Renal cell carcinoma and risk of second primary cancer: A Danish nationwide cohort study

Aim To examine the risk of second primary cancer in patients with incident renal cell carcinoma (RCC). Methods We identified all patients diagnosed with incident RCC during 1995–2019, using population‐based Danish medical registries. Patients were followed from the date of RCC diagnosis until any second primary cancer diagnosis, death, emigration, or December 31, 2019, whichever came first. We computed the absolute risk, standardized incidence ratio (SIR), and excess absolute risk of second primary cancer, with 95% confidence intervals (CIs), among patients with RCC compared to the general population. Results The absolute 1‐ and 20‐year risks of any second primary cancer were 2.8% and 17.8%, respectively. Within 1 year after RCC diagnosis, we detected 20 excess cancer cases per 1000 person‐years (PY) (SIR, 2.3; 95% CI: 2.1–2.6). Moreover, we detected an additional four excess cancer cases per 1000 PY during 1 to