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[The significance of early detection for prostate cancer in mass screening].

PURPOSE
In Mitaka city, mass screening for prostate cancer was conducted for 3 years from 1995 to 1997. Clinical stages were compared between patients found by screening and those diagnosed at our clinic during the same time. The significance of serum-free prostate specific antigen (PSA) in mass screening for prostate cancer was examined.


MATERIAL AND METHODS
A prospective clinical trial was conducted on men aged 50 years or older. The primary examination consisted of taking the international prostate symptom score, quality of life score, PSA (Tandem-R) and digital rectal examination (DRE). If PSA was greater than 4.0 ng./ml and/or if DRE suggested cancer, transrectal ultrasound-guided sextant prostate biopsies were indicated.


RESULTS
Of the men screened, 23.2% (320/1375) had serum PSA greater than 4.0 ng./ml. and/or suspicious findings on DRE. Biopsy was performed in 199 of 320 (62.1%). Cancer was detected in 21 (1.5%, 21/1375). Prostate cancer was found in one case among 154 males (0.65%, 1/154) who were screened twice or more. The cancer stage found by screening was significantly earlier than that diagnosed at the outpatient clinic (Wilcoxon's rank-sum test: p = 0.0047). Receiver operating characteristics analysis showed that the optimal free PSA-to-PSA ratio was 12%. Positive predictive value increased from 18% to 50% when free PSA-to-PSA ratio was combined with PSA.


CONCLUSION
1. Cancer detection rate was 1.5% in the mass screening in Mitaka City. 2. Cancer stage found by screening was significantly earlier than that diagnosed at the outpatient clinic. 3. Free PSA determination might eliminate unnecessary biopsies in men with PSA above 4.0 ng./ml with minimal loss of cancer detection.