Aim: The aim of this study is to correlate the uptake, residence time, and resulting mean absorbed dose in the kidneys with the posttherapy effect on renal function using the two most commonly used somatostatin analogs, (177)Lu-DOTATATE and (177)Lu-DOTATOC, during consecutive cycles of peptide receptor radionuclide therapy (PRRNT) in the same patient.
Methods: 22 patients with metastatic neuroendocrine tumors underwent PRRNT with (177)Lu-DOTATATE and (177)Lu-DOTATOC. Dosimetry (MIRD scheme) was performed using OLINDA software. The patients were followed up for 6-12 months with serum creatinine, BUN, tubular extraction rate (TER) using (99m)Tc-MAG3, and glomerular filtration rate (GFR) using (99m)Tc-DTPA before and after therapy. Age, hypertension, and diabetes mellitus were the associated risk factors for renal toxicity, which were taken into account.
Results: Uptake, residence time, and mean absorbed dose to the kidney were slightly, but significantly, higher for DOTATATE (actual absorbed dose 1.9-9.2 Gy) as compared with DOTATOC (dose 2.3-7.8 Gy) in 19 out of the 22 (86%) patients (p < 0.05). The tumor-to-kidney ratio was higher for DOTATOC in 23 out of 43 (53%) of the lesions analyzed; however, this difference was not statistically significant. There were no statistically significant changes in serum creatinine, BUN, TER or GFR pre and post-therapy with either DOTATATE or DOTATOC. Five of the 22 patients had mildly elevated serum creatinine after PRRNT, of whom 3 had history of hypertension, 1 had diabetes, and 1 was more than 65 years of age.
Conclusions: (177)Lu-DOTATATE and (177)Lu-DOTATOC are safe radiopharmaceuticals concerning renal toxicity. (177)Lu-DOTATOC delivers a slightly, but significantly, lower renal dose.