Objective:To investigate the value of 18F-PSMA PET/CT-derived prostate specific membrane antigen(PSMA)expression parameters, including maximum standardize uptake value(SUV max), PSMA receptor expressing tumor volume(PSMA-TV), and total lesion PSMA receptor expression(TL-PSMA), in predicting the risk of metastasis in elderly prostate cancer patients aged 60 years and older. Methods:Clinical data of 39 patients with prostate cancer diagnosed in our hospital from January 2019 to May 2021 and imaging data of 18F-PSMA PET/CT before treatment were analyzed retrospectively.PSMA-TV and TL-PSMA of primary tumor tissue were calculated from PET/CT images with 40% of the SUV max as the threshold value.The influence of 18F-PSMA PET/CT on clinical TNM staging was evaluated.The Mann-Whitney U test was used to compare the differences in values of various indicators between the groups with or without metastasis, including the total prostate-specific antigen(tPSA)level, Gleason score and PSMA expression parameters.The correlation of PSMA expression parameters with tPSA and Gleason score was analyzed.The area under the receiver operating characteristic(ROC)curve(AUC)was used to determine the predictive ability of different indicators for the risk of prostate cancer metastasis, and multivariate logistic regression analysis was used to screen for independent predictors of prostate cancer metastasis. Results:The Gleason score of 39 prostate cancer patients(median age: 67 years, age range: 60-83 years)was 7.0(7.0, 8.0), and the median prostate specific antigen(PSA)level was 14.83(7.37, 30.93)μg/L.There were 11 cases(28.2%)with metastasis(the metastasis group), and 28 cases(71.8%)without metastasis(the non-metastasis group). Based on PET/CT, the clinical N and M stages of five patients(12.8%)were changed, but two cases(5.1%)with pelvic lymph node metastasis were missed.The median ages of the metastasis group and the non-metastasis group were 63(60-79)years and 69(60-83)years, respectively, and the difference was not statistically significant( P=0.115). The metastasis group and the non-metastasis group had tPSA levels at 54.0(9.9, 75.8)μg/L and 10.2(6.8, 22.8)μg/L, the SUV max at 29.1(16.8, 35.3)and 7.7(6.0, 13.6), the PSMA-TV at 41.5(22.4, 90.9)cm 3 and 6.8(3.6, 9.3)cm 3, TL-PSMA at 279(139.7, 996.4)and 25.5(15.9, 37.0), Gleason scores at 8.0(7.0, 8.0)and 7.0(7.0, 8.0), respectively.There were statistically significant differences in tPSA( Z=-2.528, P=0.011), SUV max( Z=-4.151, P<0.001), PSMA-TV( Z=-3.995, P<0.001)and TL-PSMA( Z=-4.213, P<0.001)between the two groups.SUV max( r=0.537, P<0.01), PSMA-TV( r=0.496, P<0.01)and TL-PSMA( r=0.508, P<0.01)were all positively correlated with tPSA.Furthermore, SUV max( r=0.547, P<0.01), PSMA-TV( r=0.412, P<0.01)and TL-PSMA( r=0.433, P<0.01)were also positively correlated with Gleason score.ROC curve analysis showed that the AUCs of SUV max, PSMA-TV, TL-PSMA and tPSA in predicting prostate cancer metastasis were 0.932, 0.916, 0.938 and 0.763, respectively.Multivariate Logistic regression analysis showed that SUV max( OR=1.203, 95% CI: 1.001-1.445, P=0.049)was an independent predictor of prostate cancer metastasis. Conclusions:These PSMA expression parameters of 18F-PSMA PET/CT have a good value in predicting the risk of metastasis in elderly prostate cancer patients, and SUV maxmay serve as a potential molecular imaging indicator to independently predict prostate cancer metastasis.