Prostate specific antigen at the initial diagnosis of metastasis to bone in patients after radical prostatectomy

Among men with biochemical progression after radical prostatectomy little is known about prostate specific antigen at the time of metastasis to bone in hormone naïve patients. This information would be useful in determining when to initiate androgen deprivation therapy.

From a large radical prostatectomy series we identified 193 hormone naïve men in whom bone metastases developed at a mean of 6 years postoperatively. We examined the prostate specific antigen distribution at bone scan conversion by time from radical prostatectomy to metastasis. ANOVA and linear regression were also used to examine the association of clinicopathological tumor features with prostate specific antigen at bone metastasis.

Median prostate specific antigen was 31.9 ng/ml at the initial diagnosis of metastatic disease. Bone scan conversion occurred at a prostate specific antigen of less than 10, 10 to 100 and greater than 100 ng/ml in 50 (25.9%), 98 (50.8%) and 45 (23.3%) men, respectively. Lower prostate specific antigen at diagnosis, higher prostatectomy Gleason scores and shorter time to metastasis were associated with lower prostate specific antigen at bone metastasis, whereas prostate specific antigen at metastasis was not significantly associated with other clinicopathological features.

Prostate specific antigen at the time of bone scan detected metastasis is highly variable. Unlike the pretreatment setting when metastases are rare at a prostate specific antigen of less than 10 ng/ml, 25.9% of bone metastases after radical prostatectomy occurred at a prostate specific antigen of less than 10 ng/ml. Because metastasis may occur at a low prostate specific antigen, patients with biochemical progression managed expectantly need regular bone scans even if prostate specific antigen is low to detect metastasis before symptoms.