Role of androgen deprivation therapy in early salvage radiation among patients with prostate-specific antigen level of 0.5 or less

Abstract

Background: The Radiation Therapy Oncology Group 96-01 randomized trial demonstrated the benefit of adding androgen deprivation therapy (ADT) to salvage radiotherapy for an increasing prostate-specific antigen (PSA) after prostatectomy, but it is unknown whether modern patients followed with ultrasensitive PSA and salvaged at a low PSA (ie, ≤ 0.5) also benefit from ADT.

Patients and methods: The cohort comprised 108 patients who received radical prostatectomy (RP), were followed by ultrasensitive PSA, and received salvage radiotherapy at a PSA of 0.5 or less. Sixty patients had negative margins, and 48 patients had positive margins at RP. Cox multivariable regression analysis was performed to identify factors associated with time to secondary PSA failure and included PSA at salvage, year of treatment, Gleason score, ADT use, margin status, T stage, and PSA doubling time. Occurrence of distant metastases was documented.

Results: Median follow-up after radiation was 63.09 months. A total of 24 patients had a distant metastasis. In all patients, ADT use was associated with a decreased risk of recurrence (hazard ratio [HR], 0.44; 95% confidence interval [CI], 0.25-0.79; P = .006). On subgroup analysis, ADT was associated with a decreased risk of failure among patients with negative margins (HR, 0.27; 95% CI, 0.12-0.61; P = .002), but not among men with positive margins (HR, 0.78; 95% CI, 0.29-2.10; P = .63).

Conclusions: Even patients followed with ultrasensitive PSA and salvaged early with a PSA ≤ 0.5 seem to benefit from the addition of ADT to salvage radiation. However, this benefit seemed to be limited to men with negative margins; thus, men with positive margins and PSA ≤ 0.5 may be good candidates for salvage radiation alone.

Keywords: ADT; Prostate cancer; Salvage therapy; Surgical margins; Ultrasensitive PSA.