Incidence and Prognostic Significance of Second Primary Cancers in Renal Cell Carcinoma

Background: The survival of patients with renal cell carcinoma (RCC) has improved in recent years. However, data on the risk of developing a second cancer after a diagnosis of RCC is limited. We used the data available in the Surveillance Epidemiology and End Results (SEER) database to estimate the risk of second metachronous primary cancers in patients diagnosed with RCC between 1973 and 2006. Furthermore, we also investigated the effect of the second primary cancers (SPCs) on the survival of RCC patients. Results: A total of 3795 cases of SPCs were registered in the SEER between 1973 and 2006. The ratio of observed/expected number of SPCs in RCC was 1.18, which was significantly greater than expected. Solid tumors comprised 90% of all second malignancies in RCC patients, with the most second cancers reported in the prostate gland and the digestive and respiratory systems. The overall risk of second primaries was highest in patients aged over 30 years at the time of diagnosis. The site-specific risk of second cancers varied with the age at diagnosis, sex, race of the patient, size of the primary renal tumor, and history of radiation therapy. Patients with second primaries had a significantly longer overall survival than those without second malignancies. An interval of < 1 year between the diagnosis of RCC and the second primary was the strongest predictor of poor overall survival in RCC patients with a second malignancy. Conclusions: Patients with RCC are at a significantly higher risk of developing a second malignancy, suggesting the need for careful surveillance for their early detection and management.