Renal function studies using 99mTc-MAG3: pharmacokinetics and slope clearance determination

Therapeutic response and side effects of repeated radioligand therapy with 177Lu-PSMA-DKFZ-617 of castrate-resistant metastatic prostate cancer

Prostate-specific membrane antigen (PSMA) is highly expressed on prostate epithelial cells and strongly up-regulated in prostate cancer (PC), making it an optimal target for the treatment of metastasized PC. Radioligand therapy (RLT) with ¹⁷⁷Lu-PSMA-DKFZ-617 (Lu-PSMA) is a targeted therapy for metastatic PC. In this study, we retrospectively analyzed the side effects and the response rate of 24 hormone and/or chemorefractory PC patients with a mean age of 75.2 years (range: 64–82) with distant metastases and progressive disease according to the PSA level, who were treated with Lu-PSMA. Median PSA was 522 ng/ml (range: 17–2360). Forty-six cycles of Lu-PSMA were performed. Of the 24 patients, 22 received two cycles. Eight weeks after the first cycle of Lu-PSMA therapy 79.1% experienced a decline in PSA level. Eight weeks after the second cycle of Lu-PSMA therapy 68.2% experienced a decline in PSA relative to the baseline value. Apart from two cases of grade 3 anemia, there was no relevant hemato- or nephrotoxicity (grade 3 or 4). These results confirmed that Lu-PSMA is a safe treatment option for metastatic PC patients and has a low toxicity profile. A positive response to therapy in terms of decline in PSA occurs in about 70% of patients.

Early side effects and first results of radioligand therapy with (177)Lu-DKFZ-617 PSMA of castrate-resistant metastatic prostate cancer: a two-centre study

Background

Radioligand therapy (RLT) with ¹⁷⁷Lu-DKFZ-617 PSMA (Lu-PSMA) (prostate-specific membrane antigen) is a novel targeted therapy of metastatic prostate cancer. We analysed retrospectively the early side effects and the response rate in the first patients, who received a therapy with Lu-PSMA in our departments.

Methods

RLT was performed in ten hormone- and/or chemo-refractory patients with distant metastases and progressive disease (mean age 73.5 years). ⁶⁸Ga-PSMA HBED-CC PET/CT was performed in all patients prior to RLT. The median PSA level prior to the therapy was 298.5 ng/ml (range 5–853 ng/ml). All patients received CBC, renal and liver function tests the day before and 2 days after application (mean administered activity 5.6 GBq, range 4.1–6.1 GBq), followed by further tests every 2 weeks. All patients were contacted by telephone every week regarding side effects or any positive and negative changes.

Results

Eight weeks after the therapy, seven patients (70 %) experienced a PSA decline, of whom six experienced more than 30 % and five more than 50 %. Three patients showed a progressive disease according to the PSA increase. No patient experienced any side effects immediately after injection of Lu-PSMA. Relevant hematotoxicity (grade 3 or 4) occurred 7 weeks after the administration in just one patient. The same patient showed a leucopenia grade 2. Two patients showed a disturbance of only 1 hematologic cell line, whereas one patient showed a reduction of grades 1 and 2 in leucocytes and thrombocytes, respectively. Six patients did not show any hematotoxicity during the 8 weeks after therapy. There was no relevant nephrotoxicity (grade 3 or 4).

Conclusions

Our initial results indicate that RLT with Lu-PSMA is safe and seems to have low early side-effect profile. A relevant PSA decline was detected in 70 % of patients.

Assessment of renal graft function by perioperative monitoring of cortical microcirculation in kidney transplantation

BACKGROUND

We evaluated the significance of perioperative cortical microperfusion for graft function and long-term prognosis after renal allotransplantation. Thermodiffusion technology was clinically applied for the first time, after previous validation for perfusion monitoring of the renal cortex in pigs.

METHODS

A thermodiffusion probe was inserted into the renal cortex in 30 transplant recipients after graft reperfusion. Real-time measurements were recorded until the end of the operation. In 14 patients perfusion was measured daily until postoperative day 7. Microcirculation was correlated to serum creatinine level, scintigraphic findings, and long-term outcome.

RESULTS

In primary graft function, intraoperative perfusion was 85+/-7 mL/100 g per min compared with significantly lower values in cases with subsequent graft dysfunction. The best discrimination was defined for a level of 70 mL/100 g per min with a positive predictive value of 88% for detection of good graft function and 86% for nonfunction. Intraoperative perfusion was significantly different in patients with normal grafts, delayed function, and graft loss. Postoperatively, lower perfusion was found in acute tubular necrosis; a significant correlation could be noted between microcirculation and perfusion index measured by nuclear scanning (r=0.78, P<0.01). Living-related grafts were characterized by higher intraoperative perfusion and superior graft quality.

CONCLUSION

Thermodiffusion could be clinically applicable for the perioperative monitoring of renal graft perfusion. Intraoperative reduction of cortical microcirculation has a high predictive value with respect to detection of delayed renal function. Postoperatively, impaired renal microperfusion is associated with acute tubular necrosis. Living-related donor grafts show less microcirculatory alteration than cadaveric kidneys.

Delayed graft function is characterized by reduced functional mass measured by (99m)Technetium-mercaptoacetyltriglycine renography

BACKGROUND

The mechanism that underlies delayed graft function (DGF) is still poorly defined. Previous studies using tubular function tests have shown that postischemic injury to the renal transplants results in profound impairment of paraimmunohippurate (PAH) extraction through the tubules.

METHODS

Using (99m)Technetium-mercaptoacetyltriglycine ((99m)Tc-MAG3) renography and tubular function slope (TFS), a study of the tubular uptake of (99m)Tc-MAG3 was undertaken in a prospective study of renal transplant recipients with immediate graft function (IGF) and those with DGF.

RESULTS

A total of 37 consecutive recipients of a cadaveric graft and 5 kidneys from living donors was evaluated within 48 hours after transplantation and in week 2, months 3 and 6, and 3 years after transplantation. In addition to the protocol scans, recipients with DGF were examined every other day until function was resumed. Repeated measurement two-way analysis of variance and a change point analysis were performed to determine the difference in the follow-up of TFS values between the two groups. Fourteen patients were classified as having DGF and 28 immediate graft function. In the DGF group, the initial TFS value was significantly lower than in the immediate graft function group (0.54 [+/-0.01] and 1.75 [+/-0.16], respectively; P=0.002), a difference that persisted for up to 3 years. Change point analysis revealed that the postischemic tubular excretion improved with time in both groups in the first 3 to 4 weeks, but both groups remained different up to 3 years after transplantation. Multivariate analysis revealed that only the cold ischemic time was an independent risk factor for a low TFS value. After the initial recovery from postischemic injury, the TFS may be used as a marker for functional renal mass.

CONCLUSION

We propose that the tubular defect in DGF, as defined by (99m)Tc-MAG3 renography, is irreversible and may be a marker of initial graft function.

Quantitative scintigraphic parameters for the assessment of renal transplant patients

Radionuclide renal diagnostic studies play an important role in assessing renal allograft function especially in the early post transplant period. In the last two decades various quantitative parameters have been derived from the radionuclide renogram to facilitate and confirm the changes in perfusion and/or function of the kidney allograft. In this review article we discuss the quantitative parameters that have been used to assess graft condition with emphasis on the early post-operative period. These quantitative methods were divided into parameters used for assessing renal graft perfusion and parameters used for evaluating parenchymal function. The blood flow in renal transplants can be quantified by measuring (a) the rate of activity appearance in the kidney graft; (b) the ratio of the integral activity under the transplanted kidney and arterial curves e.g. Hilson's perfusion index and Kircher's kidney/aortic ratio; (c) calculating the renal vascular transit time by deconvolution analysis. The literature overview on these parameters showed us that they have some practical disadvantages of requiring high quality bolus injection and numerical variations related to changes in the site and size of regions of interest. In addition, the perfusion parameter values suffer from significant overlap when various graft pathologies coexist. Quantitative evaluation of the graft parenchymal extraction and excretion was assessed by parameters derived from 123I/131I-OIH, 99mTc-DTPA or 99mTc-MAG3 renograms. We review in this article a number of parenchymal parameters which include (1) plasma clearance methods like glomerular filtration rate (GFR) and effective renal plasma flow (ERPF); (2) renal transit times such as parenchymal mean transit time, Tmax, T1/2; (3) parenchymal uptake and excretion indices as the accumulation index, graft uptake capacity at 2 and 10 min, excretion index and elimination index. These indices, however, are non-specific and far from defining a specific cause for graft parenchymal dysfunction. In conclusion, despite that the literature is replete with mathematical strategies for quantitating perfusion and parenchymal functions, none of these have enough diagnostic power for specific diagnosis of graft dysfunction. In addition, no universal agreement on the use of certain quantitation parameters in transplant patients has been reached.