Interstitial High Dose Rate (HDR) Brachytherapy as Monotherapy for Early-stage Prostate Cancer: Median 8 Year Results in 321 Patients

Abstract

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. Between 1997 and 2010, 321 patients with T1 and T2 localized prostate underwent TRUS guided interstitial implant, under spinal anesthetic or local anesthetic. There were no Gleason Score or PSA exclusions. No patient received EBRT or hormonal blockade. Median Gleason Score was 7 (range, 4 – 10). Median PSA was 9.3 (2.7 – 39.8). Treatment volumes ranged from 32 cm3 – 196 cm3. Treatment volume included the prostate and seminal vesicles in all cases. Radiation treatment planning was performed using CT scanning and the Nucletron Plato Treatment Planning System. Our IRB protocol for HDR alone, has called for two HDR Implants, spaced 4 weeks apart. The treatment volume received 2250 cGy in 3 fractions prescribed to the 100% Isodose line, given over 24 hours. A second implant was performed 4 weeks later, delivering a further 2250 cGy in 3 fractions, bringing the final dose to the prostate to 4500 cGy in 6 fractions. Urethral dose points (12 – 16) were followed, and limited to ≤105% of the prescription dose. With a median follow-up of 102 months (range, 6 months – 176 months), PSA disease-free survival was 88.8% (285/321). Actuarial 8 year PSA disease-free survival was 86%. The actuarial 8 year PSA disease-free survivals by risk group, were 94% for low-risk, 86% for intermediate-risk, and 65% for high-risk. The procedure was well tolerated, with all patients having completed the procedure. Acute and chronic complications were uncommon. Acute urinary retention occurred in 5.3% (17/321) of the patients, requiring temporary insertion of an indwelling Foley catheter. Urethral stricture requiring dilatation has developed in 5.9% (19/321) of patients. Urinary stress incontinence has occurred in 2.8% (9/321). RTOG late bladder toxicities were: 0% Grade 4, 0% Grade 3, and 2.8% (9/321) Grade 2. RTOG late rectal toxicities were: 0.6% (2/321) Grade 4, 0% Grade 3, 0.9% (3/321) Grade 2, and 1.2% (4/321) Grade 1. Eight-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.