Effect of Gout and Diabetic Kidney Disease on Renal Cancer Development in Korea

Background Chronic kidney disease (CKD) and gout are risk factors for renal cancer. We analyzed the effects of comorbid diabetic kidney disease and gout on renal cancer. Methods This retrospective cohort study enrolled 847 884 patients with type 2 diabetes (T2DM) who underwent health assessments provided by the Korean National Health Insurance Service in 2009. Based on CKD occurrence (glomerular filtration rate <60 mL/min/1.73 m2) and gout (two outpatient visits or one hospitalization within 5 years), patients were classified into four groups: CKD−Gout− (87.5%), CKD−Gout+ (2.5%), CKD+Gout− (9.3%), and CKD+Gout+ (0.7%). Patients with incident renal cancer (ICD code C64) were followed up until December 2018. Results Renal cancer was diagnosed in 2376 patients (0.3%). Renal cancer incidence increased in sequential order of CKD−Gout− (0.29/1000 person-years [PY], CKD+Gout− ≈ CKD−Gout+ (0.44 and 0.48/1000 PY, respectively), and CKD+Gout+ (1.14/1000 PY). Comorbid gout differently increased renal cancer risk depending on CKD occurrence (hazard ratio [HR] = 1.28, 95% CI: 1.04–1.58 among those without CKD; HR = 1.95, 95% CI 1.45–2.63 among those with CKD; p-for interaction = 0.024). The interaction was significant, particularly in men and patients with a shorter diabetes duration (<5 y) and lesser medication use (no insulin or < 3 classes of oral hypoglycemic agents). Conclusions CKD and gout individually contributed to renal cancer incidence, and the risk is further increased when gout coexists with CKD. Screening for gout and appropriate management of CKD at an early T2DM stage may be beneficial.