Presentation Authors: Muhammad Junaid Niaz*, Yuliya Jhanwar, Thomas Flynn, Shankar Vallabhajosula, Jaspreet Batra, Scott Tagawa, Francesca Khani, Brian Robinson, Neil Bander, Douglas Scherr, New York, NY
Introduction: Due to the high expression of Prostate Specific Membrane Antigen (PSMA), it is an excellent target for molecular imaging. IAB2M is an 85kD minibody derived from J591 and PSMA-11 is a PSMA small molecule ligand.
Methods: Patients with clinically significant (defined as â‰¥ 0.5 cm3 with Gleason pattern â‰¥ 4) localized prostate cancer(PCa) on conventional imaging modalities who planned to undergo surgery were imaged by PET/CT 90 -120 minutes after 5Â±2mCi of 68Ga-PSMA-11 injection and 2-4 days after 10mg IAB2M labeled with 2.5 mCi of 89Zr injection. Image results were read and mapped by a Nuclear Medicine MD without knowledge of the surgical pathology. Mapped findings were later compared with a surgical pathology map.
Results: 20 patients with median age 64.5(46-79) and PSA 7.5(1.6-36.56) were enrolled. The first 11 patients were imaged only by IAB2M while last 9 patients were imaged by both IAB2M and PSMA-11. IAB2M detected 18 of 19 (95%) dominant lesions which had a median Gleason score 7.5(6-9) in 19 patients; PSMA-11 detected 100% of dominant lesions with median Gleason score 8(6-9) in 8 patients. One patient refused surgery. The smallest dominant lesion detected was 8mm in size. The one dominant lesion missed by IAB2M was 7mm. Median SUVmax for dominant lesions was 3.1(1.0-7.5) on IAB2M and 7.1(1.6-23.2) on PSMA-11; median MR PIRADS was 4(4-5). Of 17 Gleason 6 lesions identified on pathology, IAB2M detected 7 (41%) and of 9 lesions on pathology, PSMA-11 detected 3 (33%). Extraprostatic lesions: in the first 11 patients who got only IAB2M, 3 patients had 7 extra-prostatic lesions; 4 extra-prostatic lesions were detected and confirmed by surgical path and 3 lesions were missed. In the subsequent 9 patients who got both PET scans, 4 extra-prostatic lesions in one patient were detected by both PET agents, 3 were confirmed by surgical pathology and 1 confirmed on bone scan 2 months post-op. 15 false positive lesions were detected by IAB2M in 20 patients and 5 false positives were detected by PSMA-11 in the last 9 patients. There were 11 false negative lesions on IAB2M in all 19 patients and 3 false negatives on PSMA-11 in 8 patients. Of these false negatives, 7 were GS 6 and 2 were 3+4 and LNs median size was 2mm (0.5-15).
Conclusions: In this small series, the performance of both PET agents was very similar. An advantage of IAB2M is its hepatobiliary rather than renal/urinary clearance, which makes it potentially easier to visualize the PCa and/or pelvic disease; an advantage of PSMA-11 is the ability to image within 1-2 hours.
Source of Funding: Department of Urology, Weill Cornell Medical College, New York