| Abstract: |
Purpose: 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. Materials and Methods: This study was a retrospective, nonrandomized analysis of patients treated at the Memorial Sloan-Keltering 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. Conclusion: 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. (C) 2000 by American Society of Clinical Oncology. |
