RT Journal Article SR Electronic T1 Gallium-68-NeoB PET in Breast Cancer Patients: First results from a Prospective Observational Trial JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 242084 OP 242084 VO 65 IS supplement 2 A1 Kersting, David A1 Lazaridis, Lazaros A1 Küper, Alina A1 Barbato, Francesco A1 Kümmel, Sherko A1 Welt, Anja A1 Mavroeidi, Ilektra A1 Umutlu, Lale A1 Nader, Michael A1 Fragoso Costa, Pedro A1 Hautzel, Hubertus A1 Schuler, Martin A1 Fendler, Wolfgang A1 Herrmann, Ken YR 2024 UL http://jnm.snmjournals.org/content/65/supplement_2/242084.abstract AB 242084 Introduction: PET imaging and radionuclide therapy using the gastrin-releasing peptide receptor (GRPR) antagonist NeoB can offer new theranostic options for patients with various solid tumors. 68Ga-NeoB PET can be used to identify candidates with sufficient tumor uptake for 177Lu-NeoB radionuclide therapy. Here, we use 68Ga-NeoB PET to evaluate tumor uptake in patients with breast cancer.Methods: Patients were enrolled in a prospective observational trial. PET imaging was performed after a mean of 85 min (range: 48-153) after injection of 90 MBq (33-145) of 68Ga-NeoB. 68Ga-NeoB uptake was analyzed in five anatomical categories that were derived from TNM classification (breast, lymph nodes, liver, bone, other). In any region that was NeoB-positive (defined as a region that exhibits higher uptake than local background), SUVmax and peak tumor-to-liver ratio (TLRpeak) of the hottest lesion were determined. Mean SUVmax and TLRpeak were calculated as mean of all NeoB-positive regions per patient and defined as global mean SUVmax and TLRpeak.Results: We enrolled 29 patients with breast cancer (23 ER+/HER2-, 3 ER+ or -/HER2+, 3 triple-negative; 12 with distant metastases) in this study who received a total of 36 68Ga-NeoB PET scans. We excluded 7 scans that were re-staging scans in the same individuals and scans of 3 patients that did not exhibit metabolically active tumor. 10 of these remaining 26 patients had newly diagnosed and 16 had persistent/recurrent breast cancer. 18/20 ER+/HER2- patients (90.0%), 2/3 ER+ or -/HER2+ (66.7%), and N=0/3 triple-negative patients were NeoB-positive in any region. Therefore, we focused our analysis on ER+/HER2- patients: The mean (range) global mean SUVmax and TLRpeak values were 9.6 (4.1-25.9) and 2.6 (0.6-8.6), respectively. Grouping these patients according to their mean SUVmax values showed 2/18 (11.1%) patients with very high global NeoB uptake (SUVmax≥20), 5/18 (27.8%) patients with high global NeoB uptake (SUVmax≥10), 6/18 patiens (33.3%) with intermediate global NeoB uptake (10>SUVmax≥5), and 5/18 (27.8%) with low global (5>SUVmax) NeoB uptake. In a region-based analysis in ER+/HER2- patients, 77.8% (28/36) of regions with metabolically active tumor were NeoB-positive. In these regions, mean (range) SUVmax and TLRpeak were 11.3 (1.7-44.0) and 3.4 (range: 0.4-14.9), respectively. Lymph node and distant metastases showed a trend towards higher SUVmax and TLRpeak values than local tumor. Global mean SUVmax and TLRpeak did not show a significant correlation to the level of ER expression (p=0.23/0.54).Conclusions: Patients with ER+/HER2- breast cancer showed the highest rate of NeoB-positive disease. In these patients, global uptake was larger than liver uptake in about 2/3 of patients with 1/3 of patients showing global high or very high uptake. Future evaluations are warranted to identify candidates for 177Lu-NeoB radionuclide therapy in a theranostic approach.