33 Impact of Immortal Time Bias in Mortality of Colorectal Cancer patients using Taiwan Cancer Registry

Oregon Convention Center 

Introduction
Colorectal cancer (CRC) had higher cancer-related mortality. Due to the time bias between the cancer diagnosis and initial treatment date, the decreasing mortality after a patient receiving treatment may be exaggerated. This study aimed to explore the impact of immortal time bias on the mortality risk of CRC patients for improving the accuracy of risk prediction post-cancer diagnosis using the real-world databases, Taiwan Cancer Registry.
Methods
This study establishes a mortality risk model for CRC patients from 2012 to 2023. For assessing the immortal time bias of the mortality risk, Cox regression with landmark analysis and time-varying analysis approaches were used to estimate the hazard ratios with 95% confidence intervals.
Results and Conclusion
The time interval between diagnosis and treatment could be estimated using landmark and time-varying analysis approaches for accuracy of mortality prediction. The results indicated the correct design of methodology could elevate the precision of cancer mortality. In conclusion, exploring correlations over the time since diagnosis provides a more comprehensive perspective for improving CRC diagnosis and treatment.

Immortal Time Bias

Colorectal Cancer

Taiwan Cancer Registry

Cancer Mortality 

Section on Statistics in Epidemiology