Increased Cancer Risk in Patients with Kidney Disease and Venous Thromboembolism: A Population-Based Cohort Study

BACKGROUND: Venous thromboembolism (VTE) may be a harbinger of cancer in the general population. Patients with kidney disease have an a priori increased VTE risk. However, it remains unknown how a VTE affects subsequent cancer risk in these patients. OBJECTIVES: To examine the cancer risk in patients with kidney disease following a VTE. METHODS: We conducted a nationwide population-based cohort study in Denmark (1996-2017), including all VTE patients with a diagnosis of kidney disease. We calculated absolute risks of cancer (accounting for competing risk of death) and age-, sex-, and calendar-period standardized incidence ratios (SIRs) comparing the observed cancer incidence with national cancer incidence rates and cancer incidence rates of VTE patients without kidney disease. RESULTS: We followed 3,362 VTE patients with kidney disease (45.9% females) for a median follow-up time of 2.4 years (interquartile range: 0.6-5.4). During follow-up, 464 patients were diagnosed with cancer, of whom 169 (36.4%) were diagnosed within the first year. The 1-year absolute risk of any cancer was 5.0% (95% confidence interval [CI]: 4.3-5.8), with a SIR of 2.9 (95% CI: 2.5-3.4) when compared with the general population, and 2.0 (95% CI: 1.8-2.4) when compared with VTE patients without kidney disease. During subsequent years of follow-up, the SIRs declined to 1.5 (95% CI: 1.3-1.6) when compared with the general population, and 1.1 (95% CI: 0.9-1.2) compared with VTE patients without kidney disease. CONCLUSION: Patients with hospital-diagnosed kidney disease have increased cancer risk after VTE, especially within the first year following the VTE diagnosis.