Risk of bladder cancer in renal transplant recipients: a meta-analysis

Renal transplantation is the treatment offered for patients with end-stage renal failure. The outcomes of renal transplantation have improved considerably over the past decades, especially with the introduction of highly active immunosuppressive drugs that dramatically decrease the incidence of acute graft rejection and improve graft and patient survival rates (O'Grady et al, 2002; Knight et al, 2009). However, treatment of renal transplant recipients (RTRs) with immunosuppressive agents was considered to lead to malignancy by supporting oncogenesis caused by certain viruses or by impairing immune surveillance resulting in faster tumour growth (Rama and Grinyo, 2010). As a matter of fact, malignancy is the third leading cause of death among RTRs after transplation, following cardiovascular disease and infection (Briggs, 2001). Compared with the general population, an overall two- to seven-fold elevated risk of malignancies was documented among RTRs (Kyllonen et al, 2000; Adami et al, 2003; Vajdic et al, 2006; Villeneuve et al, 2007; Krynitz et al, 2013). The most frequent malignancies are skin cancers and lymphomas, followed by Kaposi's sarcoma, lip, cervical, perineal, renal, hepatocellular carcinomas, and other sarcomas (Penn, 2000; Kauffman et al, 2006). Increased incidence of other malignancies, such as thyroid and lung in transplant recipients, has also been reported (Grulich et al, 2007; Karamchandani et al, 2010). Several studies have showed increased risk of bladder cancer after renal transplantation (Hoshida et al, 1997; Cheung et al, 2012; Li et al, 2012). However, not all studies have shown a similar association (Serraino et al, 2005; Vegso et al, 2007). In this study, we performed a meta-analysis to determine whether the overall SIR of bladder cancer is increased in RTRs compared with the general population, which might be helpful in determining whether conclusive recommendations for bladder cancer screening in RTRs are needed.