Measurement of the level of PSA in serum in the elderly can help clinicians to diagnose prostate cancer at an early stage. However, other medical conditions, such as benign prostatic hypertrophy and inflammation, can elevate the PSA level in serum [
14]. Because of the low specificity of the PSA level in the detection of prostate cancer, patients suspected of having this disease using PSA screening usually receive an unnecessary biopsy; this is an invasive procedure with accompanying complications [
15]. The benefit of PSA screening in prolonging cancer-specific survival remains controversial [
16,
17]. Previous research has shown that predictive models, based on clinical, laboratory and ultrasound parameters can improve the accuracy of prostate cancer detection to varying degrees [
18‐
20]. In the present study, Ln(PV), f/t, age, Ln(PSA), the rate of abnormal DRE findings and the rate of hypoechoic masses detected using TRUS have been taken into account for the first time. The equation used in the calculation of the PCP was derived for the diagnosis of prostate cancer. In contrast to PSA alone, use of our nomogram enlarged the AUC from 0.761 to 0.853. As shown in Figure
2B, C and D, we could evaluate the positive core rate, Gleason score and estimate the number of positive cores. In principle, a higher risk level means a higher positive rate, a higher Gleason score and more calculations regarding positive cores. As is evident in Figure
2C, the general tendency regarding the mean number of positive cores is not adequate in the first risk level; however, the difference between the first risk level and the second risk level was not significant (4.32 vs. 3.84; P = 0.473).
More recently, surgeons have used additional biopsy cores to improve the accuracy of detection of prostate cancer [
9‐
14]. However, it has been reported in some studies that there is no significant difference between 6-core biopsy and 12-core biopsy in terms of the rate of positive biopsy cores [
21,
22]. According to our nomogram, when the cancer probability cutoff value reached 0.5 there was no significant difference between 6-core biopsy and 12-core biopsy at higher risk levels; however, the difference between 6-core and 12-core biopsy at lower risk levels was significant. The tumor volume ratio of the prostate may explain this. This ratio is smaller at lower risk levels, requiring the use of concentrated biopsy cores. In patients diagnosed with malignancy, the positive rate regarding the 13th core biopsy of hypoechoic masses detected using ultrasound was significantly higher than any biopsy core obtained using systemic 12-core biopsy (70.9% vs. 56.6%; P < 0.001). In summary, taking the threshold value as being a cutoff value of 0.5, 6-core biopsy was found to be adequate for patients at higher risk levels (cutoff >0.5), and 12-core biopsy was found to be adequate for the other patients. If there are hypoechoic lesions on ultrasound, performing an extra core biopsy would be helpful. This new biopsy scheme was found to reduce the number of biopsies required and did not decrease the positive core rate in the second stage of our study.
Unfortunately, our nomogram is not the first to have been developed in China. But our nomogram was based on twice the number of patients used in former nomograms involving Chinese populations (Table
4); this may have led to more reliable results. Furthermore, our nomogram has greater clinical applicability. We could roughly predict the positive core rate, ratio of positive cores and Gleason score at every risk level. Finally, with the help of our nomogram, we identified those high-risk patients in which we could reduce the number of biopsy cores by half.
Table 4
Comparison between our nomogram and the earlier Chinese nomogram
| 535 | 44.8 | 0.848 | 0.797 | 0.051 |
Our model | 1104 | 41.5 | 0.853 | 0.761 | 0.092 |