Die klinische Wertigkeit der 99mTc-MAG3-Szintigraphie vor Peptid-Rezeptor-Radionuklid-Therapie (PRRT) zur Prädiktion von therapieinduziertem Nierenfunktionsverlust

Peptide receptor radionuclide therapy (PRRT) is a therapy procedure for patients with neuroendocrine tumours. A radiolabeled somatostatin analogon selectively targets the tumour cells while the healthy tissue remains relatively undamaged. However the radionuclide is excreted through the kidneys, which results in more or less radiation exposure of the organ depending on the length of stay and the radiopharmacon that is used with potentially nephrotoxic consequences. Patient data of the institute for nuclear medicine of the Philipps-University Marburg was retrospectively analized to evaluate the use of 99mTc-MAG3 renal scintigraphy prior to PRRT to predict loss of renal function. 59 included patients underwent a PRRT with 177Lu-DOTATOC in the period between 2009 and 2017. Serum creatinine and eGFR were detected just before and two to four months after PRRT. In addition, both the results of 99mTc-MAG3 renal scintigraphy at baseline and some of the following results in the course of therapy were documented. Usually three cycles of PRRT were performed. Complete data sets for all three cycles were collected from a total of 35 patients. In patients who had a sufficient urine drainage without prior application of a diuretic and/or after taking a postmiction picture, there was an increase in serum creatinine of 0.03 (± 0.14) mg/dl on average and a decrease in eGFR of -2.96 (± 16.27) ml/min/1.73m². In patients who had an adequate outflow only after the application of a diuretic and/or after taking a postmiction picture, there was a median decrease in serum creatinine of -0.06 (-0.33; 0.01) mg/dl and an increase in eGFR of 4.80 (± 4.66) ml/min/1.73m² on average. With patients who did not reach an adequate outflow before their therapy started neither after application of a diuretic nor after taking a postmiction picture, a decrease in the serum creatinine of -0.06 (± 0.14) mg/dl and an increase in the eGFR of 2.33 (± 6.66) ml/min/1.73m² after three cycles of PRRT was detected. Furthermore, there was a seperation between pretherapeutic eGFR <60 vs. eGFR ≥ 60ml/min/1.73m² being performed; the development of the renal function after three cycles PRRT was detected. With pretherapeutically lower renal function, there was an average decrease in serum creatinine of -0.13 (± 0.15) mg/dl and an increase in eGFR of 5.40 (± 6.31) ml/min/1.73m². In patients with better pretherapeutic renal function an increase in serum creatinine of 0.02 (± 0.13) mg/dl and a decrease in eGFR of -2.53 (± 15.46) ml/min/1.73m² was observed. Overall, the results indicate that patients with worse pretherapeutical renal function (in the sense of delayed/insufficient drainage in 99mTc-MAG3 renal scintigraphy or eGFR < 60ml/min/1.73m²) did not suffer from greater posttherapeutic renal function losses than patients with pretherapeutically normal kidney function. Paradoxically, an improvement in the course of PRRT was found in patients with previously impaired kidney function – the reason remains unclear; possible reasons could be measures which were taken to remove drainage obstructions (medical/surgical removal of an existing prostate hyperplasia), tumour decay or better hydration of the patients. In the present data analysis, pretherapeutic renal scintigraphy was not suitable for the detection of possible patients at risk for renal function losses in the course. Its importance for this indication is doubtful due to the lack of relevance of the information obtained and the increased expenditure of time, personnel and costs compared to a determination of kidney function parameters from blood. In the event that there was a decrease in renal function within the subgroups during the course of therapy, only minor losses of renal function could be observed - despite potentially nephrotoxic therapies (e.g. chemotherapy, use of non-steroidal anti-inflammatory drugs, etc.) that were often added on. This contradicts the assumption that PRRT with 177Lu-DOTATOC leads to great renal function losses provided that nephroprotection is performed.