Radiation exposure to the kidney with interstitial iridium-192 high-dose-rate brachytherapy: Extent and rare morphologic changes of radiation nephropathy.

Purpose: We sought to investigate functional parameters and morphologic changes of the renal parenchyma after treatment with image-guided brachytherapy using single-fraction irradiation (high-dose-rate brachytherapy - HDR-BT) of primary kidney lesions, and primary and secondary lesions of the liver, lymph node, and adrenal gland close to renal structures.

Material and methods: Patients ineligible for surgery were included. We prospectively investigated renal function loss within one year via renal scintigraphy and laboratory parameters (KDOQI stage). Radiation exposure to the kidney was measured by volume receiving 5 Gy (V₅). We observed morphologic changes on CT or MRI, with follow-up every three months.

Results: In total, 35 patients were included (21 males, 14 females). Eight patients were treated for extra-renal malignancies. The mean V₅ of the ipsilateral kidney was 70.0 ±42.4 ml equaling to 44.9% parenchymal volume. After renal treatment, V₅ renal volume was 77.8 ±42.2 ml (48.7%) compared with 44.0 ±33.0 ml (32.0%) after extra-renal treatment. No significant reduction in KDOQI stage after 12 months of follow-up were found. Three patients developed morphologic changes in the renal parenchyma, with only one showing a decrease in renal function after 12 months.

Conclusions: CT-guided HDR-BT is a viable treatment modality for local ablative treatment of renal and adjacent masses, with no significant reduction of the KDOQI stage as a predictor for complications of chronic kidney disease. However, larger cohorts need to be analyzed to identify vulnerable patients, as in rare cases, plain dosimetry seems insufficient to predict renal function loss after HDR-BT.