Validation runs for [68Ga]Ga-NeoB
The results of the validation runs are summarized in Table 1. Runs with a different buffer amount were performed to evaluate and validate the possible effect of inaccuracies during the addition by different operators. The elution of the generator was performed with 5.5 mL 0.1 M HCl (EZAG), resulting in 5.0 mL 68Ga-solution in the reaction vial and not less than 0.5 mL buffer solution (maximum 0.55 mL). In comparison to productions A (0.50 mL buffer solution) the insignificant higher amount (0.55 mL buffer solution) in productions B resulted in the same RCP using the TLC-method, but the RCP determined by HPLC demonstrated a slightly higher RCP. The production-SOP for [68Ga]Ga-NeoB has to instruct to use at minimum an amount of buffer of 0.50 mL. In conclusion, all six consecutive runs were inside of all the specifications yielding 712 ± 73 MBq of [68Ga]Ga-NeoB in a radiochemical yield of > 95%. The room conditions were proper and the devices are qualified for the production; thus the production process as carried out was demonstrated to be valid for patient production of [68Ga]Ga-NeoB.
Table 1
Results of the validation runs of [68Ga]Ga-NeoB.
Run # | batch # | | | Reaction | Quality control |
| BufferBuffer Charge | buffer [ml] | HCl* [ml] | temp. time | yield** [MBq] | pH | radionuclide purity 68Ga-content | RCP: HPLC / TLC | Sterile |
A-1 | CT00516004 F03517002 | 0.50 | 5.0 | 95.1°C 10 min | 765.2 | 3.5 | 1.13 h > 99.999% | 96.1% 99.0% | yes |
A-2 | CT00516004 F03517002 | 0.50 | 5.0 | 94.9°C 9 min | 716.0 | 3.5 | 1.12 h > 99.999% | 96.4% 98.7% | yes |
A-3 | CT00516004 F03517002 | 0.50 | 5.0 | 95.1°C 8 min | 568.0 *** | 3.4 | 1.12 h > 99.999% | 97.0% 99.9% | yes |
B-1 | CT00516004 F03517002 | 0.55 | 5.0 | 95.0°C 8 min | 745.6 | 3.8 | 1.13 h > 99.999% | 98.5% 99.2% | yes |
B-2 | CT00516004 F03517002 | 0.55 | 5.0 | 95.0°C 10 min | 756.2 | 3.8 | 1.12 h > 99.999% | 97.0% 98.5% | yes |
B-3 | CT00516004 F03517002 | 0.55 | 5.0 | 95.2°C 7 min | 722.0 | 3.7 | 1.13 h > 99.999% | 98.7% 99.4% | yes |
*: Elution volume minus 0.5 mL dead volume of the tubing
**: measured 2–5 minutes after cool down
***: second generator elution of the day (first elution 2.5 h before)
[68 Ga]Ga-NeoB: Clinical PET/CT investigations
For an implementation in clinical routine, three patients (2♀, 1♂, 51–77 a) with biopsy proven, metastatic GIST were examined with the GMP-produced [68Ga]Ga-NeoB via PET/CT for staging purposes after they had been treated by antiproliferative drug therapy (imatinib, sunitinib, regorafenib) followed by SIRT, IRE or MWA. Image acquisition, attenuation correction, fusion, reconstruction and post-processing was performed on a dedicated workstation. SUVmax was determined both on the initial whole-body and on the later focused imaging.
Patient #1 (male, 57 years old, small bowel GIST with peritoneal and progressive liver metastases after 3rd line therapy carrying an exon 11 and a 2ndary exon 17 mutation) received [18F]FDG PET/CT for staging and two of the progressive liver metastases in segment VII and segment II/III were depicted. The patient underwent subsequent SIRT therapy. Four months after therapy the patient received [68Ga]Ga-NeoB (229 MBq) for follow-up staging (Fig. 2) with low accumulation in the lesion in liver segment VII (SUVmax early of 1.4, SUVmax late of 3.3), but with persistence of the radiotracer in liver segment II/III (SUVmax early of 6.3, SUVmax late of 16.1), indicating still vital tumor tissue. Thus, the patient again underwent IRE on the left lobe (segment II/III). In comparison to the preliminary examination with [18F]FDG, two newly occurring demarcated peritoneal metastases in the right hemiabdomen with increased nuclide uptake (SUVmax early of 3.3 and 5.7, SUVmax late 6.4 and 17.9, respectively) were detected with [68Ga]Ga-NeoB. In addition, physiological distribution of [68Ga]Ga-NeoB was found in the study area. At a three-month [18F]FDG PET/CT follow-up the patient showed further progressive disease.
Patient #2 (female, 77 years old, small bowel GIST with progressive peritoneal and soft tissue metastases under third line therapy carrying an exon 11 and two different secondary mutations in exon 13) received [68Ga]Ga-NeoB (202 MBq) PET/CT for staging. A previously unknown isolated hypodense liver lesion in segment VII (SUVmax early of 11.2, SUVmax late of 16.6) was found (Fig. 3). Additionally, an abdominal wall metastasis in the left lower abdomen was found, which was not previously known from a three-month preliminary [18F]FDG PET/CT and was later proven histologically by surgical resection. In addition, physiological distribution of [68Ga]Ga-NeoB was visible in the study area. The single metastasis in liver segment VII was treated by IRE and no lesions were found by magnetic resonance imaging (MRI) follow-up 11 months later. Therefore, the patient was considered to have experienced a complete response.
Patient #3 (female, 51 years old, multiple progressive hepatic metastases of GIST of the stomach carrying a D842V mutation in PDGFRa and being pretreated as treated by SIRT and microwave ablation at previously known hepatic metastases. Three months later the patient received [68Ga]Ga-NeoB (135 MBq) PET/CT for staging (Fig. 4). An inhomogeneous, flat tracer accumulation within the uterine cavity with decrease of uptake in the temporal course (SUVmax 60 min p.i. of 26.5, SUVmax 120 min p.i. of 7.1, SUVmax 180 min p.i. of 6) was found, most likely a physiological enrichment. In addition, physiological radiopharmaceutical distribution in the study area was observed. However, there was no pathologically increased uptake of [68Ga]Ga-NeoB in the known hepatic metastatic lesions which had an unchanged morphology in comparison to the three-month previously performed [18F]FDG PET/CT. No tumor uptake and no new metastases were found in the region of interest also at later time-points indicating a stable disease. In the 120 min p.i. images, an increased nuclide uptake was found in the region of the gall bladder neck (Fig. 4b). However, after fatty eating, there was no correlation in 180 min p.i. images (Fig. 4c). An additional MRI follow-up examination six months after therapy was performed, which confirmed a stable disease.