Variseed treatment planning system

Prostate mapping was performed 2-4 weeks before implantation. Imaging was done using transrectal ultrasonography (B&K Leopard 2001, BeK Medical, Wilmington, MA, USA) at 6.5 MHz. Images were recorded every 5 mm and a VariSeed treatment planning system (version 7.1, Varian, Palo Alto, CA, USA) was used with a prescribed dose of 145 Gy [9 (link), 11 (link)]. Clinical target volume (CTV) was defined as the prostate with an anterior and lateral margin of 3 mm, and a 5 mm margin in the cranial and caudal directions, with removal of the expansion into the bladder wall. No posterior margin was added at the rectal interface. For patients with Gleason 7 prostate cancer, lateral margins were 5 mm on the prostate side involved with Gleason 7 tumor [27 (link)]. Pre-plan dosimetry goals included prostate CTV V₁₀₀: > 99%, CTV D₉₀: 120-125%, and CTV V₁₅₀: 55-62% [27 (link)]. Pre-treatment plans aimed to deliver 150% of the dose to intra-prostatic regions that harbored positive biopsy cores. Pre-treatment plans were designed to keep UD5 (dose to 5% of the urethral volume) < 150%, and UD₃₀ (dose to 30% of the urethral volume) < 125% of the prescribed dose [16 (link)]. RV₁₀₀ was kept under 1 cm³.

Patients were treated with ¹²⁵I sources (model 6711; Oncura, Arlington Heights, IL and model MED3631-AM; North American Scientific, Chatsworth, CA, USA) using an implant technique that our group has previously described [20 (link)]. Briefly, a pre-operative planning ultrasound was utilized to create a modified peripheral loading pattern delivering a minimum peripheral dose of 145 Gy to the PTV. A transrectal ultrasound-guided transperineal technique under general or spinal anesthesia was used to deliver the sources. Post-operative dosimetry was assessed one month after the implant with computed tomography using the Variseed treatment planning system (Varian Medical Systems, Palo Alto, CA, USA). The Cross Cancer Institute switched from low (0.4 U) to intermediate (0.5 U) activity sources in 2002. One hundred and four (19.6%) patients received neoadjuvant hormone therapy (NHT), for a median time of 4.73 months (range 1.0–18.5 months).