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Prospective Comparison of 68Ga-NeoB and 68Ga-PSMA-R2 PET/MRI in Patients with Biochemically Recurrent Prostate Cancer - Beyond the Abstract

Managing biochemically recurrent prostate cancer is challenging when conventional imaging like CT and MRI fails to identify recurrent disease, particularly at low PSA levels. Treatment can be given only blindly as radiation therapy to the pelvis or systemic androgen deprivation therapy. Our study assessed the feasibility, safety, and diagnostic performance of 68Ga-NeoB and 68Ga-PSMA-R2 PET/MRI in this select patient cohort.

These two novel radiopharmaceuticals were developed for theragnostic use, i.e. molecular imaging and treatment. Each targets a different biological marker: 68Ga-NeoB targets the gastrin-releasing peptide receptor (GRPR) and 68Ga-PSMA-R2 targets prostate-specific membrane antigen (PSMA); both molecular markers are known to be overexpressed in prostate cancer.

Both 68Ga-NeoB and 68Ga-PSMA-R2 were feasible and safe for diagnostic imaging. 68Ga-NeoB outperformed 68Ga-PSMA-R2 PET/MRI with higher detection rates on a per-patient and per-lesion basis, particularly in detecting bone and lymph node metastases at lower PSA levels. Higher sensitivity, accuracy, and negative predictive value were seen with 68Ga-NeoB while specificity and positive predictive value were equally high for both radiopharmaceuticals.

The biodistribution of 68Ga-NeoB with improved affinity to GRPR was more favorable for theragnostic use than 68Ga-PSMA-R2, which showed overall lower tumor uptake and tumor-to-background ratio. Although PSMA-targeted PET imaging is the most commonly and widely used, GRPR-targeted PET imaging presents a complementary or alternative option. Prostate cancer has a heterogeneous biology, therefore, the more biological targets we have, the better care we can provide for our patients.

Written by: Heying Duan,1 Hong Song,1 Guido A Davidzon,1 Farshad Moradi,1 Tie Liang,1 Andreas Loening,2 Shreyas Vasanawala,2 Andrei Iagaru,1

  1. Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Stanford University, Stanford, California
  2. Division of Body MRI, Department of Radiology, Stanford University, Stanford, California.

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