Association Between Cancer and Incident Acute Kidney Injury Among Medicare Fee-for-Service Population.

Rationale & Objective: Acute kidney injury (AKI) is a frequent complication of cancer due to multiple factors. Our aim was to assess contemporary associations between various cancers and incident AKI among Medicare beneficiaries. Study Design: A retrospective observational study. Setting & Participants: Medicare fee-for-service beneficiaries aged ≥66 years. Exposure: New cancer diagnosis. Outcomes: Incidence of AKI. Analytical Approach: Follow-up started at cancer diagnosis or on December 31, 2014, for controls and ended at the date of AKI, death, cancer in the control group, or at 5 years, whichever occurred first. Overall and site-specific associations between cancer and AKI were assessed by cause-specific Cox models and Fine-Gray competing risk models, adjusting for age, sex, race and ethnicity, and comorbid conditions. Results: We identified 482,016 beneficiaries with newly diagnosed cancer and the same number of matched controls. The median follow-up time was 4.1 years (interquartile range [IQR], 1.0-5.0 years) and 4.8 (IQR, 1.7-5.0 years), respectively, for cancer cases and controls. The highest 5-year risk of AKI was observed in cancer of the renal pelvis and ureter 32.8% (95% confidence interval [CI], 30.7%-34.8%); multiple myeloma 32.6% (95% CI, 31.7%-33.4%); and kidney cancer 28.9% (95% CI, 28.2%-29.5%). The multivariable-adjusted subdistribution hazard ratio for AKI was significantly higher for multiple myeloma compared with controls and was significantly lower for cancers with high mortality, such as pancreatic, lung and bronchial, liver, gallbladder and biliary, or stomach cancer. Limitations: Potential misclassification from using International Classification of Diseases codes to identify cancer and AKI, residual confounding from unmeasured variables, lack of information on cancer stage and histology, and not accounting for cancer treatment including medication. Conclusions: Risks of AKI vary across cancer types. Multiple myeloma had the highest significant risk of AKI compared with controls.