Renal Function after Radioligand Treatment with 177Lu-PSMA-617

1279 Purpose: Kidneys are exposed to continuous low dose radiation during radioligand therapy with 177Lu-PSMA-617 (Lu-RLT) due to excretion of the ligand and specific binding. This may result in glomerular damage and gradual renal function loss. This study is to define the extent and potential risk factors of renal impairment in patients with metastatic castration-resistant prostate cancer (mCRPC) undergoing Lu-RLT using serial eGFR measurements driven from serum creatinine levels. Methods: 105 patients received 4 ± 1 cycles of Lu-RLT with 6.5 ± 1.4 GBq 177Lu per cycle, resulting in a mean cumulative activity of 27 ± 13 GBq and a total renal radiation dose of 13 ± 8 Gy. eGFR was measured for a median of 6 ± 4 times per patient. Yearly change in eGFR was calculated using linear curve fit. Common Terminology Criteria for Adverse Events (CTCAE) v5.0 was used to classify renal toxicity. Correlation of eGFR reduction and potential risk factors like renal impairment prior to Lu-RLT, diabetes mellitus, hypertension, previous chemotherapy and cumulated administered dose was assessed using nonparametric testing. Results: Alterations in eGFR differed widely among the patients during the follow-up period of 13 ± 9 months. 57 patients (54 %) experienced a mild (2-10 ml/min/m2 per year) and 35 patients (33 %) a significant (> 10 ml/min/m2 per year) decline of eGFR. In 18 patients, on the other hand, eGFR increased > 10 ml/min/m2 per year. Mean eGFR of the cohort decreased 4.5 ± 26 ml/min/m2 per year from 83 ± 19 ml/min/m2 at baseline to 72 ± 21 ml/min/m2. 58 patients showed renal impairment of grade I (n=30) or II (n=28) subsequent to the treatment. 3 patients developed postrenal (sub)acute kidney injury and significant renal function loss (grade 3) due to progressive bladder infiltration and subsequent ureteral stenosis. No radiation induced nephrotoxicity of grade 3/4 was observed. However, cumulated renal dose was significantly correlated with renal function decline per year (p 0.05). Conclusions: Slight reduction in renal function may be expected in patients undergoing radioligand therapy with 177Lu-PSMA-617 and correlates with cumulative doses. Acute kidney injury was observed only in a small number of cases with subrenal obstruction. Figure: Prostate cancer with Tumor infiltration of the bladder causing postrenal acute kidney injury.