Gastrin-releasing peptide receptor antagonist [Ga-68]RM2 PET/CT for staging of pre-treated, metastasized breast cancer

Ziel/Aim Positron emission tomography (PET)/computed tomography (CT) using the gastrin-releasing peptide receptor antagonist [Ga-68]RM2 has shown to be a promising imaging method for primary breast cancer (BC) with positive estrogen receptor (ER) status. This study assessed tumor visualization by [Ga-68]RM2 PET/CT in patients with pre-treated ER-positive BC and suspected metastases.

Methodik/Methods This retrospective pilot study included eight female patients with initial ER-positive, pre-treated BC who underwent [Ga-68]RM2 PET/CT. Most of these patients (7 of 8; 88%) were still treated with or had received endocrine therapy. [Ga-68]RM2 PET/CTs were visually analysed by two nuclear medicine specialists in consensus, using current CT, [F-18]Fluoro-2-deoxy-D-glucose PET and/or magnetic resonance imaging as a reference. Tumor manifestations were rated qualitatively (i.e. RM2-positive or RM2-negative), and quantitatively using the maximum standardized uptake value (SUV_max). SUV_max values were compared between the two subgroups (RM2-positive vs. RM2-negative).

Ergebnisse/Results Strong RM2 binding was found in all metastatic lesions of six patients (75%), whereas tracer uptake in all metastases of two patients (25%) was rated negative. Mean SUV_max of RM2-positive metastases with the highest SUV_max per patient (in lymph node and bone metastases; 15.8±15.1 range: 3.7 – 47.8) was higher than mean SUV_max of the RM2-negative metastases with the highest SUV_max per patient (in bone metastases; 1.6±0.1, range 1.5 – 1.7).

Schlussfolgerungen/Conclusions Our data suggest that RM2 binding is maintained in the majority of patients with advanced disease stage of pre-treated ER-positive BC. Thus, [Ga-68]RM2 PET/CT could support treatment decision in these patients, radiotherapy planning in oligometastatic patients or selection of patients for RM2 radioligand therapy.

 

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Publication History

Article published online:
14 April 2022