Dosimetic quality and evolution of edema after prostate brachytherapy for small prostates: Implications for the use of newer isotopes.

232 Background: Prostate brachytherapy is often avoided in men with small prostate volumes (PV) due to concerns about suboptimal dosimetry. We characterized prostate swelling and dosimetry in patients with small PVs compared with large PVs. Methods: We studied twenty-five patients with PV =25 cc (range 25.0-66.2) who underwent brachytherapy. Gland size was based on the contoured volume on a 3D transrectal ultrasound before the procedure. Ultrasound-guided brachytherapy was performed under intra-operative planning with loose Iodine-125 seeds to a prescription dose of 145 Gy. Patients underwent CT and MRI scans on post-implant Days 1 and 30 for dosimetric study. MRI was used to contour the prostate and then fused with the CT for dosimetry. Results: Small PVs had greater Day 1 post-implant swelling than patients with large PVs (32.5% increase in volume vs. 23.7%, p=0.04) but Day 30 swelling was minimal and not significantly different (4.4% increase in...