Disease detected through screening is associated with superior survival outcomes in stage III colorectal cancer: a retrospective study in a Chinese high-volume cancer center

Colorectal cancer (CRC) screening reduces CRC mortality through early detection of cancer while decreasing incidence via removal of precancerous lesions (adenomas). Moreover, screening is associated with a reduction in mortality through detection of CRC in early stage. Yet it is unclear whether screening decrease mortality in locally advanced CRC. This study aims to investigate the pathological characteristics and survival outcomes of stage III CRC patients detected through screening. Notably in China and most developing countries where opportunistic screening predominates, understanding the stage-specific survival benefits could inform national screening policy optimization. This study involves a retrospective review of a cohort comprising 18,800 patients in Fudan University Shanghai Cancer Center, and a total of 4104 met the inclusion criteria. Propensity score matching (PSM) was conducted at a 1:4 ratio. Compared with cancers not detected through screening (n = 3967, 96.7%), cancers detected through screening (n = 137, 3.3%) were more likely to be older, to have colon cancer, vascular invasion, perineural invasion, smaller tumors or to receive radical surgery without neoadjuvant therapy. After PSM, cancer detection by screening was associated with better overall survival (OS) and a non-significant trend toward improved disease-free survival (DFS) in stage III CRC (5-year OS: 83.4% vs. 69.7%, P = 0.005; 3-year DFS: 75.6% vs. 70.3%, P = 0.064). Multivariate Cox analysis demonstrated that cancer detection by screening was an independently protective factor for OS (HR: 0.517, 95% CI: 0.341–0.782, P = 0.002) and DFS (HR: 0.683, 95% CI: 0.475–0.982, P = 0.040) in stage III patients. The study demonstrates that screening-detected cancers reduce mortality and recurrence risks among stage III CRC patients. These findings emphasize that screening improves survival outcomes not only through early-stage detection, and highlight the urgent need to increase screening coverage. The results support incorporating survival metrics into cost-effectiveness evaluations of screening programs, providing policymakers with more nuanced evidence.