GMP-compliant production of [68Ga]Ga-NeoB for positron emission tomography imaging of patients with gastrointestinal stromal tumor

Background

[⁶⁸Ga]Ga-NeoB is a novel DOTA-coupled Gastrin Releasing Peptide Receptor (GRPR) antagonist with high affinity for GRPR and good in vivo stability. This study aimed at (1) the translation of preclinical results to the clinics and establish the preparation of [⁶⁸Ga]Ga-NeoB using a GMP conform kit approach and a licensed ⁶⁸Ge/⁶⁸Ga generator and (2) to explore the application of [⁶⁸Ga]Ga-NeoB in patients with gastrointestinal stromal tumors (GIST) before and/or after interventional treatment (selective internal radiotherapy, irreversible electroporation, microwave ablation).

Results

Validation of the production and quality control of [⁶⁸Ga]Ga-NeoB for patient use had to be performed before starting the GMP production. Six independent batches of [⁶⁸Ga]Ga-NeoB were produced, all met the quality and sterility criteria and yielded 712 ± 73 MBq of the radiotracer in a radiochemical purity of > 95% and a molar activity of 14.2 ± 1.5 GBq/μmol within 20 min synthesis time and additional 20 min quality control. Three patients (2 females, 1 male, 51–77 yrs. of age) with progressive gastrointestinal stromal tumor metastases in the liver or peritoneum not responsive to standard tyrosine kinase inhibitor therapy underwent both [⁶⁸Ga]Ga-NeoB scans prior and after interventional therapy. Radiosynthesis of ⁶⁸Ga-NeoB was performed using a kit approach under GMP conditions. No specific patient preparation such as fasting or hydration was required for [⁶⁸Ga]Ga-NeoB PET/CT imaging. Contrast-enhanced PET/CT studies were performed. A delayed, second abdominal image after the administration of the of [⁶⁸Ga]Ga-NeoB was acquired at 120 min post injection.

Conclusions

A fully GMP compliant kit preparation of [⁶⁸Ga]Ga-NeoB enabling the routine production of the tracer under GMP conditions was established for clinical routine PET/CT imaging of patients with metastatic GIST and proved to adequately visualize tumor deposits in the abdomen expressing GRPR. Patients could benefit from additional information derived from [⁶⁸Ga]Ga-NeoB diagnosis to assess the presence of GRPR in the tumor tissue and monitor antitumor treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41181-021-00137-w.

Surgical Management of Metastatic Gastrointestinal Stromal Tumors

OPINION STATEMENT

Treatment with the tyrosine kinase inhibitor (TKI), imatinib is the standard first-line treatment for metastatic gastrointestinal stromal tumors (GISTs). Unfortunately, acquired c-kit mutations cause secondary resistance to imatinib in a median of 18-24 months. Sunitinib and regorafenib are multi-kinase inhibitors that can be used as second-line or third-line therapy in imatinib-resistant or -intolerant GISTs, respectively. Ripretinib (a switch-control tyrosine kinase inhibitor) has recently been approved for fourth-line treatment in metastatic GIST. The TKI avapritinib has been approved for metastatic GIST harboring the imatinib-resistant PDGFRA exon 18 mutation. Although TKI therapies have revolutionized the treatment of metastatic GISTs, they cannot cure metastatic GISTs. Therefore, cytoreductive surgery is of considerable interest and has been accordingly investigated. Retrospective non-randomized studies demonstrated the feasibility and safety of continuous TKI therapy and surgical resection. Most studies demonstrate response to TKI therapy, completeness of resection, extent of disease, and surgical complexity as predictors of outcomes. Most TKIs can be stopped shortly before surgery and restarted shortly after. There is no known survival benefit from debulking operations or R2 resections and this should not be considered. However, debulking/palliative surgery may be necessary for patients with complications of hemorrhage, pain, or intestinal obstruction. SDH-deficient GISTs have an indolent natural history despite metastatic disease and may be another uncommon subgroup that would benefit from surgical debulking (R2 resection). At the time of operation, care should be taken to avoid tumor rupture. After surgical resection, patients should resume tyrosine kinase inhibitor (TKI) therapy as soon as possible and be monitored for disease progression. In all patients with metastatic GIST, the decision to pursue metastasectomy for GIST should be made in a multidisciplinary setting and be individualized according to patient age, comorbidities, functional status, symptoms, mutation status, extent of disease, completeness of resection, TKI response, and goals of the patient.

The management of metastatic GIST: current standard and investigational therapeutics

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract. The majority of GISTs harbor gain of function mutations in either KIT or PDGFRα. Determination of the GIST molecular subtype upon diagnosis is important because this information informs therapeutic decisions in both the adjuvant and metastatic setting. The management of GIST was revolutionized by the introduction of imatinib, a KIT inhibitor, which has become the standard first line treatment for metastatic GIST. However, despite a clinical benefit rate of 80%, the majority of patients with GIST experience disease progression after 2-3 years of imatinib therapy. Second and third line options include sunitinib and regorafenib, respectively, and yield low response rates and limited clinical benefit. There have been recent FDA approvals for GIST including ripretinib in the fourth-line setting and avapritinib for PDGFRA exon 18-mutant GIST. This article aims to review the optimal treatment approach for the management of patients with advanced GIST. It examines the standard treatment options available but also explores the novel treatment approaches in the setting of imatinib refractory GIST.

Hepatectomy for liver metastasis from gastrointestinal stromal tumor in the era of imatinib mesylate: a case series study

The prognosis of metastatic gastrointestinal stromal tumor (GIST) has improved since the introduction of imatinib mesylate; however, acquired resistance has been reported, so alternative treatment option is needed. We evaluated the efficacy of hepatectomy for metastatic GIST. Six patients with liver metastases from GIST underwent hepatectomy. Four were treated with imatinib mesylate before hepatectomy, and all the patients were treated with imatinib mesylate after hepatectomy. Patients were followed-up for a mean duration of 113.5 months after hepatectomy. Complete resection was accomplished in four patients, with incomplete resection performed in the remaining two patients due to peritoneal dissemination. One patient with incomplete resection died 10 months after surgery. One patient with complete resection has survived without disease progression since initial hepatectomy. The remaining four patients with progressive disease during imatinib mesylate treatment developed tumor recurrence and three of them underwent a second hepatectomy. These three patients underwent complete resection during repeat surgery. In total, three patients died during the follow-up period, all of whom had tumors of small intestine origin. Primary tumor site (small intestine vs. others) was identified as a risk factor of mortality (P = 0.02). Although not statistically significant, there was a trend toward better outcomes in patients with exon 11 mutations. Surgical resection for metastatic GIST was shown to be effective and needed to achieve a better prognosis. Repeat hepatectomy demonstrated efficacy in selected patients. Hepatectomy should be considered based on tumor characteristics such as primary tumor site and c-KIT mutation status.

Pazopanib in metastatic multiply treated progressive gastrointestinal stromal tumors: feasible and efficacious

BACKGROUND

A median progression free survival (PFS) of 18-20 months and median overall survival (OS) of 51-57 months can be achieved with the use of imatinib, in metastatic or advanced gastrointestinal stromal tumor (GIST). Sunitinib and regorafenib are approved options for patients progressing on imatinib, but with markedly decreased survival. pazopanib is a broad spectrum TKI targeting KIT, PDGFR and VEGFR receptors and has shown promising activity in phase 2 trials in GIST.

METHODS

All patients who received pazopanib for GIST between March 2014 and September 2015 in our institution were reviewed. Patients were assessed for response with CT or PET CT scans. Patients continued pazopanib until progression or unacceptable toxicity. Survival was evaluated by Kaplan Meier product method.

RESULTS

A total of 11 consecutive patients were included in our study. Median duration of follow up was seven months. The median lines of prior therapy was 2 [1-5]. Partial response (PR) was observed in seven patients and two had stable disease (SD). Two patients died within one month of start of pazopanib. Five of ten patients had progressed during the study with eight patients still alive. The median PFS was 11.9 months and the median OS was not reached. Common adverse events seen were hand-foot-syndrome (HFS) in four patients, anemia in four patients and fatigue in three patients. Grade 3/4 adverse events were uncommon. Three patients required dose modification of pazopanib.

CONCLUSIONS

Pazopanib is a reasonably efficacious well tolerated TKI and can be explored as a treatment option in advanced GIST that has progressed on imatinib.