PATHOLOGY

Positive-Block Ratio in Radical Prostatectomy Specimens Is an Independent Predictor of Prostate-Specific Antigen Recurrence
Marks RA, Lin HQ, Koch MO, Cheng L
Indiana University, Indianapolis, IN and Yale University, New Haven, CT, USA
Mod Pathol. 2007; 20(suppl. 2): 163A

• Background: Tumor volume has been considered an important variable in determining the probability of disease progression in prostatic adenocarcinoma. There have been many studies that have tried to determine an appropriate method of calculating tumor volume, but no single methodology has been agreed upon. We tested the hypothesis that the ratio of tumor positive tissue blocks to the total number of blocks submitted (positive-block ratio) can be used as an independent prognostic indicator for disease recurrence.
• Design: We analyzed 504 patients who underwent total radical retropubic prostatectomy between 1990 and 1998. None of the patients had preoperative radiation or androgen-deprivation therapy. Clinical records were reviewed.
• Results: The mean positive-block ratio was 0.44 (median, 0. 43; range, 0.05-1.0). The positive block-ratio was significantly associated with Gleason score, pathologic stage, surgical margin status, extraprostatic extension, seminal vesical invasion, lymph node metastasis, perineural invasion, and preoperative serum PSA level (all P < 0.001). Using a multivariate Cox regression model, controlling for pathological stage, Gleason score, and surgical margin status, positive-block ratio was an independent predictor of PSA recurrence (hazard ratio, 2.4; 95% confidence interval, 1.1-5.1; P = 0.02). Five-year PSA recurrence-free survival was 67% for those patients with positive-block ratio 0.43, as compared to 42% those with positive-block ratio > 0.43 (P < 0.001).
• Conclusions: Positive-block ratio is an independent predictor of PSA recurrence and we recommend that this variable be recorded in radical prostatectomy specimens.
  
  
• Editorial Comment
  One of the most controversial aspects of the pathologic assessment of radical prostatectomy specimens is the measurement of tumor volume (1). No accepted standard exists for reporting cancer volume in prostatectomy specimens (2). Some institutions have calculated tumor volume accurately using computer-assisted image analysis systems. Because this method is not feasible for routine clinical practice, other investigators have proposed alternative simpler means of measuring tumor volume including diameter of largest tumor focus, number of tumor foci, number of involved blocks, percentage of blocks involved, use of a grid with 3.0 mm squares, or naked eye examination of the glass slides after the pathologist had circled all microscopically identifiable foci of carcinoma with a marking pen (the pathologist’s percentage estimate) (3-7). The method for evaluating tumor extent applied and proposed in the study by Marks et al. is based in the positive-block ratio and is a simple one and accessible to all general pathologists. Actually is easier than the one we proposed based on a point count method (8).
  Numerous studies have documented that tumor extent, volume and percentage of prostatic tissue involved by tumor within the prostate gland are important prognostic indicators. Tumor extent has been correlated with histologic grade, clinicopathologic stage, extraprostatic extension, seminal vesicle invasion, metastasis, tumor progression, and patient survival rate (6).
  Although most authors agree that tumor size (percentage of carcinoma or tumor volume) in patients with prostate carcinoma should be reported in radical prostatectomies because of its prognostic importance, in some analyses, tumor size has not been considered to be an independent predictor of tumor recurrence (1,9). In the study surveyed, Marks et al. have shown that the 5-year biochemical-free progression was 67% for those patients with positive-block ratio 0.43, as compared to 42% for those with positive-block ratio > 0.43 (p < 0.001) and that the positive-block ratio is an independent predictor of biochemical progression.

References

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Dr. Athanase Billis
Full-Professor of Pathology
State University of Campinas, Unicamp
Campinas, São Paulo, Brazil
E-mail: athanase@fcm.unicamp.br