Objectives: To compare baseline characteristics and outcomes among SOTRs and IC patients with MCC, and to evaluate the efficacy and toxicity of anti-PD-L1 in SOTRs. Methods: We queried an MCC registry from our institution (April 1988–May 2024), extracting data on demographics, anti-PD-L1 response and immunosuppression regimens, along with incidence of allograft rejection and failure, for analysis. Results: We identified 1214 patients with MCC (37 SOTRs and 1177 IC patients); 8 of 37 SOTRs received anti-PD-L1. Median time from SOT to MCC diagnosis was 10 years (range 0.4–43). The proportion of patients with advanced MCC (≥ stage III) was 76% in SOTRs compared with 51% in IC patients (P = 0.004). SOTR status was associated with worse outcomes, including higher rates of disease progression [adjusted hazard ratio (aHR) 2.3], MCC-specific mortality (aHR 3.0) and overall mortality (aHR 3.9) (all P < 0.001 for the respective comparisons). Median time to death due to MCC for SOTRs was 2.7 years; 24% of SOTRs died within one year of diagnosis, in contrast with just 4% of IC patients. Median time to MCC progression for SOTRs was 8.6 months vs. 12 years for IC patients. Among SOTRs, 70% developed distant metastases within 2 years vs. 25% of IC patients. All eight MCC SOTRs treated with anti-PD-L1 were kidney transplant recipients, with five (63%) experiencing an objective response (two complete response, three partial response). However, two patients (29%) experienced irreversible graft failure within 9 weeks. Conclusion: SOTR status is a significant independent risk factor of a worse prognosis for MCC. This study represents the largest cohort evaluating the efficacy and safety of anti-PD-L1 in SOTRs with advanced MCC, highlighting the potential benefits in this population.

Advances in plasma cell dyscrasia therapies are improving survival and expanding kidney transplant eligibility. However, key challenges remain, including optimizing hematologic response pre–kidney transplant and managing immunosuppression to mitigate recurrence and avoid infection complications. Ongoing research and multidisciplinary collaboration are essential to refine transplant selection, integrate biomarkers for risk stratification, and develop tailored post–kidney transplant surveillance. These efforts may increase access to kidney transplant and improve outcomes for patients with plasma cell dyscrasias and end-stage kidney disease.

We used multivariable Cox regression models to compare incidence of invasive cancer, cutaneous squamous cell carcinoma (cSCC), posttransplant lymphoproliferative disorder (PTLD), death, and graft failure/retransplantation (GF/RT) between belatacept and tacrolimus users. Overall, cancer incidence was 10.1 and 12.6 per 1000 person-years in belatacept and tacrolimus users, respectively. We did not find increased risk with belatacept for cancer overall (adjusted hazard ratio [HR] 0.83, 95% confidence interval [95%CI] 0.53-1.30), individual cancer types, or cSCC. Belatacept was associated with increased risk of death (adjusted HR 1.22, 95%CI 1.04-1.43) but lower risk of GF/RT more than four years after transplantation (0.54, 0.35-0.83). PTLD risk was increased among EBV-seropositive KTRs (adjusted HR 1.96, 95%CI 1.03-3.73). This study provides reassurance that belatacept does not increase cancer risk among KTRs, and there was a long-term protective association for GF/RT. However, we found evidence suggesting a potential increased risk of PTLD and death with belatacept use.