Background: Recent case series describe expression of BK virus (BKV) in tumor tissue obtained from renourinary cancers in kidney transplant recipients (KTRs). Thus, BKV may contribute to a heightened risk of these cancers in KTRs. We hypothesized that KTRs with post-transplant BKV nephritis (BKVN) would have an increased risk of developing renourinary cancers.

Methods: Data on all KTRs from 2003-2013 were obtained from the Transplant Cancer Match Study, which links the US transplant registry to 17 state cancer registries covering 48% of US transplants. Patients with (BKVN+) and without BKVN (BKVN-) were identified at 6-24 months post-transplant. During subsequent follow-up, standardized incidence ratios (SIRs) were used to quantify risk of kidney, renal pelvis, ureter, bladder and prostate cancers relative to the general population. Poisson regression was used to calculate incidence rate ratios (IRRs) comparing cancer risk adjusted for sex, age, calendar year, and use of anti-thymocyte globulin induction therapy (ATG).

Results: 55,697 transplant recipients were included, of whom 2015 (3.6%) were BKVN+. Compared with BKVN- patients, BKVN+ patients were more likely to be male (70% vs 60%; p<0.0001), transplanted in a later era (24% vs 11%; p<0.0001; 2010-2013), and to have received ATG (52% vs 41%; p<0.0001). Risks were similarly elevated (~5-fold) for kidney cancer in both BKVN+ and BKVN- KTRs (SIRs 4.6 vs 4.7; N=235) and risk was not increased in either group for prostate cancer (SIRs 0.6 vs 0.9, N=260). Renal pelvis and ureter cancers were too rare to analyze separately (N=7 and N=2, respectively). In contrast, for bladder cancer, risk was more elevated in BKVN+ than BKVN- KTRs (SIRs 3.5 vs 1.5; N=54), corresponding to an adjusted IRR of 2.9 (95%CI 1.0-8.2). Similar results were obtained for all urothelial cancers (renal pelvis, ureter, and bladder cancers: adjusted IRR of 3.3, 95%CI 1.3-8.2). The 4 bladder cancers in BKVN+ KTRs were invasive transitional cell carcinomas.

Conclusions: This large epidemiologic study suggests that patients with BKVN are at heightened risk of urothelial malignancies, especially bladder cancer, although these cancers were rare. Together with reports describing BKV detection in tumor tissues, these results support an etiologic role for BKV in these cancers.

CITATION INFORMATION: Gupta G, Kuppachi S, Kalil R, Buck C, Lynch C, Engels E. BK Virus Infection and Risk of Urinary Tract Cancers Among Kidney Transplant Patients in the Transplant Cancer Match Study. Am J Transplant. 2017;17 (suppl 3).

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