Clinical evaluation of [68Ga]Ga-DATA-TOC in comparison to [68Ga]Ga-DOTA-TOC in patients with neuroendocrine tumours

Abstract

Introduction: [⁶⁸Ga]Ga-DATA-TOC is a new radiolabelled somatostatin-analogue for positron emission tomography (PET) imaging of neuroendocrine tumours. Its advantage over DOTA-conjugated compounds is the possibility for high-efficiency labelling with gallium-68 quickly at room temperature with high reliability and without the need for product purification, which enables the development of an instant kit-type labelling method. We evaluated its imaging characteristics in patients with neuroendocrine tumours in comparison to [⁶⁸Ga]Ga-DOTA-TOC.

Methods: 19 patients imaged with [⁶⁸Ga]Ga-DATA-TOC were retrospectively analysed and uptake in normal tissues was compared with a group of 19 patients imaged with [⁶⁸Ga]Ga-DOTA-TOC. 10 patients imaged with [⁶⁸Ga]Ga-DATA-TOC had a history of [⁶⁸Ga]Ga-DOTA-TOC imaging before and were additionally analysed to obtain biodistribution data of both tracers in the same patients. In 5 patients showing stable disease between both examinations, tumour uptake, lesion detectability and lesion conspicuity of both tracers were evaluated.

Results: Uptake of [⁶⁸Ga]Ga-DATA-TOC in normal organs with expression of the somatostatin receptor was 25-47% lower compared to [⁶⁸Ga]Ga-DOTA-TOC. Background of [⁶⁸Ga]Ga-DATA-TOC was 40-41% lower in the liver. A higher retention of [⁶⁸Ga]Ga-DATA-TOC was observed in the blood (up to 67%) and in the lungs (up to 44%). Tumour uptake (SUV) was 22-31% lower for [⁶⁸Ga]Ga-DATA-TOC. However, no significant differences were observed for tumour-to-background ratios and lesion detectability. Regarding liver metastases, [⁶⁸Ga]Ga-DATA-TOC uptake (SUV) reached 69-73% of [⁶⁸Ga]Ga-DOTA-TOC uptake, but tumour-to-background ratios of [⁶⁸Ga]Ga-DATA-TOC were 105-110% of [⁶⁸Ga]Ga-DOTA-TOC ratios. CONCLUSIONS, ADVANCES IN KNOWLEDGE AND IMPLICATIONS FOR PATIENT CARE: We demonstrated the feasibility of the new PET tracer [⁶⁸Ga]Ga-DATA-TOC for imaging of patients with neuroendocrine tumours, showing a comparable performance to [⁶⁸Ga]Ga-DOTA-TOC. [⁶⁸Ga]Ga-DATA-TOC has the potential for development of an instant kit-type labelling method at room temperature similar to ^99mTc-labelled radiopharmaceuticals, which might help to increase the availability of ⁶⁸Ga-labelled somatostatin analogues for clinical routine use.

Keywords: Gallium-68; Instant kit-type labelling; Neuroendocrine tumours (NET); PET/CT; Somatostatin receptor (SSTR).