Transrectal ultrasound-guided TRBx is the main method to diagnose prostate cancer without surgery [6,7]. However, false negative rate (FNR) is higher in transrectal puncture, which is reported to be up to 15%~31% [8,9,10]. It was reported that TPBx could significantly improve the detection rate of tumors in the anterior half and apex of the prostate compared with TRBx [11,12,13], and can accurately assess the PV, at the same time,it has the advantage of safety and low infection rate, transperineal biopsy is becoming more and more popular in prostate biopsy [6, 14]. However, better selection of prostate biopsy indications, improvement of the positive rate of puncture of the prostate are still hot issues .
The positive rate of TPBx in this study was 35.8%, slightly higher than the rate (34.5%) reported by Pepe P et al , but generally lower than that reported by foreign literatures [16, 17]. This difference may be mainly caused by racial difference, because the incidence of Pca in European and American is much higher than that in China, and the differences caused by such factors as inconsistent pathological diagnostic criteria cannot be excluded.
The cut-off points for age, t-PSA, f-PSA, PSAD, f/t PSA and PV were 73 years old, 15.43 ng/ml, 4.545 ng/ml, 0.475 ng/ml*cm3, 0.123 and 41.45 ml, respectively. Compared with the current puncture guidelines , t-PSA and PSAD are higher, while f/t PSA is lower, which may be related to the fact that the enrolled patients have been screened by the guidelines. Compared with the Pca patients in the United States reported in the literature [18,19], the results of this study showed that Pca in Chinese had the characteristics of older age, higher t-PSA and smaller PV. In terms of clinical manifestations, this study found that the positive rate of TPBx in symptomless patients was higher, and lower in patients with prostatitis, dysuria and hematuria. This may be related to the fact that most of the patients received TPBx only because of abnormal prostate screening, and most of the patients’ dysuria and hematuria and other symptoms may be caused by diseases such as benign prostatic hyperplasia.
Compared with TRBx, TPBx significantly increased the tissue acquisition of TZ in the prostate, and also increased the tissue acquisition of PZ to a certain extent. However, TPBx is prone to omission in the detection of basal tumors. Although the incidence of prostate cancer is not high in the basal region [20,21], the puncture of the basal region should be paid more attention in TPBx, especially for patients with imaging space occupying near the basal region. As it is reported that in the PZ, especially in the apex of prostate, is the most common site of Pca. Breslow et al.  analyzed the results of 1327 autopsies in seven centers around the world and found 350 cases of latent Pca, which mainly appeared in the PZ, most of which were 5 ~ 15 mm from the apex of prostate, and the tumor incidence was the same in the anterior and posterior regions. The results of 271 Pca patients in this study suggested that the PRPN of PZ was higher than that of TZ, which was consistent with the literature. However, further comparison revealed that the PRPN of LZ was higher, especially the PRPN of LPZ was significantly higher than that of the rest; When CFVR was compared, it was found that the CFVR of LTZ was significantly larger than that of the other regions; When comparing PRCF, we found that the PRCF of LPZ and LTZ were significantly higher than that of RPZ or RTZ, and there was no significant statistical difference between LPZ and LTZ, RPZ and RTZ. This result may be caused by the existence of a large number of small cancer foci in the LPZ, a small number of large cancer foci in the LTZ, and a small number of small cancer foci in the RPZ and the RTZ. We draw the conclusion that: Increasing the puncture in the LPZ may improve the detection rate of Pca. Increasing the puncture in the LTZ may allow more accurate staging of patients to guide subsequent treatment. Although the positive rate of RZ puncture is lower than that of LZ, the puncture in the RZ should not be neglected.
Gleason scoring system has become the standard pathological grading system for Pca in WHO since 1993 , it has become the most important indicator for evaluating the invasion of tumors and determining the prognosis of patients , and the accuracy of predicting the progression of localized Pca is 30%~69% . As it was reported in the study results of the largest international prostate puncture collaboration group that the proportion of high-level Pca (Gleason score 7 ~ 10) in clinical cohort in European and American countries is 30% and 51% respectively. In our study, the proportion was 62%, significantly higher than that reported in the literature. This may be related to racial difference, or it may be caused by different pathological evaluation criteria (the new grading system of 2015 version  was adopted in our study). When cancer lesions were further divided into different Gleason scores. There was no difference in CFVR and PRCF between different areas (Gleason score 6–7). The PRPN of LPZ was higher than that of other regions, and the CFVR of LTZ was significantly higher than that of other regions (Gleason score 8–10). This result further indicates that the high PRCF of LZ may be related to the high Gleason score of Pca lesions in the LZ. We compared the biopsy pathology and postoperative pathology of 120 patients with RP after puncture, and found that the Gleason score of postoperative pathological was 0.275 points higher than that of puncture pathology, which may be related to the fact that more tissues can be obtained from RP for more accurate pathological assessment.
Limitations: ①.This paper is a retrospective study with a small sample size and possible bias in data. Therefore, it is necessary to further expand the sample size. ②. It was a single-center study and lacked a contrast in the study of the spatial distribution of Pca by TRBx. ③.Digital rectal examination was not included in the multivariate analysis. ④. The clinical features such as risk factors, diagnostic efficacy and critical values of t-PSA in gray area (4 ~ 10 ng/ml, 2016 consensus of Chinese experts on prostate puncture ) were not analyzed. ⑤. Patients in our study group have been screened by puncture guidelines, and the cut-off point of t-PSA obtained may be relatively high, the obtained critical value of f/t PSA and PSAD is only the diagnostic critical value of all enrolled patients, which is not equal to the critical value of gray area. ⑥. Postoperative pathology of RP patients was recorded only by the highest Gleason score, and the distribution of cancer lesions was not recorded in different regions and analyzed.