Comparison of overall survival after open vs. robot-assisted radical cystectomy: a target trial emulation approach to mitigate immortal time bias

Radical cystectomy is the standard treatment for muscle-invasive bladder cancer.With the growing adoption of robot-assisted radical cystectomy (RARC) since the early 2000s, comparative studies have shown inconsistent results, often because of methodological biases such as immortal time bias and selection bias.This study aimed to compare overall survival (OS) between open radical cystectomy (ORC) and RARC in patients with bladder cancer using a target trial emulation framework to minimize these biases.Using 45,595 patients identified from the Korean National Health Insurance Service database, we applied a cloning-censoring-weighting (CCW) procedure with inverse probability of censoring weights and compared the results with conventional approaches, including immortal-time-included, immortal-time-excluded, and landmark analyses.The conventional analyses yielded inflated hazard ratios suggesting a survival advantage for ORC, whereas the CCW-based analysis showed no significant difference in OS between the two approaches (hazard ratio 1.02, 95% CI 0.94-1.11).These results suggest that the previously reported survival advantage of ORC may largely reflect methodological bias rather than a genuine clinical benefit.