Feasibility of 99m Tc-MIP-1404 for SPECT/CT imaging and subsequent PSMA-radioguided surgery in early biochemical recurrent prostate cancer: a case series of 9 patients

This case series evaluated the feasibility of prostate-specific membrane antigen (PSMA) radioguided surgery (RGS) with 99mTc-MIP-1404 in recurrent prostate cancer. Methods: 9 patients with PSMA-positive lesions on PET/CT received 99mTc-MIP-1404 (median 747 MBq, interquartile range (IQR) 710 - 764) 17.2 hours (IQR 16.9 - 17.5) before SPECT/CT and 22.3 hours (IQR 20.8 - 24.0) before RGS. Results: 17 PSMA-positive lesions were detected on PET/CT (median short axis diameter 4 mm, IQR 3 - 6; median SUVmax 8.9, IQR 5.2 - 12.6). 9/17 (52.9%) were visible on SPECT/CT (median SUVmax 13.8, IQR 8.0 - 17.9). Except for 2 foci, all PET/CT-positive findings demonstrated intraoperative count rates above the background (median counts 31, IQR 17 - 89) and were lymph node metastases. Moreover, PSMA-RGS identified 2 additional metastases compared to PET/CT. Prostate-specific antigen values decreased after RGS in 6/9 (67%) patients. Conclusion: PSMA-RGS with 99mTc-MIP-1404 identified lymph node metastases in all patients including two additional lesions compared to PET/CT.