Biochemical disease-free survival rates following definitive low-dose-rate prostate brachytherapy with dose escalation to biologic target volumes identified with SPECT/CT capromab pendetide

Abstract 

Purpose

To report biochemical disease-free survival (bDFS) after conformal brachytherapy with dose escalation to biological target volumes (BTVs) identified by Capromab Pendetide with single photon emission computed tomography and computed tomography image fusion (SPECT/CT).

Methods and materials

Two hundred thirty-nine (T1c–T3b NxM0) consecutive patients were evaluated by SPECT/CT before treatment. Intraprostatic SPECT/CT BTVs were identified and targeted for 150% dose escalation during brachytherapy seed implant (SI). Patients received either SI alone (n=150) or external beam radiation therapy (EBRT) plus SI boost (EBRT+SI) (n=89), with (n=50) and without (n=189) neoadjuvant hormone ablation therapy. Risk factors (RF) (prostate-specific antigen [PSA] >10ng/mL, Stage ≥T2b, and Gleason grade ≥7) defined risk group (RG) categories [none, 1, and ≥2 RF define low, intermediate, and high RG] for bDFS calculations using four failure criteria: American Society for Therapeutic Radiology and Oncology (ASTRO) consensus definition, PSA >1.0ng/mL (PSA >1), PSA >0.5ng/mL after nadir (PSA >0.5), and PSA nadir+2ng/mL rise in PSA clinical nadir (CN+2). Median followup was 47.2 months (range, 24.8–96.1).

Results

Seven-year actuarial bDFS rates were 88.0%, 82.1%, 80.4%, and 79.9% using the ASTRO, PSA >1, PSA >0.5, and CN+2 failure criteria, respectively. ASTRO-defined bDFS rates were 96.0%, 87.0%, and 72.5% for low, intermediate, and high RG's.

Conclusion

The data presented here demonstrate the feasibility of performing SPECT/CT BTV dose escalation in a mature series.

Keywords: ProstaScint, Brachytherapy, Radiotherapy, SPECT/CT, BTV, Prostate cancer, Survival