Abstract # 2203 Improving the Therapeutic Ratio of Prostate Brachytherapy: Dose Escalation in I-125 Prostate Implants

Presenter: Kao, Johnny

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At Mount Sinai, the prescription D90 for I-125 monotherapy has been 160 Gy (TG-43), using real-time intraoperative planning since 1997. Consequently, some patients have a D90 of ≥180 Gy at the time of post-implant dosimetry. From 6/1995 to 2/2004, 598 patients were treated with I-125 alone for T1-2 prostate cancer with a D90 of ≥180 Gy (median 197, range 180 - 267). The implants were performed using a real-time ultrasound guided seed placement method, intraoperative dosimetry and modified peripheral loading to optimize target coverage and homogeneity. A median of 92 seeds (range 31 to 220) were implanted into a prostate with a median US volume of 44.0 cc (range 14.3-125.0cc). The median activity implanted was 44.6 mCi (range 7.6-96.9 mCi) and the median V150 was 70.7% (range 21.0-94.1%). The median urethral D30 was 240.0 Gy (range 2.4-515.5 Gy) and the median rectal V100 was 1.00 cc (range 0.00-6.19 cc). The biochemical control of 435 patients that had a minimum 2 year PSA follow-up (median f/u 6.7 years; range 2.0-11.1 years) was analyzed. 9.2% of the patients were intermediate or high risk based on one or more of the following factors: PSA>10, Gleason 7-10 or T2c disease. 31% received neoadjuvant hormonal therapy. Of the 509 patients with available potency data, 375 (73.7%) were potent prior to implant. Longitudinal urinary function was assessed in 249 patients with pretreatment IPSS and a follow-up IPSS at least 3 years after implant (median 4.5 years, range 3-10 years). Post-brachytherapy prostate biopsy results were available for 120 (20.1%) patients.

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