An analysis of clinical and treatment related prognostic factors on outcome using biochemical control as an end-point in patients with prostate cancer treated with external beam irradiation

Purpose: We reviewed our institution's experience in treating patients with clinically localized prostate cancer with external beam irradiation (RT) to determine if previously analyzed clinical and treatment related prognostic factors affected outcome when biochemical control was used as an end-point to evaluate results. Materials and methods: Between 1 January 1987 and 31 December 1991, 470 patients with clinically localized prostate cancer were treated with external beam RT using localized prostate fields at William Beaumont Hospital. Biochemical control was defined as PSA nadir <1.5 ng/ml within 1 year of treatment. After achieving nadir, if two consecutive increases of PSA were noted, the patient was scored a failure at the time of the first increase. Prognostic factors, including the total number of days in treatment, the method of diagnosis, a history of any pretreatment transurethral resection of the prostate (TURP) and the type of boost were analyzed. Results: Median follow-up was 48 months. No statistically significant difference in rates of biochemical control were noted for treatment time, overall time (date of biopsy to completion of RT), history of any pretreatment TURP, history of diagnosis by TURP, or boost techniques. Patients diagnosed by TURP had a significant improvement in the overall rate of biochemical control (P < 0.03) compared to transrectal/transperineal biopsy. The 5-year actuarial rates were 58 versus 39%, respectively. This improvement was not evident when pretreatment PSA, T stage, or Gleason score were controlled for. On multivariate analysis, no variable was associated with outcome. When analysis was limited to a more favorable group of patients (T1/T2 tumors, pretreatment PSA ≤20 ng/ml and Gleason score <7), none of these variables were significantly predictive of biochemical control when controlling for pretreatment PSA, T stage and Gleason score. Conclusions: No significant effect of treatment time, overall time, pretreatment TURP, or boost technique was noted on outcome in patients treated with conventional external beam irradiation when biochemical control was used as the end-point to evaluate results.