An analysis of the diagnostic performance of Tc-99m PSMA SSPECT/CT in biochemically recurrent prostate cancer compared with Ga-68 PSMA PET/CT: A single-center, prospective study

Biochemical recurrence (BCR) after initial management of Prostate Carcinoma (PC) is frequent. Subsequent interventions rely on disease burden and metastasis distribution. ⁶⁸Ga prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) is an excellent imaging modality in BCR. The prospective study included 25 patients with BCR and at least one lesion on a ⁶⁸Ga-PSMA PET/CT. All patients underwent ^{99 m} Tc-PSMA SPECT/CT, and disease distribution and metastatic burden were compared with ⁶⁸Ga-PSMA PET/CT. The maximum standard uptake value (SUVmax) and the tumor-to-background ratio (TBR) were computed and analyzed. Recurrent sites were noted in the prostate (19, 76%), prostatic bed (3, 12%), and pelvis lymph nodes (LNs) (13, 52%). Distant metastasis to bones (13, 52%), lungs (5, 20%), and retroperitoneal LNs (2, 8%) were noted. Both modalities were concordant for the recurrent disease at the prostate, prostatic bed, bone, and lung lesions. ^99mTc-PSMA could localize pelvis LNs in most patients (10/13, 76.9%). No patient with systemic metastases was understaged. ^99mTc-PSMA SPECT/CT has good concordance with ⁶⁸Ga-PSMA PET/CT in BCR, even at low PSA levels. However, it may miss a few subcentimeter LNs due to lower resolution. ^99mTc-PSMA SPECT/CT could be a simple, cost-effective, and readily available imaging alternative to PET/CT