170 in the range of 2.6-4.0 ng/ml [24]. When the PSA cutoff value is decreased, early diagnosis of prostate cancer is theoret- ically possible, and good outcomes may be obtained. This may increase the detection rate of clinically unimportant cancers with a low disease stage and low histologic grade, however, which nonsignificantly affect patients’ prognoses even if the cancers are unidentified. This may cause un- necessary treatment of prostate cancer and complications. Furthermore, it is controversial whether lowering the PSA cutoff value will reduce the mortality of total prostate cancer. 　According to the study by Gretzer and Partin in Ameri- cans, the detection rate of prostate cancer was 25% in pa- tients with PSA in the range of 4-10 ng/ml, whereas accord- ing to the study by Lee et al in Koreans, the detection rate of prostate cancer was 15.9% [25,26]. In this study, the de- tection rate of prostate cancer was 14.9% (177/1,187) in the patients with PSA of 4-10 ng/ml, which is lower than the 25% rate in the United States but similar to the 15.8% rate in Korea. The detection rate of prostate cancer in patients with PSA ＜4 ng/ml was 9.6%, which is lower than the 12.4% reported in the study by Lee et al in Koreans [26]. The lower detection rate of prostate cancer in Koreans is likely attributable to the low morbidity of prostate cancer. 　Bozeman et al reported that a high PSA level is asso- ciated with prostate cancer diagnosis, although the PSA level in their study was less than 4 ng/ml in patients who showed abnormal findings in their DRE. Their study fur- ther reported that the patient’s age is also a predictive fac- tor of prostate cancer [27]. Al-Azab et al reported that a smaller prostate size is associated with prostate cancer in patients with PSA of 2.0-9.0 ng/ml [28]. In addition, Stephan et al reported that for a PSA ＜4 ng/ml, the PSAD showed a better performance than tPSA or %fPSA for prostate can- cer detection, and that the AUC was 0.739 for PSA of 2-4 ng/ml. They suggested that the cutoff value be 0.06 ng/ml/cc when the diagnostic sensitivity of prostate cancer is 90% or higher and 0.05 ng/ml/cc when the diagnostic sensitivity of prostate cancer is 95% or higher [29]. 　The results of this study showed that although PSA, as a predictive factor for prostate cancer, was less associated with prostate cancer in patients with PSA ≤4 ng/ml, the patient’s age was important and there was an increased possibility of getting a positive result in the prostate needle biopsy as the patient’s age increased. When the patient’s age was divided into 59 years or less, 60-69 years, and 70 years or more, the detection rates were 4.6%, 12%, and 10.9%, respectively. In addition, the results of this study showed that higher age and smaller prostate volume are associated with prostate cancer in patients with PSA of 2.0-2.9 ng/ml, wherein the PSAD is considered a useful pre- dictor, consistent with the aforementioned study results. In this study, for the PSA range of 2.0-2.9 ng/ml, the AUCs of prostate volume and PSAD were 0.813 and 0.749, respectively. It was possible to set the sensitivity of the di- agnosis of prostate cancer as 90% or higher when the pros- tate volume was ≤36 cc and the PSAD was ≥0.06 ng/ml/cc, Korean J Urol 2011;52:166-171 Kim et al which is consistent with the results of the study of Stephan et al [29]. The patient’s age will be useful in determining the need to perform a prostate needle biopsy in patients with PSA ≤4 ng/ml. A prostate needle biopsy will be re- quired for early diagnosis of prostate cancer in patients with higher age, prostate volume ≤36 cc, and PSAD ≥0.06 ng/ml/cc among patients with PSA of 2.0-2.9 ng/ml. Only the PSA 2.0-2.9 ng/ml group showed significance for age, prostate volume, and PSAD. First, at the PSA level of 0.0-1.9 ng/ml, the number of patients was too small. In the analysis performed at the PSA level of 2.0-4.0 ng/ml, the patients’ age was a significant predictor (62.6 vs. 66.9 years old, p=0.040). In this study, we believe that age is clearly a predictor of prostate cancer. Table 3 shows that in the BPH group, prostate volumes are nearly the same even if the PSA level increases, whereas in the prostate cancer group, prostate volume increased as the PSA level increased. It is believed that although the prostate volume of the pro- state cancer group was lower than that of the BPH group at the PSA level of 3.0-4.0 ng/ml, the prostate volume of the prostate cancer group increased as much as that of the BPH group in accordance with the increase in PSA level. Thus, no significant difference was observed in the prostate vol- ume between the two groups. As such, at the PSA level of 3.0-4.0 ng/ml, prostate volume and PSAD were not sig- nificantly correlated with prostate cancer. 　This study had some limitations. First, the subject size was relatively small and the subject diversity was low due to the sourcing of the data from a single hospital. Thus, a multi-center study that includes patients with various characteristics will be required in the future. Second, pa- tients who showed abnormal findings in their TRUS or DRE, or who had a higher PSA level than the age-adjusted PSA level, were chosen, but they do not represent the whole patient group with PSA ≤4 ng/ml. Third, referring to the study of Ellis et al, which showed that among patients who were not diagnosed with prostate cancer in the initial pros- tate biopsy, 20% were diagnosed with prostate cancer when subjected to a repeat prostate biopsy, there is a possibility that prostate cancer would be diagnosed in patients who were negative in the prostate needle biopsy that was con- ducted in this study if the prostate needle biopsy were re- peated [30]. Despite the aforementioned limitations, this study is valuable in that it proposed criteria for active screening to improve the detection rate of prostate cancer in patients with PSA ≤4 ng/ml. CONCLUSIONS Among patients with PSA ≤4 ng/ml, the age of the patients who showed abnormal findings in their DRE or TRUS or with a PSA level higher than the age-adjusted PSA level was a significant predictive factor for prostate cancer. In the aforementioned patients, the possibility of detecting prostate cancer increased as age increased. In particular, for the PSA range of 2.0-2.9 ng/ml, more thorough screen- ing tests for prostate cancer should be performed in pa-