Objective:To compare the diagnostic efficacy of 68Ga-PSMA-11 PET/ CT and multi-parameter magnetic resonance imaging (mpMRI) for pelvic lymph node metastases in prostate cancer patients who received neoadjuvant endocrinology or not after initial diagnosis. Methods:Data of 52 patients with moderate and high-risk prostate cancer admitted to Xijing Hospital from February to October 2023, aged (65.8±6.6) years, preoperative prostate-specific antigen (PSA) 26.67 (13.09, 84.89) ng/ml, were retrospectively analyzed. Before operation, there were 28 cases of cT 2stage, 16 cases of cT 3 stage and 8 cases of cT 4 stage. There were 22 cases of cN 0 and 30 cases of cN 1. All patients underwent 68Ga-PSMA-11 PET/CT and mpMRI at the same time, and were diagnosed positive lymph nodes in 28 and 21 cases, respectively. Risk stratification were high risk in 45 cases, and medium risk in 7 cases. According to the preoperative endocrine treatment, they were divided into the newly diagnosed group without treatment (24 cases) and the endocrine treated group (28 cases), whose ages were (65.0±7.1) years and (66.8±6.1) years, respectively. Preoperative PSA was 26.17 (16.73, 61.18) ng/ml and 27.32 (11.94, 130.18) ng/ml, respectively. Gleason scores ≤7 were in 10 cases (41.7%) and 6 cases (21.4%), and Gleason scores >7 were in 14 cases (58.3%) and 22 cases (78.6%), respectively. There were 15 (62.5%) and 13 (46.4%) cases of cT 1-2 stage, and 9 (37.5%) and 15 (53.6%) cases of cT 3-4 stage, respectively. There were 16 (66.7%) and 6 (21.4%) cases of stage N 0, 8 (33.3%) and 22 (78.6%) cases of stage N 1, respectively. There were 22 (91.7%) and 20 (71.4%) cases of stage M 0, 2 (8.3%) and 8 (28.6%) cases of stage M 1, respectively. PET/CT diagnosis of lymph node positive was in 9 cases (37.5%) and 19 cases (67.9%), and mpMRI diagnosis of lymph node positive was in 5 cases (20.8%) and 16 cases (57.1%). The number of positive lymph nodes diagnosed by PET/CT was 13 (72.2%) and 47 (90.1%), and the number of positive lymph nodes diagnosed by mpMRI was 8 (44.4%) and 32 (61.5%). There was no significant difference ( P>0.05). All patients underwent radical prostatectomy as well as enlarged pelvic lymph node resection. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the two imaging examinations in the diagnosis of lymph node metastasis were compared according to the results of postoperative pathological examination of lymph nodes. Receiver operating characteristic (ROC) curve was used to compare the accuracy of the two imaging tests in the diagnosis of pelvic lymph node metastasis in the newly diagnosed untreated group and the endocrine treated group. Results:In this study, of 52 cases, 26 (50.0%) had positive lymph nodes by pathological examination. In this study, a total of 681 lymph nodes were dissected, with 70 lymph nodes (10.28%) being pathologically positive, and the positive rate of 26 patients was 17.99% (70/389). The PET/CT and mpMRI detection rates of 26 node-positive patients were 92.3% (24/26) and 57.7% (15/26), respectively. There were 9 (37.5%) and 17 (60.7%) lymph node positive patients in the untreated group and the endocrine therapy group, respectively. There were 320 and 361 lymph nodes were clear, with 18 (5.6%) and 52 (14.4%) positive lymph nodes, respectively. The detection rates of PET/CT and mpMRI were 88.89% (8/9) and 94.12% (16/17)in the untreated group, and 44.44% (4/9) and 64.71% (11/17)in the endocrine treated group, respectively. In the newly treated group, the area under the curve (AUC) of PET/CT and mpMRI for diagnosing positive lymph nodes were 0.911 and 0.689 ( P=0.027), the sensitivity were 88.9% and 44.4%, and the specificity were 93.3% and 93.3%, respectively. PPV were 88.9% and 80.0%, and NPV were 93.3% and 73.7%, respectively. In the endocrine therapy group, the AUC of PET/CT and mpMRI for lymph node positive diagnosis were 0.834 and 0.596 ( P=0.011), the sensitivity were 94.1% and 64.7%, the specificity were 72.7% and 54.5%, and the PPV were 84.2% and 68.8%, respectively. NPV were 88.9% and 50.0%, respectively. Conclusions:For prostate cancer patients, regardless of whether they receive neoadjuvant endocrine therapy, 68Ga-PSMA-11 PET/CT can accurately detect pelvic lymph node metastasis, and the diagnostic efficacy is significantly better than that of mpMRI.