Interstitial high dose rate (HDR) brachytherapy alone for early stage prostate cancer

Abstract

4729 Background: Transrectal Ultrasound (TRUS) guided interstitial implant for prostate cancer using Low Dose Rate (LDR) and High Dose Rate (HDR) technique has been reported with results comparing favorably to surgery and External Beam Radiation Therapy (EBRT). Often, HDR and LDR interstitial implant is combined with EBRT. We report our results with HDR alone. Methods: Between 1997 and 2004, 137 patients with T1 and T2 prostate cancer underwent TRUS guided interstitial implant. No patient received XRT or Hormonal Blockade. Median Gleason Score was 7 (range: 4 to 10). Median PSA was 9.3 (2.7 to 39.8). Treatment volumes ranged from 42 cm3 to 196 cm3. Two HDR Implants were performed, spaced 4 weeks apart. The treatment volume received 2,250 cGy in 3 fractions prescribed to the 100% Isodose line, given over 24 hours. A 2nd implant was performed 4 weeks later, delivering a further 2,250 cGy in 3 fractions, bringing the final dose to the prostate to 4,500 cGy in 6 fractions. Urethral dose points (12–16) were followed, and limited to ≤ 105% of the prescription dose. Results: With a median follow-up of 48 months (range: 6 months to 92 months), PSA disease free survival was 91.9% (126/137). Acute urinary retention occurred in 3.6% (5/137) of the patients, requiring temporary insertion of an indwelling foley catheter. Deep venous thrombosis occurred within one month of HDR in 2.2% (3/137). Urethral stricture requiring dilatation has developed in 2.9% (4/137). Urinary stress incontinence has occurred in 1.5% (2/137). RTOG late bladder toxicities were: 0% Grade 4, 0% Grade 3, and 2.9% (4/137) Grade 2. RTOG late rectal toxicities were: 0.7% (1/137) Grade 4, 0% Grade 3, 1.5% (2/137) Grade 2, and 2.2% (3/137) Grade 1. Conclusions: Preliminary results with HDR implant alone compare favorably to EBRT, LDR +/- EBRT, and HDR + EBRT, both with regard to PSA disease free survival, and complications. By omitting EBRT, bladder and rectal complications appear to be significantly reduced. No significant financial relationships to disclose.