Ten-year survival in patients with metastatic prostate cancer

The objective of this analysis is to identify baseline covariates that predict which patients will be long-term survivors with metastatic prostate cancer. We analyzed data from Southwest Oncology Group (SWOG) S8894, a clinical trial in men with newly diagnosed metastatic prostate cancer, to evaluate pretreatment characteristics associated with 10-year survival. There were 1286 eligible patients randomized to this study. Of these, 794 have been followed for ≥ 10.5 years and are included in the analyses. Proportional odds models were used to predict 3 survival categories (survival for < 5 years, 5 up to 10 years, and ≥ 10 years). Baseline patient and disease characteristics investigated were protocol treatment (flutamide vs. placebo), severity of disease, SWOG performance status (PS), bone pain, Gleason score, race, age, and prostate-specific antigen (PSA) level at study entry. Of the 794 evaluable patients, 77% lived < 5 years, 16% lived 5 up to 10 years, and 7% lived ≥ 10 years. Factors predicting a statistical significant association with longer survival (P < 0.05) included minimal disease, better PS, no bone pain, lower Gleason score, and lower PSA level. All but PS were also significant in multivariate analyses. However, only 13% of patients (5 of 38) who lived ≥ 10 years were correctly predicted in their survival category based on the model, whereas 98% (405 of 414) who died within the first 5 years were correctly predicted. Although statistically significant baseline characteristics were identified in this clinical trial, they did not accurately predict the survival interval to which a patient belonged.