Prostate-specific antigen doubling time among Japanese men in an annual health screening program.

Abstract

Prostate-specific antigen doubling time (PSA-DT) has been studied as a parameter reflecting the biological doubling rate of clinically localized prostate cancer treated expectantly. With the use of PSA-DT, we studied the natural history of PSA changes among Japanese men in a health screening program. Between July 1994 and December 2002, a cohort of 1995 men aged 40-79 years underwent a total of 5700 PSA measurements in an annual multiphasic health screening program. Prostate-specific antigen doubling time was calculated using a log-linear regression model for 994 (49.8%) men who had three or more serial PSA measurements with a mean follow-up of 46.2 months. Of the 994 men, 192 (19.3%) had a PSA-DT of less than 10 years and 12 (1.2%) had a PSA-DT of less than 2 years. Median PSA-DT in 14 men with a subsequent diagnosis of prostate cancer was 41.6 months (range, 12.2 to stable). A log-linear model statistically fitted 65 of 180 non-cancer patients with a PSA-DT of less than 10 years. The percentages of statistically fit cases increased with higher baseline PSA (5.3%, 7.7% and 8.7% among men with <1.0, 1.0-1.99 and 2.0-3.99 ng/mL, respectively) and older baseline age (3.7%, 8.5% and 6.9% among ages 40-49, 50-59 and 60 or older, respectively). In a small but significant portion of men, PSA increases exponentially when it is still less than 4.0 ng/mL, with a PSA-DT of less than 10 years. The clinical significance of this finding should be evaluated by a prospective screening including biopsy.