Impact of postprostatectomy prostate-specific antigen nadir on outcomes following salvage radiotherapy.

ABSTRACT

OBJECTIVES: To evaluate the relationship between the postprostatectomy prostate-specific antigen (PSA) nadir and the outcome of patients treated with salvage radiotherapy. METHODS: Seventy-eight patients received definitive external beam radiation for recurrence following radical prostatectomy (RP). The PSA nadir was undetectable in 41 patients (less than 0.05 ng/mL). All patients received salvage radiotherapy (median dose 66 Gy) for a median of 19 months (range 2 to 149) following prostatectomy. The median follow-up time was 25 months (range 1 to 59) from the date of completion of radiation. RESULTS: Among patients having an undetectable or detectable postoperative PSA, 78% and 68% were free of disease, respectively, at the last follow-up. At 3 years, the disease-free survival rates were 65% and 60%, respectively (P = 0.6). Overall, the disease-free survival rate at 3 years was 78% in patients with a PSA level 2 ng/mL or less at the time of radiotherapy compared to 31% with a PSA greater than 2 ng/mL (P < 0.0001). CONCLUSIONS: Many patients who never achieve an undetectable postprostatectomy PSA level may still be salvaged with therapeutic radiotherapy. The best predictor of a favorable outcome is a low (2 ng/mL or less) PSA level at the time of radiation.