Salvage Radiotherapy After Postprostatectomy Biochemical Failure: Does Pretreatment Radioimmunoscintigraphy Help Select Patients with Locally Confined Disease?

Purpose: Radioimmunoscintigraphy (RIS) has the potential to demonstrate early recurrences after prostatectomy and might be useful in selecting patients for salvage radiotherapy (RT). Methods: A total of 82 patients with adenocarcinoma of the prostate were treated with salvage RT between 1988 and 2005, for an elevated prostate-specific antigen (PSA) level after prostatectomy. Of the 82 patients, 32% had Gleason score 6 or less disease, 54% Gleason score 7 disease, 70% had Stage pT3 disease, 55% had positive margins, and 5% had pathologic lymph node involvement. The median pre-RT PSA level was 0.63 ng/mL. Of the 82 patients, 47 (57%) had a pre-RT RIS (ProstaScint) scan, which was used for both patient selection and target delineation. The RT regimen was a median dose of 66 Gy to the prostate bed. Also, 64% received androgen deprivation therapy. Biochemical failure was defined as a PSA level >0.1 ng/mL and increasing. Results: Patients with a pre-RT RIS scan had a lower preoperative PSA level (p = 0.0240) and shorter follow-up (p = 0.0221) than those without RIS. With a median follow-up of 44 months, the biochemical control rate was 56% at 3 years and 48% at 5 years. Margin status was the only factor associated with biochemical control on univariate (p = 0.0055) and multivariate (p = 0.0044) analysis. Patients who had prostate bed-only uptake on RIS (n = 38) did not have improved outcomes, with biochemical control rates of 51% at 3 years and 40% at 5 years. Conclusion: Patients treated with salvage RT had modest responses. Patients who were selected for treatment with RIS did not have better biochemical outcomes. Our results indicated that patients with positive margins were most likely to benefit from salvage RT