Post-kidney transplant malignancies affect graft survival: results from a time-dependent analysis

Aim of this study was to evaluate the association between cancer occurrence and risk of graft failure in kidney transplant recipients. From 1998 to 2013, 672 adults receiving their first kidney transplant from a deceased donor, with at least six months of follow-up, were included in the study. To illustrate the effect of tumors incidence on graft failure risk, a modified Kaplan-Meier method was used. To quantify the tumor effect as hazard ratio, multivariable adjusted Cox models were fitted considering the diagnosis of non-cutaneous malignancies (NCM) and non-melanoma skin cancer (NMSC) as a time-dependent covariates. The 5-year cumulative incidence of graft failure was 7.5% (95%CI: 5.3-10.0), with 59 events (39 due to chronic rejection and 20 for other causes). Forty patients developed a NCM (5-yrs cumulative incidence: 5.6%), and 47 developed a NMSC (5-yrs cumulative incidence: 6.5%). From the multivariable Cox model, the adjusted hazard ratio of graft failure associated with NCM was 3.27 (95%CI=1.44-7.44, p=0.005). The occurrence of a NMSC was not associated with graft failure (HR = 0.80; 95% CI = 0.30-2.14, p = 0.66). The model validation procedure (a leave-one out cross validation) showed a C-statistics of 0.80 (95%CI: 0.72-0.88) for the cross-validated cohort, ruling out model overfitting and validating its predictive ability. Investigating the effects of NCM on cause-specific graft failure, an NCM diagnosis seemed to have a different association (P = 0.002) when considering graft failed due to chronic rejection (HR 0.55, 95% CI: 0.07-4.08) or for other causes (HR 15.59, 95% CI 5.43-44.76). The reduction of the immunosuppression after NCM was not associated with a greater risk of graft failure. In conclusion, our data suggest that post-transplant NCM may be a strong risk factor for graft failure, particularly for causes other than chronic rejection, and more efforts should be addressed to improve graft outcomes acting on malignancy-associated nephropathies.