Prognostic model for predicting survival in men with hormone-refractory metastatic prostate cancer.
OBJECTIVE
To develop and validate a model that can be used to predict the overall survival probability among metastatic hormone-refractory prostate cancer patients (HRPC).


METHODS
Data from six Cancer and Leukemia Group B protocols that enrolled 1,101 patients with metastatic hormone-refractory adenocarcinoma of the prostate during the study period from 1991 to 2001 were pooled. The proportional hazards model was used to develop a multivariable model on the basis of pretreatment factors and to construct a prognostic model. The area under the receiver operating characteristic curve (ROC) was calculated as a measure of predictive discrimination. Calibration of the model predictions was assessed by comparing the predicted probability with the actual survival probability. An independent data set was used to validate the fitted model.


RESULTS
The final model included the following factors: lactate dehydrogenase, prostate-specific antigen, alkaline phosphatase, Gleason sum, Eastern Cooperative Oncology Group performance status, hemoglobin, and the presence of visceral disease. The area under the ROC curve was 0.68. Patients were classified into one of four risk groups. We observed a good agreement between the observed and predicted survival probabilities for the four risk groups. The observed median survival durations were 7.5 (95% confidence interval [CI], 6.2 to 10.9), 13.4 (95% CI, 9.7 to 26.3), 18.9 (95% CI, 16.2 to 26.3), and 27.2 (95% CI, 21.9 to 42.8) months for the first, second, third, and fourth risk groups, respectively. The corresponding median predicted survival times were 8.8, 13.4, 17.4, and 22.80 for the four risk groups.


CONCLUSIONS
This model could be used to predict individual survival probabilities and to stratify metastatic HRPC patients in randomized phase III trials.
Halabi
Susan
S
Department of Biostatistics and Bioinformatics and CALGB Statistical Center, Duke University Medical Center, Durham, NC 27710, USA. susan.halabi@duke.edu
Small
Eric J
EJ
Kantoff
Philip W
PW
Kattan
Michael W
MW
Kaplan
Ellen B
EB
Dawson
Nancy A
NA
Levine
Ellis G
EG
Blumenstein
Brent A
BA
Vogelzang
Nicholas J
NJ
D000230:Adenocarcinoma / Q000401:mortality*; D000368:Aged; D000726:Androgen Antagonists / Q000627:therapeutic use; D019008:Drug Resistance, Neoplasm; D006801:Humans; D008297:Male; D015233:Models, Statistical; D009362:Neoplasm Metastasis; D011379:Prognosis; D016016:Proportional Hazards Models; D011471:Prostatic Neoplasms / Q000401:mortality*; D012372:ROC Curve; D012307:Risk Factors
D000726:Androgen Antagonists