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

Abstract

14633 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. There is little published data on HDR alone. We report our results with HDR alone. Methods: Between 1997 and 2006, 167 patients with T1 and T2 localized prostate underwent TRUS guided interstitial implant. There were no Gleason Score or PSA exclusions. No patient received EBRT 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. Treatment volume included the prostate and seminal vesicles in all cases. Our protocol for HDR alone, has called for two HDR Implants. 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 64 months (range: 6 months to 112 months), PSA disease free survival was 89.8% (150/167). Urethral stricture requiring dilatation has developed in 4.2% (7/167) of patients. Urinary stress incontinence has occurred in 3.6% (6/167). RTOG late bladder toxicities were: 0% Grade 4, 0% Grade 3, and 3.6% (6/167) Grade 2. RTOG late rectal toxicities were: 0.6% (1/167) Grade 4, 0% Grade 3, 1.8% (3/167) Grade 2, and 2.4% (4/167) Grade 1. There have been no cases of rectal incontinence to date. Conclusions: Five year results with HDR implant alone compare favorably to EBRT, LDR ± EBRT, and HDR + EBRT, both with regard to PSA disease free survival, and complications. HDR offers other advantages over LDR, such as no radiation exposure to hospital personnel, no seed migration, greater dose flexibility and precision of radiation dose delivery. Larger volumes can be treated with HDR. By omitting EBRT, bladder and rectal complications appear to be significantly reduced. No significant financial relationships to disclose.