Increasing external beam dose for T1-T2 prostate cancer: effect on risk groups

Int J Radiat Oncol Biol Phys. 2006 Jul 15;65(4):975-81. doi: 10.1016/j.ijrobp.2006.02.043. Epub 2006 Jun 5.


Purpose: The aim of this study was to investigate effect of increasing dose on risk groups for clinical failure (CF: local failure or distant failure or hormone ablation or PSA>or=25 ng/ml) in patients with T1-T2 prostate cancer treated with external beam radiotherapy.

Methods and materials: Patients (n=4,537) were partitioned into nonoverlapping dose ranges, each narrow enough that dose was not a predictor of CF, and risk groups for CF were determined using recursive partitioning analysis (RPA). The same technique was applied to the highest of these dose ranges (70-76 Gy, 1,136 patients) to compare risk groups for CF in this dose range with the conventional risk-group classification.

Results: Cutpoints defining low-risk groups in each dose range shifted to higher initial PSA levels and Gleason scores with increasing dose. Risk groups for CF in the dose range 70-76 Gy were not consistent with conventional risk groups.

Conclusions: The conventional classification of risk groups was derived in the early PSA era, when total doses<70 Gy were common, and it is inconsistent with risk groups for patients treated to doses>70 Gy. Risk-group classifications must be continuously re-examined whenever the trend is toward increasing total dose.

Publication types

  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Humans
  • Male
  • Prostate-Specific Antigen / blood
  • Prostatic Neoplasms / blood
  • Prostatic Neoplasms / pathology
  • Prostatic Neoplasms / radiotherapy*
  • Radiotherapy Dosage*
  • Risk
  • Treatment Failure


  • Prostate-Specific Antigen