EVALUATION OF CHANGES IN PROSTATE-SPECIFIC ANTIGEN IN CLINICALLY LOCALIZED PROSTATE-CANCER MANAGED WITHOUT INITIAL THERAPY

Purpose: We define changes in prostate specific antigen (PSA) measurem ents with time in 49 men 71.9 +/- 7.0 years old (mean plus or minus st andard deviation) with clinically localized prostate cancer who remain untreated. Materials and Methods: We retrospectively analyzed PSA cha nges in prostate cancer patients managed by watchful waiting. In all p atients a minimum of 3 PSA levels were measured at intervals of at lea st 6 months after malignancy was diagnosed. The rate of change in seru m PSA level with time (PSA velocity) was determined using an exponenti al, log linear model. Results: In 49 patients treated conservatively m ean initial PSA level plus or minus standard deviation was 12.3 +/- 11 .1 ng./ml. and mean PSA followup during which no therapy for prostate cancer was introduced was 32.1 +/- 13.2 months. PSA levels decreased d uring the observation period in 11 of the 49 patients (22%) and median PSA doubling time in the remaining 38 was 55.7 months (range 15.1 to 994.5). There was no significant correlation between age at diagnosis, Gleason sum, initial PSA level or clinical stage and PSA velocity. Th e short-term rate of change in PSA during the first 9 months after pro state cancer was diagnosed correlated poorly with overall PSA velocity . The short-term rate of PSA change was greater than the overall rate of change in 14 of 37 patients (38%). Conclusions: There is significan t variability in the rate of change of PSA with time in men with clini cally localized prostate cancer who remain untreated. The usefulness o f serial PSA measurements in the management of watchful waiting is unc lear. Changes in PSA may not be helpful or appropriate in determining the need for therapy after a period of observation.