Abstract P5-01-01: Pretargeted immuno-PET with an anti-carcinoembryonic antigen (CEA) bispecific antibody (BsMAb) and a68Ga-labeled hapten-peptide compared to conventional imaging and FDG-PET in metastatic breast cancer patients (BC): First results

Objectives: Different imaging methods are available to detect BC recurrence, but several new noninvasive antibody imaging methods targeting membranous IGF-1R expression 1 , HER2/neu 2 or CD138 3 have been tested in BC pre-clinical trials. Today, a new generation anti-CEA x anti-HSG humanized trivalent TF2 BsMAb and 68 Ga-IMP288 HSG peptide is available with good features for immuno-PET in preclinical studies 4 . This study aimed to compare the sensitivity of anti-CEA immuno-PET/CT using pretargeted 68 Ga-IMP288 to morphological imaging and FDG-PET/CT in metastatic BC patients. Methods : Ten patients, enrolled in an optimization immuno-PET study underwent whole-body immuno-PET/CT recorded 1h and 2h after injection of 150 MBq of 68 Ga-IMP288 pretargeted by 120 nmol of TF2 injected 24h to 30h before, in addition to thoracic-abdominal-pelvic CT and FDG-PET/CT. Bone (n=5) and brain MRI (n=2) were also performed in some cases to confirm abnormalities detected by other modalities. The gold standard was determined by follow-up and a lesion detected by at least 2 imaging modalities was considered as positive. Results : Median CA15-3 was 264.1 kUI/L (31.6 to 2448) and median CEA was 48.25 µg/L (9.5 to 1359.0). A total of 537 lesions were detected by immuno-PET/CT, 247 by CT, 160 by bone MRI, and 428 by FDG-PET/CT. To date, 524 lesions were confirmed as pathologic by the gold standard: 17 in nodes, 1 in lung, 83 in liver, 418 in bone, 1 in skin, and 4 in brain. Overall sensitivity of immuno-PET was 92.8%, with 100% sensitivity for bone, liver, skin, and brain, 92.8% for nodes, and 28.6% for lung. Overall sensitivity of CT and FDG-PET/CT were 74% and 95.2%, respectively. CT and FDG-PET/CT had 54.5 and 100% sensitivity for nodes, 90 and 100 % for liver, 100 and 85.7% for lung, and 68% and 94% for bone, respectively. Bone MRI had 92.3% sensitivity. Brain lesions were only detected by immuno-PET/CT and confirmed by MRI. Median tumor SUVpeak on immuno-PET at 1h and FDG-PET/CT were 5.05 (3.52 to 24.55) and 3.3 (0.47-10.95), respectively. A 2h, median tumor SUVpeak on immuno-PET was 5.23 (3.09-34.27), 5/9 patients showing an increased tumor uptake between 1 and 2h, with no lesion being detected only at 2h. Conclusion : These results demonstrate the high accuracy of anti-CEA pretargeted immuno-PET/CT for staging BC patients, especially for bone, liver and brain evaluation. Immuno-PET allowed detection of bone lesions in eras not explored by MRI. 1. Heskamp S. J Nucl Med 2010. 2. Dijkers ECF. J Nucl Med 2009. 3. Rousseau C. EJNMMI Res. 2011. 4. Schoffelen, Mol Cancer Ther, 2010. Citation Format: Mario Campone, Aurore Rauscher, Alain Faivre-Chauvet, Thomas Carlier, Ludovic Ferrer, Pierre Baumgartner, David M Goldenberg, Robert M Sharkey, Jacques Barbet, Francoise Kraeber-Bodere, Caroline Rousseau. Pretargeted immuno-PET with an anti-carcinoembryonic antigen (CEA) bispecific antibody (BsMAb) and a 68 Ga-labeled hapten-peptide compared to conventional imaging and FDG-PET in metastatic breast cancer patients (BC): First results [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P5-01-01.