Cancer risk and mortality after solid organ transplantation: A population‐based 30‐year cohort study in Finland

Cancer is a significant cause of morbidity and mortality after solid organ transplantation (SOT) and related to lifelong immunosuppression. This retrospective registry study assessed for the first time in Finland population‐based cancer risk and cancer mortality after all SOTs (lung and childhood transplantations included) as standardized incidence ratios (SIRs) and standardized mortality ratios (SMRs). Data from transplant registries were linked with the data of Finnish Cancer Registry and Statistics Finland. We followed 6548 consecutive first SOT recipients from 1 January 1987 to 31 December 2016 translating to 66 741 person‐years (median follow‐up time 8.9 years [interquartile range 4.0‐15.1]). In total, 2096 cancers were found in 1483 patients (23% of all patients). Majority of cancers (53%) were nonmelanoma skin cancers (NMSCs). The overall SIR was 3.6 (95% confidence interval [CI]: 3.5‐3.8) and the SIR excluding NMSCs was 2.2 (95% CI: 2.0‐2.3). SIR for all cancers was highest for heart (5.0) and lowest for liver (2.7) recipients. Most common cancer types after NMSCs were non‐Hodgkin lymphoma (NHL), SIR 9.9 (95% CI: 8.5‐11.4) and kidney cancer, SIR 7.3 (95% CI: 6.0‐8.8). Cancer‐related deaths were 17% (n = 408) of all deaths after first month post transplantation. SMR for all cancers was 2.5 (95% CI: 2.2‐2.7) and for NHL 13.6 (95% CI: 10.7‐16.8). Notably, overall SIR for cancer was lower in later period (2000‐2016), 3.0 (95% CI: 2.8‐3.2), than in earlier period (1987‐1999), 4.3 (95% CI: 4.0‐4.5), P < .001. Decrease in cancer incidence was temporally associated with major changes in immunosuppression in the 2000s.