Increasing external beam dose for T1-T2 prostate cancer: effect on risk groups.
OBJECTIVE
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
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.
Thames
Howard D
HD
Department of Biostatistics and Applied Mathematics, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, and Department of Radiation Oncology, William Beaumont Hospital, Deroit, MI, USA. hdt@odin.mdacc.tmc.edu
Kuban
Deborah A
DA
DeSilvio
Michelle L
ML
Levy
Larry B
LB
Horwitz
Eric M
EM
Kupelian
Patrick A
PA
Martinez
Alvaro A
AA
Michalski
Jeff M
JM
Pisansky
Thomas M
TM
Sandler
Howard M
HM
Shipley
William U
WU
Zelefsky
Michael J
MJ
Zietman
Anthony L
AL
D006801:Humans; D008297:Male; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012306:Risk; D017211:Treatment Failure
D017430:Prostate-Specific Antigen