Preoperative parameters to predict tumor volume in Japanese patients with nonpalpable prostate cancer.

Background: Serum prostate-specific antigen (PSA) determination has led to the increased detection of nonpalpable prostate cancer (T1c cancer). Some T1c cancers are small and may pose no threat. To examine the characteristics of patients with T1c cancer in Japan, patients treated with radical prostatectomy were reviewed. To predict potentially insignificant cancer, which is a candidate for delayed treatment, patients whose biopsy specimen showed relatively favorable features were also examined.

Methods: In 40 patients with T1c cancers treated with radical prostatectomy, the pretreatment parameters of serum PSA, PSA density, biopsy Gleason score, and number of cancer-positive cores were determined and compared with the histological features in the surgical specimens. Pretreatment parameters were also determined in patients whose biopsy Gleason score was 6 or less, and whose biopsy specimen contained one or two cancer-positive cores, with 50% or less cancer involvement in any cancer-positive cores.

Results: At the time of radical prostatectomy, 73% of patients had organ-confined disease. When insignificant cancer was defined as a volume of less than 0.5 cm3 and a Gleason score of 6 or less, in 9 of the 40 (23%) patients with clinical T1c disease, the cancer was clinically insignificant. Multiple regression analysis of the pretreatment variables, including pretreatment PSA level, PSA density, and number of cancer-positive cores demonstrated that the pretreatment PSA level and number of cancer-positive cores were independent factors that predicted tumor volume. From the biopsy features, 19 patients were assessed as having clinically insignificant disease. Nine (47%) of them had tumors of less than 0.5 cm3, whereas 2 (11%) had tumors of more than 2 cm3. The values for pretreatment PSA density and PSA density adjusted for the transition zone volume for those with a cancer volume of 0.5 cm3 or more were significantly higher than the values for those patients with a cancer volume of less than 0.5 cm3.

Conclusion: T1c cancers in Japanese patients included various cancers, from clinically insignificant to locally advanced ones. Pretreatment PSA level and the number of cancer-positive cores are useful parameters with which to predict cancer volume in the surgical specimen.