.7%) stages, with a similar trend observed for delays of ≥6 months (localized: 2.4%; distant: 1.7%; regional: 0.8%). Longer treatment delays were significantly associated with higher 5-year cumulative mortality across all stages (<3 months vs ≥3 months vs ≥6 months; localized: 12.7% vs 21.4% vs 37.6%; regional: 22.9% vs 35.4% vs 52.2%; distant: 77.4% vs 84.0% vs 84.1%; p<0.001 for all). Treatment delays of ≥3 months, compared to <3 months, significantly increased the risk of death, with the highest risk in the regional stage (aHR: 1.69 [95% CI: 1.42-2.02]), followed by localized (1.55 [1.24-1.93]) and distant (1.29 [1.09-1.53]) stages. For delays of ≥6 months (vs <6 months), the highest risk was examined in localized stage (2.91 [2.24-3.78]), followed by regional (2.63 [2.07-3.35]) and distant (1.47 [1.15-1.89]) stages. Conclusion: Treatment delays of more than 3 months were significantly associated with higher all-cause mortality across all stages of CRC in Korea, with a more pronounced impact in the localized and regional stages. These findings emphasize the importance of timely treatment, especially for early-stage colorectal cancer. Citation Format: Ji Yoon Baek, Curi Park, Ji Won Park, Aesun Shin. Effect of time interval from diagnosis to treatment on mortality in colorectal cancer by stage in Korea [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4019.