Objectives: Metastatic prostate cancer results in significant patient morbidity, health care expenditure, and ultimately in mortality. We sought to identify patient and treatment factors predictive of distant metastases in patients completing external beam radiotherapy.
Methods: Five hundred sixty-seven patients completing external beam radiotherapy at Fox Chase Cancer Center, Philadelphia, Pennsylvania between March 1987 and November 1994 for Stage T1 to T3 tumors were analyzed. Distant metastases were detected by radionuclide bone scans. Estimates of rates for distant metastases as a first failure were conducted using cumulative incidence methods and predictors of failure were analyzed univariately and multivariately.
Results: The median follow-up was 46 months. On univariate analysis, the following were statistically significant predictors of distant metastases at 5 years: patient age greater than 65 years, pretreatment prostate-specific antigen (PSA) level, advanced stage, lower radiation dose, and Gleason score 7 to 10. Multivariate testing confirmed that age greater than 65 years, high pretreatment PSA level, lower radiation dose, and advanced stage were significant independent predictors of distant metastases.
Conclusions: Men over the age of 65 years are more likely to experience distant failure than are younger men. The discovery of age-related differences in patterns of failure has significant therapeutic implications with regard to patient selection, trial design, and adjuvant therapy recommendations. Furthermore, age-related differences in failure may influence comparison of outcome data for radiotherapy series, which tend to have older patients, to surgical reports that usually include significantly younger men.