Diagnostic Potential of 68Ga-NeoB PET/CT with Estrogen Receptor- and Progesterone Receptor-Positive Breast Cancer Undergoing Staging or Restaging for Metastatic Disease.

Sabahi Z, Nguyen A, Wong K, Li S, Papa N, Lim E, Dear RF, Menzies AM, Boyle F, Antill Y, Kiely BE, Forster BC, Mak C, Adams D, Pugliano L, Spillane A, Sharma S, Hickey A, Poole A, Agrawal S, Khan S, Ayati N, Emmett L. Journal of Nuclear Medicine, (Mar 2025): jnumed.124.268896, doi:10.2967/jnumed.124.268896.

Abstract

Background: 18F-FDG PET/CT has low sensitivity for estrogen receptor and progesterone receptor (ER/PR)-positive breast cancer. By contrast, gastrin-releasing peptide receptor is overexpressed in ER/PR-positive breast cancer. This study assessed the diagnostic potential of 68Ga-NeoB PET/CT in staging or restaging metastatic ER/PR-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer.

Methods: Patients with ER/PR-positive and HER2-negative breast cancer with clinical suspicion for metastatic disease undergoing staging or restaging were prospectively enrolled. All patients underwent 68Ga-NeoB PET/CT, in addition to standard 18F-FDG PET/CT. ER/PR-positive and HER2-negative status was confirmed in prior biopsy samples (primary or metastatic). Conventional imaging (18F-FDG PET/CT, bone scan, and diagnostic CT) was required within 3 wk of 68Ga-NeoB PET/CT. 18F-FDG PET/CT and 68Ga-NeoB PET/CT were assessed visually and quantitatively. Visually, all scans were read masked by 2 readers, with a third reader if results were discordant.

Results: Twenty patients were enrolled, all with ER/PR-positive and HER2-negative histopathology. Of these, 75% (15/20) had lobular-subtype cancer, 40% (8/20) had suspected metastatic disease at diagnosis, and 60% (12/20) underwent restaging after systemic therapy. Overall, 75% (15/20) of the 68Ga-NeoB PET/CT scans and 65% (13/20) of the 18F-FDG PET/CT scans were positive on visual assessment. For 50% (10/20) of patients, both scans were positive, and for 10% (2/20) of patients, both scans were negative. In the staging group, 75% (6/8) of patients had positive 68Ga-NeoB PET/CT and 50% (4/8) of patients had positive 18F-FDG PET/CT. At restaging, 75% (9/12) of patients had positive 68Ga-NeoB PET/CT and 75% (9/12) of patients had positive 18F-FDG PET/CT. Sites of positive 68Ga-NeoB PET/CT and negative 18F-FDG PET/CT disease were identified in 50% (4/8) of staging patients and 42% (5/12) of restaging patients, whereas negative 68Ga-NeoB PET/CT and positive 18F-FDG PET/CT disease was found in none of the staging patients but 58% (7/12) of the restaging cohort. Of these, 71% (5/7) of patients had a reduction in their ER status in the most recent biopsy samples. Quantitatively, the median SUVmax was higher for 68Ga-NeoB PET/CT (20.5; interquartile range, 5.8-31.3) than for 18F-FDG PET/CT (7.4; interquartile range, 4.9-9.8).

Conclusion: 68Ga-NeoB PET/CT has diagnostic potential in the staging of ER/PR-positive and HER2-negative breast cancer. Further evaluation is warranted.