Cancer Risk After Simultaneous Pancreas-Kidney Transplantation Compared With Kidney Transplant Alone: A Propensity-Matched Cohort Study.

BACKGROUND

Post-transplant malignancy is a major determinant of long-term outcomes after solid organ transplantation. Whether simultaneous pancreas-kidney (SPK) transplantation confers a differential post-transplant cancer risk compared With kidney transplantation alone (KA) remains uncertain.

METHODS

We conducted a retrospective propensity score-matched cohort study of adult transplant recipients at three Mayo Clinic sites between 2001 and 2017. SPK recipients (n = 484) were matched 1:1 with KA recipients using propensity scores. The primary outcome was post-transplant cancer incidence analyzed using Fine-Gray competing risks regression with death as a competing event. Standardized incidence ratios (SIRs) were calculated relative to the US general population. Cox proportional hazards models with cancer modeled as a time-varying covariate evaluated associations with mortality and death-censored graft failure.

RESULTS

Over a median follow-up of 10 years, overall cancer incidence was similar between SPK and KA recipients (subdistribution hazard ratio [sHR] 0.80, 95% CI 0.63-1.02; p = 0.07). The observed trend toward lower cancer incidence in SPK recipients was driven by a lower incidence of non-melanoma skin cancer (NMSC) (sHR 0.72, 95% CI 0.53-0.97; p = 0.03), which was attenuated after age adjustment (sHR 0.76, p = 0.07). Incidence of other malignancies did not differ between groups. Compared with the US general population, cancer risk excluding NMSC was approximately twofold higher in both cohorts (SIR 2.18 for SPK vs. 2.23 for KA). Incident malignancy was strongly associated with increased mortality (HR 3.40 in KA and 2.07 in SPK) but not with a statistically significant increase in graft failure.

CONCLUSIONS

In this propensity score-matched cohort study, overall post-transplant malignancy incidence was comparable between SPK and KA recipients. Both groups experienced substantially elevated cancer risk relative to the general population, and incident malignancy was strongly associated with mortality. These findings suggest that malignancy risk is driven primarily by shared immunologic and demographic factors rather than transplant type.