Diagnostic performance and safety of NMK36 (trans-1-amino-3-[18F]fluorocyclobutanecarboxylic acid)-PET/CT in primary prostate cancer: multicenter Phase IIb clinical trial

Abstract

Objective: We performed a multicenter Phase IIb clinical trial of NMK36, a novel amino acid analog for positron emission tomography containing trans-1-amino-3-[(18)F]fluorocyclobutanecarboxylic acid, to evaluate its safety and diagnostic performance for primary prostate cancer.

Methods: Sixty-eight subjects with primary prostate cancer scheduled for radical prostatectomy or hormone therapy underwent whole-body positron emission tomography/computed tomography after injection of NMK36. The diagnostic performances of NMK36-positron emission tomography/computed tomography were evaluated for (i) regional lymph node metastasis: comparison with contrast-enhanced computed tomography under setting reference standard (histopathology or 6-month follow-up), (ii) bone metastasis: concordance rate with conventional imaging (combination of bone scintigraphy and contrast-enhanced computed tomography) and (iii) primary lesion: comparison with histopathological findings.

Results: The accuracy of NMK36-positron emission tomography/computed tomography and contrast-enhanced computed tomography for regional lymph node metastasis were 85.5 and 87.3%, respectively. NMK36-positron emission tomography/computed tomography showed positive findings for regional lymph nodes with short-axis diameters of 5-9 mm at 23 regions in 13 patients of hormone therapy cohort, but they were not confirmed with reference standard in this study. The concordance rate of NMK36-positron emission tomography/computed tomography with conventional imaging for bone metastases was 83.3%, and seven patients had positive findings only by NMK36-positron emission tomography/computed tomography. The sensitivity and specificity of NMK36-positron emission tomography/computed tomography for primary lesion in six-segment analysis was 92.5 and 90.1%, respectively. Seven of non-serious adverse events were observed in six patients.

Conclusions: This study showed the comparable diagnostic performance of NMK36-positron emission tomography/computed tomography compared with conventional imaging. Some lesions of lymph node and bone were positive solely by NMK36-positron emission tomography/computed tomography, which needs to be confirmed with reference standard in future study to evaluate the usefulness of NMK36-positron emission tomography/computed tomography in staging prostate cancer.

Keywords: NMK36; anti-[18F]FACBC; clinical trial; positron emission tomography; prostate cancer.