Mortality risk after cancer diagnosis in kidney transplant recipients: the limitations of analyzing hospital administration data alone.

Administrative data are frequently used for epidemiological studies but its usefulness to analyze cancer epidemiology after kidney transplantation is unclear. In this retrospective population-based cohort study, we identified every adult kidney-alone transplant performed in England (2003-2014) using administrative data from Hospital Episode Statistics. Results were compared to the hospitalized adult general population in England to calculate standardized incidence and mortality ratios. Data were analyzed for 19,883 kidney allograft recipients, with median follow-up 6.0 years' post-transplantation. Cancer incidence was more common after kidney transplantation compared to the general population in line with published literature (standardized incidence ratio 2.47, 95% CI: 2.34-2.61). In a Cox proportional hazards model, cancer development was associated with increasing age, recipients of deceased kidneys, frequent readmissions within 12 months post-transplant and first kidney recipients. All-cause mortality risk for kidney allograft recipients with new-onset cancer was significantly higher compared to those remaining cancer-free (42.0% vs. 10.3%, respectively). However, when comparing mortality risk for kidney allograft recipients to the general population after development of cancer, risk was lower for both cancer-related (standardized mortality ratio 0.75, 95% CI: 0.71-0.79) and noncancer-related mortality (standardized mortality ratio 0.90, 95% CI: 0.85-0.95), which contradicts reported literature. Although some plausible explanations are conceivable, our analysis likely reflects the limitations of administrative data for analyzing cancer data. Future studies require record linkage with dedicated cancer registries to acquire more robust and accurate data relating to cancer epidemiology after transplantation.