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 analysed 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 mellitus (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 (International Classification of Diseases 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⁻ and CKD⁻Gout⁺ (0.44 and 0.48/1000 PY, respectively) and CKD⁺Gout⁺ (1.14/1000 PY). Comorbid gout increased renal cancer risk depending on CKD occurrence {hazard ratio [HR] 1.28 [95% confidence interval (CI) 1.04–1.58 among those without CKD; HR 1.95 [95% CI 1.45–2.63] among those with CKD; P-value for interaction = 0.024}. The interaction was significant, particularly in men and patients with a shorter diabetes duration (<5 years) and lesser medication use (no insulin or fewer than three classes of oral hypoglycaemic 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.