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Table of Contents
ORIGINAL ARTICLE
Year : 2020  |  Volume : 31  |  Issue : 4  |  Page : 163-169

The value of prostate-specific antigen-age volume score in predicting prostate cancer in Taiwan


1 Department of Urology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
2 Department of Urology, Kaohsiung Medical University Hospital; Department of Urology, Kaohsiung Municipal Siaogang Hospital, Kaohsiung, Taiwan
3 Department of Urology, Kaohsiung Medical University Hospital, Kaohsiung; Department of Urology, Ministry of Health and Welfare Pingtung Hospital, Pingtung; Department of Urology, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
4 Department of Urology, Kaohsiung Medical University Hospital; Department of Urology, School of Medicine, College of Medicine, Kaohsiung Medical University; Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan
5 Department of Urology, Kaohsiung Medical University Hospital; Department of Urology, Kaohsiung Municipal Siaogang Hospital; Department of Urology, School of Medicine, College of Medicine, Kaohsiung Medical University; Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan

Date of Submission21-Nov-2019
Date of Decision20-Jan-2020
Date of Acceptance23-Jan-2020
Date of Web Publication25-Jul-2020

Correspondence Address:
Jhen-Hao Jhan
Department of Urology, School of Medicine, College of Medicine, Kaohsiung Medical University, No. 100, Shiquan 1st Rd., Sanmin Dist., Kaohsiung City 807
Taiwan
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/UROS.UROS_89_19

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  Abstract 


Purpose: Whether the predictive utility of prostate-specific antigen-age volume (PSA-AV) score can surpass serum total PSA, age-adjusted PSA, or PSA density (PSAD) has remained unclear based on previous reports. The aims of this study were to assess the predictive value of PSA-AV score in a Taiwanese population. Materials and Methods: We retrospectively reviewed the medical data of patients who underwent transrectal ultrasound-guided prostate biopsy between 2007 and 2013 at our institution. The ability of serum PSA, age-adjusted PSA, PSAD, and PSA-AV to predict prostate cancer was tested using receiver operating characteristic (ROC) curves. Results: A total of 415 biopsy specimens were included in the study, of which 75 (18.1%) were diagnosed with prostate cancer. The discriminative performance of serum PSA, age-adjusted PSA, PSAD, and PSA-AV for predicting prostate cancer was evaluated in the study cohort. The areas under ROC curve were determined for the four tests as follows: for serum PSA (95% confidence interval [CI]: 0.723–0.852), for age-adjusted PSA (95% CI: 0.719–0.888), for PSAD (95% CI: 0.673–0.877), and for the formula PSA-AV (95% CI: 0.783–0.884), they were 0.787, 0.804, 0.775, and 0.834, respectively. Comparing other tests, the novel formula PSA-AV was significantly better than the other three PSA-derived tests and reached statistical significance (P < 0.05). At this cutoff value (PSA-AV <200), the sensitivity was 74.7% and the specificity was 77.4%. Conclusion: The use of the formula PSA-AV in Taiwan was superior in the prediction of prostate biopsy findings compared to serum PSA, age-adjusted PSA, and PSAD according to our data, particularly in older patients or patients with a larger prostate volume.

Keywords: Age-adjusted prostate-specific antigen, prostate cancer, prostate-specific antigen density, prostate-specific antigen-age volume, transrectal ultrasound-guided prostate biopsy


How to cite this article:
Lin CH, Chang CW, Li WM, Wen SC, Huang SP, Li CC, Wu WJ, Ke HL, Lee YC, Jhan JH. The value of prostate-specific antigen-age volume score in predicting prostate cancer in Taiwan. Urol Sci 2020;31:163-9

How to cite this URL:
Lin CH, Chang CW, Li WM, Wen SC, Huang SP, Li CC, Wu WJ, Ke HL, Lee YC, Jhan JH. The value of prostate-specific antigen-age volume score in predicting prostate cancer in Taiwan. Urol Sci [serial online] 2020 [cited 2020 Aug 10];31:163-9. Available from: http://www.e-urol-sci.com/text.asp?2020/31/4/163/290861




  Introduction Top


It is known that prostate cancer is one of the most common malignancies worldwide and the second leading cause of cancer-related mortality in men.[1] The screening and detection of clinically significant prostate cancer have become an important medical issue. Regarding screening and detecting prostate cancer, digital rectal examinations (DREs) and serum prostate-specific antigen (PSA) evaluations are generally recommended.[2] Although much effort has been made to create more sensitive and specific formulas such as PSA density (PSAD), free/total PSA ratio, and PSA velocity, serum total PSA is still the most widely used biomarker in day-to-day practice for screening prostate cancer. However, serum PSA is an organ-specific rather than disease-specific biomarker, so the wide utilization of serum PSA in prostate cancer screening has demonstrated low specificity at its usual cutoff (e.g., 4.0 ng/ml) and led to false-positive results, making the decision regarding biopsy challenging, especially in the “gray-zone” (PSA 4–10 ng/ml).[2],[3]

In the United States, almost 1 million prostate biopsies are performed annually to confirm or rule out prostate cancer,[4] despite the fact that many patients are subjected to an unnecessary prostate biopsy that is an invasive procedure and might lead to severe complications and even mortalities.[5],[6] Therefore, a better predictor to improve the detection of clinically significant prostate cancer and to avoid unnecessary biopsies without compromising the overall cancer detection rate is of crucial concern. Since its introduction more than two decades ago, the clinical variables of age-specific PSA and PSAD have been shown to be associated with better performance in detecting prostate cancer worldwide.[7],[8],[9],[10] Patel et al. further developed a novel algorithm that incorporates these parameters into a single formula for predicting positive prostate biopsy results, called PSA-age volume (PSA-AV) score.[11] By multiplying prostate volume and patient's age and then dividing the total by serum PSA, the PSA-AV score can be easily calculated. Patel et al. found that a cutoff value of 700 was more specific in older patients and in patients with a large prostate volume. Later, in one study, the predictive effect for a PSA-AV score of 700 was similar to a serum PSA cutoff of 4.0 ng/ml,[12] and another study showed that PSA-AV score performed equally well as PSAD and was better than serum PSA.[13]

The PSA-AV formula has been put forward as a possibly better predictor in detecting prostate cancer, yet the optimal cutoff points remain controversial especially in Asian countries. Besides, whether the predictive utility of PSA-AV could surpass serum PSA, age-adjusted PSA, or PSAD is still unclear based on previous reports. In addition, the clinical features of the Taiwanese biopsy population differ from that of Africans and Caucasians (generally with elder age and higher serum PSA level).[14],[15],[16] As this issue has never been addressed in Taiwan, we present a retrospective study evaluating the novel score for the detection of positive prostate biopsy findings by reviewing our medical data. This is the first study comparing the overall predictive values of serum PSA, age-adjusted PSA, PSAD, and PSA-AV in a Taiwanese population. The aim of this study is to examine whether the predictive value of PSA-AV can surpass that of serum total PSA, age-adjusted PSA, or PSAD and to also find an optimal cutoff level to improve cancer detection rate and avoid unnecessary biopsies.


  Materials and Methods Top


Study population and sample collection

This retrospective study was approved by the Institutional Review Board of Kaohsiung Medical University Hospital (KMUHIRB-E(I)-20180089). We enrolled 436 men who underwent transrectal ultrasound (TRUS)-guided prostate biopsy at our institute between August 2007 and October 2013. The indications for TRUS-guide biopsy at our institute were as follows: (1) elevated serum PSA level (defined as >4.0 ng/mL) and (2) abnormal findings on a DRE with any level of PSA. The patients' baseline characteristics including age, family history, body mass index, renal function, prebiopsy serum PSA level, measured prostate volume, and DRE findings were recorded. Data were obtained by retrospectively reviewing the medical charts and examining the pathohistological results as well as complications following prostate biopsies. The informed consent was waived by IRB.

All TRUS-guided biopsies were performed using a B&K machine (Flex Focus 800 by B&K medical system as TRUS-biopsy machine) by an experienced urologist. We used a 10–12-core extended-sampling systemic biopsy protocol for the peripheral zone under ultrasound guidance. Each core was sampled separately, stored in formaldehyde, and then sent for pathological assessment. A biopsy was defined as positive only when adenocarcinoma was observed in the final histological evaluation. In positive samples, the Gleason score, number of positive cores, and maximum percent infiltrated were recorded.

Statistical analysis

A total of 436 biopsy records were reviewed. Patients with incomplete demographic data, those lost to follow-up, or those who had undergone repeat biopsies were excluded from the study. A total of 415 biopsy specimens were analyzed.

The PSAD was calculated as prebiopsy total PSA (ng/ml) divided by prostate volume (ml). As regards age-adjusted PSA, we defined the abnormal values in different age categories as follows: >6.5 ng/mL (age >70 years), >4.5 ng/mL (age 60–69 years), and >3.5 ng/mL (age <60 years). The PSA-AV score was calculated by multiplying the age and prostate volume and then dividing the total by the prebiopsy serum PSA level. Multiple statistical analyses were performed to determine a score that included the most significant factors predicting the diagnosis of prostate cancer. Analyses were conducted using SPSS version 19.0 (SPSS Inc., Chicago, IL, USA), and differences were deemed statistically significant if P < 0.05.

The ability of serum PSA, age-adjusted PSA, PSAD, and PSA-AV to predict prostate cancer was tested using receiver operating characteristic (ROC) curves. The overall performance of the ROC analysis was quantified by computing the area under the curve (AUC). An area of 1 indicated perfect performance, while 0.5 indicated a performance that was not different than chance. Patel et al. stratified the PSA-AV score in intervals of 400,[11] but we stratified in intervals of 100 to determine an effective cutoff score for predicting prostate cancer in a meticulous way. The sensitivities and specificities of various PSA-AV cutoffs were analyzed to better compare them with the age-adjusted PSA levels and serum PSA cutoff of 4 ng/mL. The database was also stratified in different age groups and different prostate volume groups to easily compare positive predictive value (PPV) and sensitivity and specificity values.


  Results Top


A total of 415 patients were enrolled in this study, of whom 75 (18.1%) patients were diagnosed with prostate cancer. The average age of the population in our study was 67.9 ± 9 (n = 415). The mean total serum PSA level and prostate volume were 28.2 ± 95.8 ng/mL (10% trimmed mean) and 50.8 ± 25 cm 3 (10% trimmed mean), respectively.

[Table 1] shows the baseline characteristics of our study cohort. The discriminative performance of serum PSA, age-adjusted PSA, PSAD, and PSA-AV for predicting malignancy was evaluated in the study cohort [Table 2]. The AUCs were determined for the four tests as follows: for PSA, 0.787 (95% confidence interval [CI]: 0.723–0.852); for age-adjusted PSA, 0.804 (95% CI: 0.719–0.888); for PSAD, 0.775 (95% CI: 0.673–0.877); and for PSA-AV, 0.834 (95% CI: 0.783–0.884). Comparing these four tests, the novel formula PSA-AV was significantly better than the other three PSA-derived tests and reached statistical significance (P < 0.05). [Figure 1] shows the ROC curves which revealed that PSA-AV outperformed serum PSA, age-adjusted PSA, and PSAD in our study cohort (P < 0.05).
Table 1: Characteristics of the study cohort

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Table 2: Evaluation of area under the receiver operating curves of prostate-specific antigen and its derivatives

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Figure 1: Receiver operating characteristics of prostate-specific antigen-age volume, prostate-specific antigen, and age-adjusted prostate-specific antigen (a) predicting the result of prostate cancer in the entire population using prostate-specific antigen-age volume, (b) predicting the result of prostate cancer in the entire population using prostate-specific antigen, and (c) predicting the result of prostate cancer in the entire population using age-adjusted prostate-specific antigen

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We further calculated the sensitivity and specificity of serum PSA, age-adjusted PSA, PSAD, and PSA-AV at different cutoff scores. As shown in [Figure 2], when the PSA-AV cutoff score increased from 200 to 800, the sensitivity increased from 74.7% to 98.7% and the specificity decreased from 77.4% to 4.1%. We calculated Youden's indexes of different PSA-AV cutoffs to determine the best cutoff value. Youden's index values (sensitivity + specificity −1) are larger when both sensitivity and specificity are higher, which indicates that the best cutoff has been identified. Overall in our study cohort, we found that the cutoff of <213 performed best among these, and the sensitivity and specificity were 74.7% and 77.4%, respectively.
Figure 2: Sensitivity and specificity at various prostate-specific antigen, prostate-specific antigen-age volume, and age-adjusted prostate-specific antigen

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The sensitivity of the commonly used prostate cancer detection tests in Taiwan as serum PSA (cutoff >4 ng/mL), age-adjusted PSA method (cutoff mentioned as above), and PSAD (cutoff ≥0.15) was 85%, 76%, and 80%, respectively, while their specificity was 30%, 35%, and 43%, respectively. The PPV of the PSA-AV score of 200 was 42%, and this is greater than the PPV for the PSA ≥4 ng/mL, age-adjusted PSA, and PSAD methods (35%, 26%, and 32%, respectively). The numbers of detected and missed prostate cancers using these four tests were calculated and compared. Using the novel formula PSA-AV, cutoff of <200 led to 26 more biopsies and detection of 10 more malignancies compared to using the cutoff of serum PSA ≥4 ng/mL. In comparison with PSAD in the same population, it led to 16 fewer biopsies and 7 additional cancer cases detected. Comparing the misdetection rates of the differences of PSA-AV <200 and age-adjusted PSA also revealed that using PSA-AV <200 would have missed fewer prostate cancer patients than the age-adjusted PSA method.

Furthermore, we examined the sensitivity and specificity in the different age and various prostate volume groups. The results are listed to better determine an effective cutoff score in a meticulous way [Table 3] and [Table 4]. The best cutoff point among the different age groups (age <65, age 66–75, and age >75) was 213.83, 223.34, and 172.02, respectively. The sensitivity of different age groups was 71.7%, 78.1%, and 83.1%, respectively, while the specificity was 66.7%, 83.3%, and 79.2%, respectively. The best cutoff among various prostate volumes was 159.12, 214.09, and 292.4, respectively (PV <30 cm 3, 31–60 cm 3, and >61 cm 3). The sensitivity of various prostate volumes was 64.3%, 77.5%, and 78%, respectively, while the specificity was 72.7%, 81.4%, and 88.9%, respectively. A PSA-AV cutoff of 200 seemed to perform better for older patients (age over 75 years) and in patients with large prostate (PV >60 ml), while the differences between their AUCs reached statistical significance [Table 5] and [Table 6].
Table 3: Sensitivity and specificity of various cutoff prostatespecific antigen-age volume in different age groups

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Table 4: Sensitivity and specificity of various cutoff prostatespecific antigenage volume in different prostate volume groups

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Table 5: Evaluation of area under the receiver operating curves of prostate-specific antigen-age volume in different age groups

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Table 6: Evaluation of area under the receiver operating curves of prostate-specific antigen-age volume in different prostate volume groups

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  Discussion Top


The imperfection in the sensitivity and specificity of total serum PSA for prostate cancer detection remains problematic and might cause inappropriate biopsy at its usual cutoff (normally 4.0 ng/ml). Although widely used for screening of prostate cancer, serum PSA is not a cancer-specific marker. While age increases, the prostate gland generally also increases in size and produces more PSA. In addition to malignancy, the serum PSA level might also become elevated in some benign conditions including inflammation or hyperplasia of the prostate. Therefore, the use of PSAD as an indicator for prostate biopsy was investigated, and prostate volume was brought into consideration to decrease the influence of prostatic hyperplasia on serum PSA level.

Although using PSAD for prostate cancer detection has generated controversy, it is still recommended that PSAD be applied with a cutoff level of 0.15 to promote prostate biopsy in Taiwan guidelines in the gray zone (PSA values = 4–10 ng/ml) based on Western references. On the other hand, the age-adjusted PSA method takes into consideration native enlargement as the prostate grows in aging males at PSA values; however, it is still controversial while using age-adjusted PSA as an indication for biopsy.[17]

In order to better predict the likelihood of a positive biopsy, Patel et al. combined clinically significant predictors within a nomogram.[11] The novel PSA-AV formula incorporates prostate volume, age, and serum PSA into an uncomplicated calculating score. In their validation study, they found that a PSA-AV cutoff value of 700 was better than PSA for predicting positive biopsy. Later, in another study, the predictive effect for a PSA-AV score of 700 was similar to a PSA cutoff of 4.0 ng/ml, and another study showed that PSA-AV score performed equally well as PSAD and was better than serum PSA.[12],[13]

In the present study, our results revealed that the AUC of PSA-AV was 0.834 and performed better than other prostate biopsy indicators as serum PSA, age-adjusted PSA, and PSAD (AUCs = 0.787, 0.804, and 0.775, respectively). At the cutoff of 200, the sensitivity and specificity were 74.7% and 77.4%, respectively, both surpassing the sensitivity and specificity of a serum PSA cutoff of 4 ng/mL, age-adjusted PSA, and PSAD. Considering all of the biopsies, using the PSA-AV of 200 increased the number of biopsies by 26 and 10 more detected cancer cases compared to using serum PSA cutoff of 4 ng/mL. In comparison with PSAD in the same population, it led to 16 fewer biopsies and 7 additional cancer cases detected. These superiority results stand in comparison with earlier studies.[11],[12],[13]

In our study, the optimal PSA-AV cutoff value was lower than that reported by Patel et al. We used the Youden indexes of various PSA-AV scores (<200, <300, <400, <500, <600, and <800) to identify the best cutoff values so as to be compared with previous studies. It showed that PSA-AV <200 performed best among these, and at this cutoff value (PSA-AV <200), the sensitivity was 74.7% and the specificity was 77.4%. The reason of different optimal cutoff value in different countries or studies might be complicated and not easy to explain. As serum PSA screening and DRE are not included in the periodic comprehensive medical examination in Taiwan, the delay biopsy-and-diagnosis trend in the Taiwanese population is probably one of the reasons. Besides, the race cause should be taken into consideration, as the Taiwanese population is a multi-ethnic population, including people from mainland China, indigenous peoples, and descendants from Japan or nearby countries, and does not fit into discrete racial origins. Our results of PSA-AV cutoffs differed from those reported by Wu et al.,[13] which recommend that distinguished regions and populations need to have their own standard cutoff values. At this PSA-AV cutoff value of 200, the sensitivity was not obviously inferior compared to previous studies, and the specificity was far better than that of all former reports; consequently, we advise a PSA-AV cutoff of 200 in the Taiwanese population.

Another issue that might be of concern was the location of core biopsy. Former studies did not promote routine transitional zone sampling during first biopsy due to very few malignancies being discovered peculiarly in the transitional zone. On the contrary, far-lateral and apical region sampling might improve cancer detection rates and also reduce the need for repeat biopsies. Babaian et al. evaluated 85 patients who underwent first biopsy, and 7 cancers were identified uniquely in the anterior-horn (far lateral) and only 2 cancers were found uniquely in the transitional zone.[18] Singh et al. also demonstrated the benefit of lateral sampling. In their prostatectomy samples, the laterally directed cores are independent predictors for pathological features.[19]

In our protocol for prostate biopsy, we do not perform transitional zone biopsy nor routinely perform apical and far-lateral region sampling. This could be among the reasons why our cancer detection rate (18.1%, 75/415) was relatively low compared with that of previous studies (27%–52% with 10–12-core biopsy strategy).[18]

Moreover, our data suggested that using PSA-AV cutoff values of 200 is a better indicator for prostate biopsy in extreme age groups. In stratified groups with different age, the PPV of PSA-AV 200 had better performance compared to different cutoffs as shown in [Table 3]. In patients >75 years, the AUC was 0.879, reaching statistical significance and being greater than other age groups [Table 5]. The cutoff of 200 also functioned well in the larger prostate volume groups as it rationalized prostate volume in its formula. The presentation of PPV at a cutoff of 200 was greater than that at different cutoffs in stratified prostate volume groups [Table 4]. In patients with a prostate volume >60 cm 3, AUC was 0.845 and better among low prostate volume (<20 cm 3) and moderate prostate volume (30–60 cm 3) cases [Table 6]. Thus, in a Taiwanese population, a PSA-AV score of 200 would be an excellent tool to predict the presence of prostate cancer in older patients (>75 years) with a large prostate (>60 cm 3). As many patients with prostate cancer die of conditions other than their primary cancer, it is important to avoid unnecessary biopsies in this age group to improve the detection of prostate cancer and decrease disastrous complications. Previous studies showed that the incidence of biopsy-related infectious complications ranged from 0.1% to 7%, and roughly 30%–50% of these patients had bacteremia,[20] which is frequently accompanied by severe sepsis and may sometimes be life-threatening. Hence, the benefit of cancer detection must be weighed against the risk of unnecessary biopsies especially in older groups over 75 years often presenting with more comorbidities.

The present study has various limitations; first, it was a retrospective study from a single health institute. Nevertheless, as the institute is one of the medical centers with many branches covering a special municipality in Taiwan, there are patients from all over the country seeking medical assistance at our center. Consequently, our report population might partially represent the Taiwanese population. Besides, this study did not divide the patients according to Gleason score, and we did not evaluate insignificant prostate cancers in the study population. However, previously published work has reported no observed differences among PSA-AV, PSAD, and PSA while forecasting high-grade prostate cancer.[15] We recommend further studies should assess the relationship between PSA-AV score and prostate cancer grades.

To the best of our knowledge, this study is the first database demonstrating optimal cutoff values of PSA-AV score in Taiwan. The strengths of the present study incorporated the large local population of prostate biopsy, an appropriate PSA-AV cutoff of 200 in Taiwan, and a 12-core biopsy with apical and far-lateral region sampling considered as standard protocols.


  Conclusion Top


Our study suggests that the value of the novel formula PSA-AV is superior in the detection of prostate cancer vis-à-vis serum PSA, age-adjusted PSA, and PSAD in a Taiwanese population. Unlike former Western studies, the optimal PSA-AV cutoff is 200 in Taiwanese patients. Particularly, this could become a great tool to predict the presence of prostate cancer and avoid unnecessary biopsies in older patients or patients with a larger prostate.

Acknowledgments

The authors would like to acknowledge the Statistical Analysis Laboratory in the Department of Medical Research at Kaohsiung Medical University Hospital.

Financial support and sponsorship

The study was supported by grants from Kaohsiung Medical University Hospital (KMUH-107-7M28).

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

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