The biology and natural history of prostate cancer is not completely understood. Rigorous evaluation of any prostate cancer screening modality is desirable because the natural history of the disease is variable, and appropriate treatment is not clearly defined. Although the prevalence of prostate cancer and preneoplastic lesions found at autopsy steadily increases for each decade of age, most of these lesions remain clinically undetected. An autopsy study of white and Asian men also found an increase in occult prostate cancer with age, reaching nearly 60% in men older than 80 years. More than 50% of cancers in Asian men and 25% of cancers in white men had a Gleason score of 7 or greater, suggesting that Gleason score may be an imprecise indicator of clinically insignificant prostate cancer.
There is an association between primary tumor volume and local extent of disease, progression, and survival. A review of a large number of prostate cancers in radical prostatectomy, cystectomy, and autopsy specimens showed that capsular penetration, seminal vesicle invasion, and lymph node metastases were usually found only with tumors larger than 1.4 cc. Furthermore, the semiquantitative histopathologic grading scheme proposed by Gleason is reasonably reproducible among pathologists and correlates with the incidence of nodal metastases and with patient survival in a number of reported studies.
Cancer statistics from the American Cancer Society and the National Cancer Institute indicated that between 2002 and 2008, the proportion of disease diagnosed at a locoregional stage and at a distant stage was 93% and 4% for whites, compared with 91% and 6% for African Americans, respectively. Stage distribution of prostate cancer is affected substantially by the intensity of early detection efforts.
Pathologic stage does not always reflect clinical stage and upstaging (owing either to extracapsular extension, positive margins, seminal vesicle invasion, or lymph node involvement) occurs frequently. Of the prostate cancers detected by digital rectal exam (DRE) in the pre-PSA era, 67% to 88% were at a clinically localized stage (T1-2, NX, M0 [T = tumor size, N = lymph node involvement, and M = metastasis]).[33,34] However, in one of those series of 2,002 patients undergoing annual screening DRE, only one-third of men proved to have pathologically organ-confined disease.