• Sean M Vance, Matthew H Stenmark, Kevin Blas, Schulyer Halverson, Daniel A Hamstra, and Felix Y Feng.
• Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, MI 48109-5010, USA.
• Int. J. Radiat. Oncol. Biol. Phys. 2012 Jul 1; 83 (3): 940-6.

PurposeTo investigate the prognostic utility of the percentage of cancer volume (PCV) in needle biopsy specimens for prostate cancer patients treated with dose-escalated external beam radiotherapy.Methods And MaterialsThe outcomes were analyzed for 599 men treated for localized prostate cancer with external beam radiotherapy to a minimal planning target volume dose of 75 Gy (range, 75-79.2). We assessed the effect of PCV and the pretreatment and treatment-related factors on the freedom from biochemical failure, freedom from metastasis, cause-specific survival, and overall survival.ResultsThe median number of biopsy cores was 7 (interquartile range, 6-12), median PCV was 10% (interquartile range, 2.5-25%), and median follow-up was 62 months. The PCV correlated with the National Comprehensive Cancer Network risk group and individual risk features, including T stage, prostate-specific antigen level, Gleason score, and percentage of positive biopsy cores. On log-rank analysis, the PCV stratified by quartile was prognostic for all endpoints, including overall survival. In addition, the PCV was a stronger prognostic factor than the percentage of positive biopsy cores when the two metrics were analyzed together. On multivariate analysis, the PCV predicted a worse outcome for all endpoints, including freedom from biochemical failure, (hazard ratio, 1.9; p = .0035), freedom from metastasis (hazard ratio, 1.7, p = .09), cause-specific survival (hazard ratio, 3.9, p = .014), and overall survival (hazard ratio, 1.8, p = .02).ConclusionsFor patients treated with dose-escalated external beam radiotherapy, the volume of cancer in the biopsy specimen adds prognostic value for clinically relevant endpoints, particularly in intermediate- and high-risk patients. Although the PCV determination is more arduous than the percentage of positive biopsy cores, it provides superior risk stratification.Copyright © 2012 Elsevier Inc. All rights reserved.

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