The nature of prostate cancer detected through prostate specific antigen based screening.

Prostate specific antigen (PSA) based screening nearly doubles the detection rate of early prostate cancer. However, it is unknown whether the additional tumors detected are medically important. Traditional clinical and pathological features associated with medically important cancer include a palpable tumor, multifocal or diffuse involvement and moderately or poorly differentiated histology. In contrast, microfocal, well differentiated tumors are considered to be possibly medically unimportant. We sought to examine the clinical and pathological tumor stage and tumor grade in 1,169 consecutive men whose prostate cancer was detected during serial PSA based screening protocols involving 24,346 men screened at 6-month intervals. Of the patients 97% had clinically localized (clinical stage T1 or T2) tumors, of which 39% were not palpable (stage T1). Of the men whose cancer was detected through initial screening who underwent surgical staging 69% had pathologically organ confined (pathological stage whose cancer was detected through initial screening pT1 or pT2) disease compared to 74% whose cancer was detected through serial screening (after an initially negative screening). Impalpable, clinically focal, well differentiated minimal tumors were noted in 16% of the men. However, only 3% of the men who underwent surgical staging had impalpable, pathologically microfocal, well differentiated minimal tumors. We conclude that the majority of tumors detected through PSA based screening have the clinical and pathological features associated with medically important prostate cancer.