Cancer Risk and Mortality in Patients With Kidney Disease: A Population-Based Cohort Study

Rationale & Objective: Patients with chronic kidney disease (CKD) may be at increased risk for cancer. CKD may also be associated with worse cancer outcomes. This study examined cancer incidence and mortality across the spectrum of CKD. Study Design: Population-based cohort study. Setting & Participants: All adult Ontario residents with data on estimated glomerular filtration rate (eGFR) or who were receiving maintenance dialysis or had received a kidney transplant (2007-2016). Exposure: Patients were categorized as of the first date they had 2 eGFR assessments or were registered as receiving maintenance dialysis or having received a kidney transplant. eGFR levels were further categorized as >= 60, 45-59, 30-44, 15-29, and <15 mL/min/1.73 m(2); the latter 4 groups are consistent with KDIGO (Kidney Disease: Improving Global Outcomes) CKD categories G3a, G3b, G4, and G5, respectively. Outcomes: Overall and site-specific cancer incidence and mortality. Analytical Approach: Fine and Gray subdistribution hazard models. Results: Among 5,882,388 individuals with eGFR data, 29,809 receiving dialysis, and 4,951 having received a kidney transplant, there were 325,895 cancer diagnoses made during 29,993,847 person-years of follow-up. The cumulative incidence of cancer ranged between 10.8% and 15.3% in patients with kidney disease. Compared with patients with eGFR >= 60 mL/min/1.73 m(2), adjusted hazard ratios (AHRs) for a cancer diagnosis among patients with CKD G3a, G3b, G4, and G5 were 1.08 (95% CI, 1.07-1.10), 0.99 (95% CI, 0.97-1.01), 0.85 (95% CI, 0.81-0.88), and 0.81 (95% CI, 0.73-0.90), respectively. The AHRs for patients receiving dialysis and who had received a transplant were 1.01 (95% CI, 0.96-1.07) and 1.25 (95% CI, 1.12-1.39), respectively. Patients with kidney disease had higher proportions of stage 4 cancers at diagnosis. Patients with CKD G3a, G3b, and G4 and transplant recipients had increased risks of cancer-specific mortality (AHRs of 1.27 [95% CI, 1.23-1.32], 1.29 [95% CI, 1.24-1.35], 1.25 [95% CI, 1.18-1.33], and 1.48 [95% CI, 1.18-1.87], respectively). The risks of bladder and kidney cancers and multiple myeloma were particularly increased in CKD, and mortality from these malignancies increased with worsening kidney function. Limitations: Possible unmeasured confounding and limited ability to infer causal associations. Conclusions: Cancer incidence in the setting of kidney disease is substantial. Cancer risk was increased in mild to moderate CKD and among transplant recipients, but not in advanced kidney disease. Cancer-related mortality was significantly higher among patients with kidney disease, particularly urologic cancers and myeloma. Strategies to detect and manage these cancers in the CKD population are needed.