Impalpable invisible stage T1c prostate cancer: characteristics and clinical relevance in 100 radical prostatectomy specimens--a different view.

Purpose: We analyzed 100 consecutive radical prostatectomy specimens to evaluate the extent and clinical relevance of the stage T1c cancers discovered.
Materials and Methods: All cases were diagnosed by systematic prostatic puncture biopsies because of abnormal prostate specific antigen (PSA) or PSA density. Surgical specimens were examined with the whole organ multiple step-section technique (4 mm.) to identify primary tumor location (peripheral or transition zone cancer), tumor volume, tumor volume divided by prostate volume (percent tumor volume), Gleason score, pathological T stage and positive surgical margins. Tumors smaller than 0.5 cm.3 and without unfavorable pathology (Gleason score 7 or more, or positive surgical margins) were considered insignificant.
Results: Median patient age, PSA, tumor volume and Gleason score were 64 years, 8.8 micrograms./l., 1.6 cm.3 and 6, respectively. Of the specimens 46 (46%) had transition zone cancer that was clinically undetectable due to anterior location, while peripheral zone cancers were small, diffuse, anterolateral or in large glands with low percent tumor volume. Transition zone cancer showed greater PSA, PSA density, tumor volume and percent tumor volume than peripheral zone cancer (p = 0.08, 0.03, 0.0002 and 0.0004, respectively), yet with similar Gleason score (p = 0.4). Of the tumors 34 (34%) were locally advanced (stage pT3 and/or positive surgical margins, mostly anterior in 16 transition zone cancers, and apical or posterolateral in 18 peripheral zone cancers), whereas 22 were insignificant (6 transition and 16 peripheral zone cancers). Prostatic puncture biopsies with a core cancer length of less than 3 mm. could have predicted 18 of 19 insignificant tumors but underestimated 13 (33%) and 6 (17%) significant transition and peripheral zone cancers.
Conclusions: The majority of our stage T1c tumors were significant with a distinguished high incidence of transition zone cancer. Therefore, they were large but occult. Transition zone cancer behaved differently than peripheral zone cancer, and warranted considerations during treatment of stage T1c prostate carcinoma.