Radiation-associated allograft injury in kidney transplant recipients with urothelial carcinoma

Background: This retrospective study was conducted to evaluate the safety of radiotherapy for kidney transplant recipients (KTRs) with urothelial carcinoma (UC). Methods: KTRs who developed UC and received radiotherapy with or without chemotherapy at our hospital from 1995 to 2016 were identified as the study group. All patients were treated by 3-dimensional conformal radiotherapy (3D-CRT) or intensity-modulated radiation therapy (IMRT). Various chemotherapy protocols were applied according to each patient's risk factors. The primary end point was graft failure. The tolerance dose of kidney was defined according to the QUANTEC report for evaluation. The cause of graft failure was determined by a kidney transplantation specialist. Results: The study group comprised ten patients with a median age of 63 years, and their diagnoses included 3 upper urinary tract UC, 4 bladder cancers, 3 synchronous UC in both the upper and lower urinary tracts. Half of the patients were treated by 3D-CRT, and the others were treated by IMRT. Dose distribution of only 2 treatment plans violated the tolerance dose of kidney (V6Gy <30%), but neither of them induced renal graft failure. There were four renal graft failures in the study group, which were due to different causes, including recurrent infection, second primary UC, and chronic allograft nephropathy. Conclusions: We suggest that the current irradiation technique is safe for kidney allograft when treating UC and can comply almost all the constraints suggested by the QUANTEC report. Following the QUANTEC report to constrain the radiation dose delivered to the kidney can be safe to avoid renal function impairment in KTRs.