First clinical experience with a dedicated PET for hanging breast molecular imaging.

AIM: Recently, a high-resolution dedicated PET system for hanging breast imaging (MAMMI PET) has been developed to improve primary tumor detection and characterization. The aim of this pilot study was to assess its feasibility for tumor detection and FDG uptake measurements in patients with stage II and III breast cancer. METHODS: Thirty-two patients with invasive breast cancer (26 ductal, 4 lobular, 2 other), prior to and/or during neoadjuvant chemotherapy, underwent both conventional PET/CT and MAMMI PET in prone position with hanging breasts. Conventional PET/CT and MAMMI PET were performed 60±10 min and 110±10 min after injection of 180-240 MBq of FDG, respectively. Primary tumor detection was assessed and FDG uptake, expressed as maximum standardized uptake value (SUVmax), was calculated. RESULTS: Both MAMMI PET and conventional PET/CT visualized the primary tumor in 31 patients (97%). The mean distance from the tumor to the pectoral muscle was 26.4mm (smallest distance 3.3mm). Agreement in FDG uptake between PET/CT and MAMMI PET was high (r=0.86, 95% CI 0.69-0.94). However, SUVmax as assessed with MAMMI PET was consistently higher than with PET/CT in all patients with an average ratio of 2.7. CONCLUSION: The dedicated high-resolution breast PET with hanging breast technique is able to visualize approximately all breast tumors in stage II and III breast cancer patients, including tumors in the vicinity of the thoracic wall. This may enable its sequential use in the assessment of response in breast cancer patients receiving neoadjuvant systemic therapy, although SUVmax values are not directly comparable to standard PET/CT.