*Purpose: Long term data after Banff borderline changes suspicious for acute T cell-mediated rejection (BDR lesion) are scarce, and hence, there is little evidence to guide optimal treatment after the occurrence of BDR lesion. This study aimed to assess the long term impact of early subclinical BDR lesions on long term renal graft function.

*Methods: We retrospectively evaluated the long term results of 614 patients who showed no acute rejection (NAR) or BDR lesion on early protocol biopsies (<3 week post-transplant) after renal transplantation between July 2008 and Dec 2015. Long term graft function, including estimated glomerular filtration rate (eGFR) change, subsequent rejection, development of de novo DSA, and graft survival, were compared among the three patient groups (NAR group; BDR-Tx group, BDR lesion with treatment; BDR-NTx, BDR lesion without treatment) according to the biopsy results and treatment provided.

*Results: The study included 429 patients with NAR (NAR group) and 285 patients with BDR during the early protocol biopsy. Among the 385 patients with subclinical BDR lesions, patients treated (BDR-Tx, n=76) had lower eGFR at biopsy (median 74.2 mL/min/1.73 m² vs. 79.8 mL/min/1.73 m², p=0.017), higher t-score (>t1, 12.8% vs 2.6%, p=0.014), and more IFTA (13.8% vs. 2.6%, p=0.020) than untreated patients (BDR-NTx, n=109). When eGFR change over 60 months of the three groups were compared using logistic generalized estimate equation, although eGFR differed between the three groups (χ2=9.3, df=2, p=0.009), and showed a significant difference over time (χ2=92.9, df=5, p<0.001), there was no between-group difference in the change of eGFR over time (χ2=12.3, df=10, p=0.26). BDR-NTx and BDR-Tx had a higher risk of developing future T cell-mediated rejection, according to COX univariate analysis (p=0.003). Other factors associated with risk of subsequent T cell-mediated rejection in COX univariate analysis were donor age, recipient age, recipient sex, eGFR at biopsy, HLA mismatch number, peak pretransplant PRA, and ptc at protocol biopsy. COX multivariate analysis including the relevant showed significantly increase in the risk of acute T cell-mediated rejection in BDR-NTx group (HR 1.63, 95%CI 1.13-2.35, p=0.01), but not in BDR-Tx group (HR 1.28, 95% CI 0.93-1.48, p=0.131) compared to NAR group.). There was no significant difference in the occurrence of future antibody-mediated rejection or graft failure between the three groups.

*Conclusions: While early subclinical BDR lesion may be associated with persistence or development of further T-cell mediated pathology when not treated, neither BDR lesion or its treatment were related to long term graft function decline or failure.

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