Purpose: Little is known about the incidence rate and clinical relevance of prostate cancer in a low prostate specific antigen (PSA) level. In a prospective PSA based screening study we investigated the incidence and clinicopathological features of prostate cancer that occurred within PSA range 1 to 3 ng./ml. when the free-to-total ratio was 0.20 or less.
Materials and methods: Men participating in the Aarau, Switzerland, section of the European Randomized Study of Screening for Prostate Cancer between October 1998 and July 2000 were included in the study. As a side study, all men with PSA between 1 and 3 ng./ml. and free-to-total ratio 0.20 or less were invited to undergo further evaluation with ultrasound guided sextant prostate biopsy.
Results: Overall, 168 (7.8%) participants fulfilled inclusion criteria. A total of 158 (94%) patients underwent prostate biopsy, and prostate cancer was detected in 17 (10.8%). There were no statistically significant differences between prostate cancer and benign prostatic hyperplasia in regard to patient age (60.7 versus 59.8 years), prostate volume (23.9 versus 23.0 cc), PSA (1.98 versus 1.86 ng./ml.), free-to-total ratio (0.161 versus 0.160), PSA density (0.089 versus 0.076 ng./ml.) or PSA transition zone density (0.33 versus 0.24 ng./ml., respectively). Median Gleason score was 5 on prostate biopsy versus 6 on retropubic prostatectomy specimen. Of the 14 patients who underwent surgery there were positive lymph nodes in 1, stage pT3b Gleason 7 disease in 1, and pathologically organ confined Gleason 5 in 2, Gleason 6 in 5 and Gleason 7 in 5. Mean tumor volume was 1.01 cc (range 0.02 to 5.17). There were 2 (14.3%) insignificant (less than 0.2 cc, Gleason grade 3 or less), 1 (7.1%) minimal (less than 0.5cc, Gleason grade 3 or less) and 11 (78.6%) clinically relevant and potentially harmful cancers.
Conclusions: There is a significant number of prostate cancer cases diagnosed at PSA as low as 1 to 3 ng./ml. A majority of these tumors are clinically significant. This free-to-total ratio range may be helpful for identifying prostate cancer. The "window of opportunity" for detection of curable cancer may change in populations with higher life expectancy towards lower PSA. Lack of specificity and characterization of tumor aggressiveness remains an unsolved issue for PSA.