Abstract: Background and purpose: ¹⁸ F-prostate-specific membrane antigen (PSMA)-1007 positron emission tomography and computed tomography (PET/CT) is an advanced molecular imaging evaluation method for prostate cancer (PCa). This study aimed to explore the early detection rate of recurrence and metastasis of patients with biochemical recurrence (BCR) after radical prostatectomy (RP) by  ¹⁸ F-PSMA-1007 PET/CT and its influence on clinical treatment decisions. Methods: From December 2018 to December 2020, the data of 51 PCa patients with BCR after RP by  ¹⁸ F-PSMA-1007 PET/CT were summarized and analyzed. Radioactive uptake of tumors was calculated semi-quantitatively by region of interest method and expressed by the maximum standardized uptake value (SUV _max ). We assessed the detection rate of clinical recurrence and metastasis in BCR patients [local recurrence (prostatic bed), lymph node metastasis (pelvic, retroperitoneal and diaphragmatic), bone metastasis and visceral metastasis (such as lung)], and the difference in detection rate between prostate-specific antigen (PSA) groups and Gleason evaluation group was further compared respectively. Results: The median age of 51 patients was 66 years (52-80 years), and the median PSA was 35 ng/mL (6-224 ng/mL) at the time of initial diagnosis. All of them were prostatic acinar adenocarcinoma, including 1 case with intraductal carcinoma, 1 case with ductal adenocarcinoma, 1 case with mucinous adenocarcinoma, 1 case with signet ring-like component and 1 case with neuroendocrine differentiation. We found Gleason score ≤7 in 22 cases (43.14%) and Gleason score ≥ 8 in 29 cases (56.86%). The median time of BCR was 15 months (5-62 months), and the median PSA was 0.58 ng/mL (0.20- 110.00 ng/mL), including 21 (41.18%) cases with 0.20 ng/mL≤PSA ＜ 0.50 ng/mL, 12 (23.53%) cases with 0.50 ng/mL≤PSA ＜ 1.00 ng/mL, 4 (7.84%) cases with 1.00 ng/mL≤PSA ＜ 2.00 ng/mL and 14 (27.45%) cases with PSA≥2.00 ng/mL. There were 7 cases (13.73%) with no local recurrence or metastasis, and 44 cases (86.27%) with local recurrence or metastasis, including 9 cases (20.45%) with recurrence in the operative area of prostate, 28 cases (63.64%) had lymph node metastasis at different sites, 31 cases (70.45%) had bone metastasis, and 2 cases (4.55%) had visceral metastasis. In addition, there were 2 cases of subcutaneous nodule metastasis and 1 case of penile root metastasis. The median SUV _max was 17.9 (1.4-110.9) for all recurrence or metastasis, 14.0 (3.2-110.9) for local recurrence, 10.2 (2.0-90.1) for lymph node metastasis, and 5.4 (1.4-109.6) for bone metastasis. The detection rates of recurrence or metastasis were 71.43% (15/21), 100.00% (12/12), 75.00% (3/4) and 100.00% (14/14), respectively, in the groups with 0.20 ng/mL≤PSA ＜ 0.50 ng/mL (21 cases), 0.50 ng/mL≤PSA ＜ 1.00 ng/mL (12 cases), 1.00 ng/mL≤PSA ＜ 2.00 ng/mL (4 cases) and PSA≥2.00 ng/mL (14 cases), and there was no statistically significant difference in the detection rate between groups with different PSA levels (P＞0.05). The recurrence or metastasis detection rates of original Gleason score ≤7 group (22 cases) and Gleason score ≥8 group (29 cases) were 68.18% (15/22) and 100.00% (29/29), respectively, and there were statistically significant differences in the detection rate between groups with different Gleason scores (P ＜ 0.05). In clinical treatment, 4 cases (7.84%) were treated by observation, 18 cases (35.29%) by endocrinotherapy alone, 2 cases (3.92%) by salvage radiotherapy (SRT) alone, 24 cases (47.06%) by endocrinotherapy combined with SRT, 1 case (1.96%) by endocrinotherapy combined with docetaxel systemic chemotherapy, and 2 cases (3.92%) by salvage pelvic lymphadenectomy. Conclusion:  ¹⁸ F-PSMA-1007 PET/CT has a good value and efficacy in early diagnosis of clinical recurrence or metastasis of BCR patients after RP, which is conducive to accurate evaluation and optimal treatment plan for such patients, and significantly affects clinical treatment decisions.

Key words: Prostate-specific membrane antigen, Positron emission tomography and computed tomography, Biochemical recurrence, Diagnosis, Treatment