Polyomavirus replication & smoking are independent risk factors for bladder cancer after renal transplantation

Background. Solid organ transplant recipients are at increased risk for developing malignancies. Polyomaviruses (PV) have been historically associated with experimental tumor development and recently described in association with renourinary malignancies in transplant patients. The aim of this study was to investigate the relationship between PV replication and smoking, and the development of malignant neoplasms in kidney transplant recipients. Methods. A retrospective case-control study was conducted for PV replication in all kidney biopsies and urine cytologies performed between 1998 and 2014 fromkidney transplant recipients at the University of Maryland Medical Center. Polyomavirus-positive patients (n = 943) were defined as having any of the following: a kidney biopsy with PV associated nephropathy, any urine cytology demonstrating "decoy" cells, and/or significant polyomavirus BK viremia. Polyomavirus-negativematched patients (n = 943) were defined as lacking any evidence of PV replication. The incidence ofmalignancy (excluding nonmelanoma skin tumors) was determined in these 1886 patients and correlated with demographic data and history of smoking. Results. There was a 7.9% incidence of malignant tumors after a mean posttransplant follow-up of 7.9 ± 5.4 years. Among all cancer subtypes, only bladder carcinoma was significantly associated with PV replication. Bymultivariate analysis, only PV replication and smoking independently increased the risk of bladder cancer, relative risk, 11.7 (P = 0.0013) and 5.6 (P = 0.0053), respectively. Conclusions. The findings in the current study indicate that kidney transplant recipients with PV replication and smoking are at particular risk to develop bladder carcinomas and support the need for long-term cancer surveillance in these patients.