REAL-TIME MAGNETIC-RESONANCE IMAGE-GUIDED INTERSTITIAL BRACHYTHERAPY IN THE TREATMENT OF SELECT PATIENTS WITH CLINICALLY LOCALIZED PROSTATE-CANCER

Purpose: This study was performed to establish the dose-localization c apability and acute toxicity of a real-time intraoperative magnetic re sonance (MR) image-guided approach to prostate brachytherapy in select patients with clinically localized prostate cancer. Methods and Mater ials: Nine patients with 1997 American Joint Commission on Cancer (AJC C) clinical stage T1cNxM0 prostate cancer, prostate-specific antigen ( PSA) < 10 ng/ml, biopsy Gleason score not exceeding 3 + 4, and endorec tal coil MR stage T2 disease were enrolled into this study. The prescr ibed minimum peripheral dose was 160 Gy to the clinical target volume (CTV), which was the MR-defined peripheral zone (PZ) of the prostate g land. Using a real-time 0.5 Tesla intraoperative MR imaging unit, 5-mm image planes were obtained throughout the prostate gland. The PZ of t he prostate gland, anterior rectal wall, and prostatic urethra were id entified on the T2 weighted axial images by an MR radiologist. An opti mized treatment plan for catheter insertion was generated intraoperati vely. Each catheter containing the (125)Iodine sources was placed unde r real-time MR guidance to ensure that its position in the coronal, sa gittal, and axial planes was in agreement with the planned trajectory. Real-time dose- volume histogram analyses were used intraoperatively to optimize the dosimetry. Results: For the 9 study patients, 89-99% ( median 94%) of the CTV received a minimum peripheral dose of 160 Gy an d greater than or equal to 95% of the volume of the prostatic urethra and 42-89% (median 70%) of the volume of the anterior rectal wall rece ived doses that were below the reported tolerance. All patients voided spontaneously within 3 h after discontinuation of the Foley catheter and no patient required more than a limited course (less than or equal to 3 weeks) of oral alpha-1 blockers for postimplant urethritis. Conc lusions: Real-time MR-guided interstitial radiation therapy provided t he ability to achieve the planned optimized dose-volume histogram prof iles to the CTV and healthy juxtaposed structures intraoperatively, wi th minimal acute morbidity. (C) 1998 Elsevier Science Inc.