Pretreatment nomogram for predicting the outcome of three-dimensional conformal radiotherapy in prostate cancer.
OBJECTIVE
Several studies have defined risk groups for predicting the outcome after external-beam radiotherapy of localized prostate cancer. However, most models formed patient risk groups, and none of these models considers radiation dose as a predictor variable. The purpose of this study was to develop a nomogram to improve the accuracy of predicting outcome after three-dimensional conformal radiotherapy.


METHODS
This study was a retrospective, nonrandomized analysis of patients treated at the Memorial Sloan-Kettering Cancer Center between 1988 and 1998. Clinical parameters of the 1,042 patients included stage, biopsy Gleason score, pretreatment serum prostate-specific antigen (PSA) level, whether neoadjuvant androgen deprivation therapy was administered, and the radiation dose delivered. Biochemical (PSA) treatment failure was scored when three consecutive rises of serum PSA occurred. A nomogram, which predicts the probability of remaining free from biochemical recurrence for 5 years, was validated internally on this data set using a bootstrapping method and externally using a cohort of patients treated at the Cleveland Clinic, Cleveland, OH.


RESULTS
When predicting outcomes for patients in the validation data set from the Cleveland Clinic, the nomogram had a Somers' D rank correlation between predicted and observed failure times of 0.52. Predictions from this nomogram were more accurate (P<.0001) than the best of seven published risk stratification systems, which achieved a Somers' D coefficient of 0.47.


CONCLUSIONS
The development process illustrated here produced a nomogram that seems to predict more accurately than other available systems and may be useful for treatment selection by both physicians and patients.
Kattan
M W
MW
Departments of Urology, Epidemiology and Biostatistics, and Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA. kattanm@mskcc.org
Zelefsky
M J
MJ
Kupelian
P A
PA
Scardino
P T
PT
Fuks
Z
Z
Leibel
S A
SA
D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use; D018572:Disease-Free Survival; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy; D011237:Predictive Value of Tests; D016016:Proportional Hazards Models; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000188:drug therapy / Q000276:immunology / Q000532:radiotherapy*; D020266:Radiotherapy, Conformal / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012306:Risk
D018931:Antineoplastic Agents, Hormonal; D017430:Prostate-Specific Antigen