Purpose: It has been suggested that patients with prostate cancer meeting the following criteria have pathologically determined potentially biologically insignificant (PBI) tumor and therefore should be considered for observation: clinical stage T1c, PSA density <0.1 ng/mL per gram, absence of Gleason pattern 4 or 5, three or fewer biopsy cores positive for tumor, and tumor involvement of no more than 50% of any core. We compared the biochemical control rates in men meeting the above criteria to those of all low-risk patients (clinical T1c, PSA <or=15, Gleason score 2-6, no perineural invasion) to determine if these criteria reflect a low progression rate after definitive three-dimensional conformal radiation therapy.
Methods and materials: Of 352 low-risk patients treated with three-dimensional conformal radiation therapy, 42 met the criteria describing potentially biologically insignificant tumor (PBI group). Median center of prostate dose for all patients was 74 Gy. Biochemical control was defined in accordance with the ASTRO consensus definition.
Results: Biochemical control rates at 5 and 7 years were 89% and 89% in the PBI group and 86% and 84% in the remaining low-risk patients, respectively (p = 0.62).
Conclusions: In our experience, men meeting the criteria for potentially biologically insignificant tumor are not selected for a lower risk of biochemical failure and should not be specially selected for observation.