Posttransplant Malignant Neoplasms in Solid Organ Transplant Recipients.

Importance: As long-term survival after solid organ transplant has improved, malignant neoplasms have emerged as a major determinant of outcomes. Objectives: To examine whether posttransplant cancer risk follows uniform trajectories over time or exhibits patterns across organ types and malignant neoplasm subtypes. Design, Setting, and Participants: This population-based cohort study used US nationwide data from 2000 to 2023 from the United Network for Organ Sharing registry. Participants were first-time recipients of heart, lung, liver, or kidney transplant. Analyses were conducted from March to June 2026. Main Outcomes and Measures: Incidence rates of first-occurring cancers for each cancer subtype were estimated per 100 person-years across 1-year intervals during the first decade after transplant. Temporal changes were evaluated using Poisson regression models adjusted for attained age, sex, transplanted organ type, and calendar period. Results: Among 622 330 transplant recipients (60 268 heart, 42 755 lung, 146 852 liver, and 372 455 kidney; median [IQR] age, 53 [41-61] years; 389 794 [62.6%] male), nonmelanoma skin cancers accounted for 30 049 of 54 709 cancers (54.9%). Lung, heart, and liver transplant recipients had consistently higher cancer incidence rates than kidney transplant recipients (eg, solid organ cancer: heart transplant: incidence rate ratio [IRR], 1.57 [95% CI, 1.51-1.63]; lung transplant: IRR, 2.01 [95% CI, 1.92-2.09]; liver transplant: IRR, 1.19 [95% CI, 1.14-1.22]). These differences increased with time since transplant for lung and heart transplant recipients (eg, solid organ cancer among heart vs kidney transplant recipients: year 1: IRR, 0.94 [95% CI, 0.83-1.07]; years 2-5: IRR, 1.54 [95% CI, 1.45-1.64]; years 6-10: IRR, 1.86 [95% CI, 1.75-1.98]). Three general temporal patterns were observed: an early peak followed by a decline for selected malignant neoplasms (including posttransplant lymphoproliferative disease and thyroid cancer), relatively stable rates for several cancer types, and progressively increasing incidence rates over time for selected solid organ malignant neoplasms (including lung, bladder, colorectal, and genital cancers). These patterns persisted after multivariable adjustment. Conclusions and Relevance: In this cohort study of solid organ transplant recipients, cancer incidence rates demonstrated distinct time-dependent patterns that varied by malignant neoplasm subtype and transplanted organ. These findings describe time-dependent risk trajectories among transplant survivors and may inform the timing of surveillance strategies and future studies of cancer risk in this population.