Second Primary Cancer Risk among Kidney Cancer Patients in Korea: A Population-Based Cohort Study

PURPOSE Secondary primary cancers (SPCs) commonly arise in patients with renal cell carcinoma (RCC). We designed the present study to estimate the SPC incidence in Korean patients with RCC. MATERIALS AND METHODS The study cohort was population-based and consisted of 40,347 individuals from the Korean Central Cancer Registry who were diagnosed with primary renal cancer between 1993 and 2013. Standardized incidence ratios (SIRs) for SPCs were estimated for different ages at diagnosis, latencies, diagnostic periods, and treatments. RESULTS For patients with primary RCC, the risk of developing a SPC was higher than the risk of developing cancer in the general population (SIR, 1.13; 95% confidence interval, 1.08 to 1.18). Most cancer types showed higher incidences in patients with RCC than in the general population. However, the relative incidence of gastric cancer as an SPC varied by age. Gastric cancer incidence was elevated in young patients (< 30 years) with RCC, but reduced in older (≥ 30) patients with RCC. Patients with advanced RCC died prematurely, regardless of SPC development. In contrast, those with early-stage RCC survived for longer periods, although SPC development affected their post-RCC survival. After SPC development, women had better survival than men. CONCLUSION In Korean patients with primary RCC, the incidence of SPC was 13% higher than the incidence of cancer in the general population. These findings may play important roles in the conduct of follow-up evaluations and education for patients with RCC.