CORE CANCER LENGTH IN ULTRASOUND-GUIDED SYSTEMATIC SEXTANT BIOPSIES - A PREOPERATIVE EVALUATION OF PROSTATE-CANCER VOLUME

Objectives. Evidence has been presented that biologic aggressiveness of prostate carcinoma increases with volume and that cancers less than 0.5 cc may be regarded as clinically insignificant for immediate treatment. We have analyzed the ability of core cancer length on needle biopsy to predict cancer volumes near the 0.5 cc threshold for distinction between incidental versus clinical carcinoma. Methods. Systematic sextant transrectal ultrasound-guided prostate biopsies were performed on 110 men who then underwent radical prostatectomy for adenocarcinoma. The core cancer length within each biopsy was compared with the volumes of clinical and incidental carcinomas in the prostatectomy specimen. Results. Among incidental (nonpalpable) cancers, 14% of those under 0.2 cc were detected, but 44% at 0.2 to 0.5 cc and 92% of those more than 0.5 cc were detected. Among clinically suspected Carcinomas, 2 mm or longer core cancer length reliably predicted a cancer of 0.5 cc or larger, but among incidental cancers, it predicted a tumor of 0.2 cc or larger. A 3-mm core cancer length threshold predicted 0.5 cc for both groups. The high frequency of incidental cancers under 0.5 cc impaired the predictive value of multiple positive needle cores. Bilateral positive biopsy results indicated bilateral extension of clinical cancer in only 59% of cases. Conclusions. A core cancer length of 3 mm or more on one or two needle biopsies reliably predicts cancer of clinically significant volume (0.5 cc; or larger). The high detection frequency of smaller incidental carcinomas on biopsy impairs the reliability of volume estimation from multiple positive needle cores and mandates that treatment decisions be made with knowledge of core cancer length.