INTRODUCTION Patients with non-metastatic prostate cancer are classified into low-, intermediate-, and high-risk groups based on baseline PSA (prostate-specific antigen) levels, Gleason score, and T stage. This risk stratification system predicts recurrence after local treatment, and the biochemical recurrence rate after five years was significantly higher in the high-risk category (>50%) than low-intermediate risk category (<50%) [1, 2]. Treatment options available for localized prostate cancer are active surveillance, radical prostatectomy, and/ or radiothera- py with/without hormonal therapy. In high-risk group, local- ized treatment (radical prostatectomy/ radiotherapy) with adjuvant hormonal therapy is recommended [3]. Serum PSA is an important biomarker in the primary diagno- sis of prostate adenocarcinoma and is also helpful in the detec- tion of recurrent disease [4]. After radical prostatectomy/ra- diotherapy, patients are followed on the PSA level and recur- rence is suggested when its level is rising [5]. Serum PSA levels after radical prostatectomy should be undetectable (< 0.1 ng/mL), and levels > 0.1 ng/mL are markers of residual prostate cancer. However, after radiation therapy, PSA levels do not return to undetectable levels because there is residual normal prostate tissue [6]. Biochemical recurrence (BCR) occurs in 27–53% of patients after definitive local therapy [7]. It is defined as post-prostatectomy PSA level ≥ 0.4 ng/ml or an increase in PSA level >2 ng/ml higher than nadir value after radiotherapy [8, 9]. The sensitivity of rising PSA levels in detecting recurrence is high but it is not informative for the localization of recurrent sites which may both be local or distant and affect the management [10]. PET/CT (choline/PSMA-based) helps to identify metastases missed by routine imaging studies (CECT National Journal of Health Sciences, 2022, 7, 115-120 115 Role of 68Ga-PSMA PET/CT in Patients with Recurrent Prostate Cancer and its Comparison with Serum PSA Levels and Gleason Scores Syed Rashid-ul- Amin 1 , Abdul Hai 1 , Haider Ali *, 1 , Najeeb Niamatullah 2 , Altaf Hashmi 3 1 Department of Nuclear Medicine and Molecular Imaging, Sindh Institute of Urology and Transplantation (SIUT), Karachi, Pakistan. 2 Department of Oncology, Sindh Institute of Urology and Transplantation (SIUT), Karachi, Pakistan. 3 Department of Urology, Sindh Institute of Urology and Transplantation (SIUT), Karachi, Pakistan. *Address correspondence to this author at the Department of Nuclear Medicine and Molecular Imaging, Sindh Institute of Urology and Transplantation (SIUT), Karachi, Pakistan. Email: doctorhaiderali@gmail.com © 2022 NIBD Publications doi.org/10.21089/njhs.73.0115 www.njhsciences.com Research Article Abstract: Background: Biochemical recurrence is seen in 27–53% of carcinoma prostate patients after treatment. GS (Gleason score) and baseline PSA level are a predictor of recurrence. Post- treatment persistent rising PSA levels represent the recurrence and PSMA labelled PET-CT is an important part of imaging workup in these patients. Objective: To detect the relationship between PSA levels and Gleason score in patients investigated for Gallium-PSMA-11 fused molecular imaging in biochemical recurrent carcinoma prostate. Material and Methods: This cross-sectional study was carried out at S.I.U.T Karachi. PSMA-PET/CT scans (September 2017-January 2022) of the patient who had a biochemical recurrence and not receiving any cancer-specific treatment at least 4 weeks prior scan were included. PSA level from lab reports and GS from the histopathological reports was recorded. Biochemical recurrence were defined as when PSA level > 0.4 ng/ml (post-prostatectomy) or >2.0 ng/ml higher than the nadir value after radiotherapy. PET/CT scans of 106 included patients were interpreted by the nuclear physician and radiologist team. SUVmax ≥ 2.5 was considered positive for recurrence. Local recurrences, lymph nodal, osseous, and visceral metastasis were documented. Statistical analysis was done by utilizing IBM SPSS software (version 22.0). Results: In 88 of 106 patients (83%), Gallium-PSMA-11 PET/CT scan detected at least one lesion characteristic of recurrent PCa. The median PSA level was 12.1 (.01-892.0) ng/dl. In relating PSA value, it was noted that there was a significant difference between lesion positive and negative PSMA-11 labelled Ga-68 PET/CT scan but not statically significant for GS. Local recurrences were seen in 70 patients, whereas lymph node and osseous metastases were noted in 64 and 52 scans respectively. A PSA value of 0.68 ng/ml was determined by utilizing the ROC curve with an AUC of 0.924 (95% CI 0.86-0.98) and will likely predict the positive/negative PSMA-11 Gallium PET/CT scan. Conclusion: Raised PSA level may predict the possibility of a positive Ga-PSMA-11 PET/CT scan but there was no relationship noted between GS and Ga-PSMA-11 PET/CT findings. Keywords: PSMA-11 labelled Gallium PET/CT scan, Biochemical recurrent carcinoma prostate, Gleason score, PSA level, Non-metastatic prostate cancer, Metastases.