Results from extended lymphadenectomies with [111In]PSMA-617 for intraoperative detection of PSMA-PET/CT-positive nodal metastatic prostate cancer

CITATION: Jilg, C. A., et al. 2020. Results from extended lymphadenectomies with [111In]PSMA-617 for intraoperative detection of PSMA-PET/CT-positive nodal metastatic prostate cancer. EJNMMI Research, 10:17, doi:10.1186/s13550-020-0598-2.The original publication is available at https://ejnmmires.springeropen.comPurpose: Identification of suspicious PSMA-PET/CT-positive lymph node (LN) metastases (LNM) from prostate cancer (PCa) during lymphadenectomy (LA) is challenging. We evaluated an 111In-labelled PSMA ligand (DKFZ-617, referred to as [111In]PSMA-617) as a γ-emitting tracer for intraoperative γ-probe application for resected tissue samples in PCa patients. Forty-eight hours prior to LA, [111In]PSMA-617 was administered intravenously in 23 patients with suspected LNM on PSMA-PET/CT (n = 21 with biochemical relapse, n = 2 at primary therapy). Resected tissue samples (LN, LNM and fibrofatty tissue) were measured ex situ by a γ-probe expressed as counts per second (CPSnorm). [111In]PSMA-617 tissue sample uptake was measured by a germanium detector for verification and calculated as %IAlbm (percent injected activity per kilogram lean body mass at time of surgery). Based on a clinical requirement for a specificity > 95%, thresholds for both ex situ measurements were chosen accordingly. Correlation of the results from PET/CT, γ-probe and germanium detector with histopathology was done. Results: Eight hundred sixty-four LNs (197 LNM) were removed from 275 subregions in 23 patients, on average 8.6 ± 14.9 LNM per patient. One hundred four of 275 tissue samples showed cancer. Median γ-probe and germanium detector results were significantly different between tumour-affected (33.5 CPSnorm, 0.71 %IAlbm) and tumour-free subregions (3.0 CPSnorm, 0.03 %IAlbm) (each p value 23) and germanium detector cut-off (%IAlbm > 0.27), 64 and 74 true-positive and 158 true-negative samples for both measurements were identified. Thirty-nine and 30 false-negative and 6 and 5 false-positive tissue samples were identified by γ-probe and germanium detector measurements. Conclusion: [111In]PSMA-617 application for LA is feasible in terms of an intraoperative real-time measurement with a γ-probe for detection of tumour-affected tissue samples. γ-probe results can be confirmed by precise germanium detector measurements and were significantly different between tumour-affected and tumour-free samples.https://ejnmmires.springeropen.com/articles/10.1186/s13550-020-0598-2Publisher's versio

Performance of 111In-labelled PSMA ligand in patients with nodal metastatic prostate cancer: correlation between tracer uptake and histopathology from lymphadenectomy

PURPOSE: Intraoperative identification of lymph node (LN) metastases (LNM) detected on preoperative PSMA PET/CT may be facilitated by PSMA radioguided surgery with the use of a gamma probe. We evaluated the uptake of 111In-labelled PSMA ligand DKFZ-617 (referred to as 111In-PSMA-617) in unaffected LN and LNM at the level of single LN. METHODS: Six patients with prostate cancer (PCa) with suspicion of LNM on preoperative PSMA PET/CT underwent 111In-PSMA-617-guided lymphadenectomy (LA; four salvage LA and two primary LA). 111In-PSMA-617 (109 ± 5 MBq). was injected Intravenously 48 h prior to surgery Template LAs were performed in small subregions: common, external, obturator and internal iliac vessels, and presacral and retroperitoneal subregions (n = 4). Samples from each subregion were isolated aiming at the level of single LN. Uptake was measured ex situ using a germanium detector. Receiver operating characteristic (ROC) analysis was performed based on 111In-PSMA-617 uptake expressed as standardized uptake values normalized to lean body mass (SUL). RESULTS: Overall 310 LN (mean 52 ± 19.7) were removed from 74 subregions (mean 12 ± 3.7). Of the 310 LN, 35 turned out to be LNM on histopathology. Separation of the samples from all subregions resulted in 318 single specimens: 182 PCa-negative LN samples with 275 LN, 35 single LNM samples, 3 non-nodal PCa tissue samples and 98 fibrofatty tissue samples. The median SULs of nonaffected LN (0.16) and affected LN (13.2) were significantly different (p < 0.0001). Based on 38 tumour-containing and 182 tumour-free specimens, ROC analysis revealed an area under the curve of 0.976 (95% CI 0.95-1.00, p < 0.0001). Using a SUL cut-off value of 1.136, sensitivity, specificity, positive predictive value, negative predictive value and accuracy in discriminating affected from nonaffected LN were 92.1% (35/38), 98.9% (180/182), 94.6% (35/37), 98.4% (180/183) and 97.7% (215/220), respectively. CONCLUSION: Ex situ analysis at the level of single LN showed that 111In-PSMA-617 had excellent ability to discriminate between affected and nonaffected LN in our patients with PCa. This tracer characteristic is a prerequisite for in vivo real-time measurements during surgery

The somatostatin receptor 2 antagonist ⁶⁴Cu-NODAGA-JR11 outperforms ⁶⁴Cu-DOTA-TATE in a mouse xenograft model

<div><p>Copper-64 is an attractive radionuclide for PET imaging and is frequently used in clinical applications. The aim of this study was to perform a side-by-side comparison of the <i>in vitro</i> and <i>in vivo</i> performance of ⁶⁴Cu-NODAGA-JR11 (NODAGA = 1,4,7-triazacyclononane,1-glutaric acid,4,7-acetic acid, JR11 = p-Cl-Phe-cyclo(D-Cys-Aph(Hor)-D-Aph(cbm)-Lys-Thr-Cys)D-Tyr-NH₂), a somatostatin receptor 2 antagonist, with the clinically used sst2 agonist ⁶⁴Cu-DOTA-TATE ((TATE = D-Phe-cyclo(Cys-Tyr-D-Trp-Lys-Thr-Cys)Thr). <i>In vitro</i> studies demonstrated K_d values of 5.7±0.95 nM (Bmax = 4.1±0.18 nM) for the antagonist ^64/natCu-NODAGA-JR11 and 20.1±4.4. nM (Bmax = 0.48±0.18 nM) for the agonist ^64/natCu-DOTA-TATE. Cell uptake studies showed the expected differences between agonists and antagonists. Whereas ⁶⁴Cu-DOTA-TATE (the agonist) showed very effective internalization in the cell culture assay (with 50% internalized at 4 hours post-peptide addition under the given experimental conditions), ⁶⁴Cu-NODAGA-JR11 (the antagonist) showed little internalization but strong receptor-mediated uptake at the cell membrane. Biodistribution studies of ⁶⁴Cu-NODAGA-JR11 showed rapid blood clearance and tumor uptake with increasing tumor-to-relevant organ ratios within the first 4 hours and in some cases, 24 hours, respectively. The tumor washout was slow or non-existent in the first 4 hours, whereas the kidney washout was very efficient, leading to high and increasing tumor-to-kidney ratios over time. Specificity of tumor uptake was proven by co-injection of high excess of non-radiolabeled peptide, which led to >80% tumor blocking. ⁶⁴Cu-DOTA-TATE showed less favorable pharmacokinetics, with the exception of lower kidney uptake. Blood clearance was distinctly slower and persistent higher blood values were found at 24 hours. Uptake in the liver and lung was relatively high and also persistent. The tumor uptake was specific and similar to that of ⁶⁴Cu-NODAGA-JR11 at 1 h, but release from the tumor was very fast, particularly between 4 and 24 hours. Tumor-to-normal organ ratios were distinctly lower after 1 hour. This is indicative of insufficient <i>in vivo</i> stability. PET studies of ⁶⁴Cu-NODAGA-JR11 reflected the biodistribution data with nicely delineated tumor and low background. ⁶⁴Cu-NODAGA-JR11 shows promising pharmacokinetic properties for further translation into the clinic.</p></div

Saturation binding of ^64/natCu-DOTA-TATE onto HEK-hsst2 cells.

<p>The cells were incubated with increasing concentrations of ⁶⁴Cu-DOTA-TATE (range 0.5–90 nM) for 2 hours at +4ºC.</p

Mass dependence of ⁶⁴Cu-NODAGA-JR11 biodistribution in mice bearing HEK-hsst2 xenografts 1 hour p.i.

<p>Mass dependence of ⁶⁴Cu-NODAGA-JR11 biodistribution in mice bearing HEK-hsst2 xenografts 1 hour p.i.</p

Saturation binding of ⁶⁴Cu-NODAGA-JR11 to HEK-hsst2 cells.

<p>The cells were incubated with increasing concentrations of ^64/natCu-NODAGA-JR11 (range 0.5–75 nM) for 2 hours at +4ºC.</p

Chemical structures of NODAGA-JR11 and DOTA-TATE.

<p>Chemical structures of NODAGA-JR11 and DOTA-TATE.</p

Internalization, binding, and dissociation of ⁶⁴Cu-NODAGA-JR11.

<p>HEK-hsst2 cells were incubated with ⁶⁴Cu-NODAGA-JR11 at +4°C for 120 minutes and the temperature was shifted to 37°C by adding warm media (A) or media containing 50 pmol of NODAGA-JR11 (B). The amount of cell-bound, internalized, and dissociated activity was determined between 0 to 120 minutes after the temperature shift.</p

Externalization kinetics of ⁶⁴Cu-DOTA-TATE in HEK-hsst2 cells.

<p>HEK-hsst2 cells were incubated with ⁶⁴Cu-DOTA-TATE for 2 hours at +37°C. The receptor-bound ligands were removed by washing with glycine buffer, pH 2.8. Cells were then incubated by adding fresh medium and the amount of externalized and internalized (retained) radioactivity in the cells was measured after 10, 20, 30, 60, and 120 minutes.</p