Use of conformal high-dose rate brachytherapy for management of patients with prostate cancer: optimizing dose escalation.

PURPOSE: We reviewed our institution's experience treating patients with locally advanced prostate cancer using high-dose rate (HDR) conformal brachytherapy. Treatment technique, interim results, and toxicity are reviewed.

MATERIALS AND METHODS: From November 1991 to May 1998, 161 patients with locally advanced prostate cancer were treated on a dose escalation trial of external-beam radiation therapy (EBRT) combined with HDR conformal brachytherapy boosts. Patients with any of the following characteristics were acceptable for enrollment: pretreatment prostate-specific antigen (PSA) > or =10 ng/mL, Gleason score > or =7, or clinical stage T2b or higher. All patients received pelvic EBRT to a median dose of 46 Gy. Transperineal ultrasound-guided temporary HDR brachytherapy implant boosts were performed in the first, second, and third week of EBRT. Seventy-two patients were boosted with three implants (boost dose 5.50 to 6.50 Gy), and 89 patients received two implants (boost dose 8.25 to 10.50 Gy). All implants were placed using interactive real-time dosimetry. Biochemical failure was calculated using the American Society for Therapeutic Radiology and Oncology Consensus Panel definition. Median follow-up was 2.8 years (range 0.3-7.2).

RESULTS: The 2- and 5-year actuarial biochemical control rates were 86% and 67%, respectively. The 5-year actuarial biochemical control rates for patients with a pretreatment PSA < or =3.9, 4.0-9.9, 10.0-19.9, and > or =20.0 ng/mL were 80%, 87%, 56%, and 54%, respectively. Factors associated with biochemical failure on multivariate analysis included the pretreatment PSA, Gleason score, PSA nadir, and time to PSA nadir. A total of 6 patients (4%) developed grade 3 late toxicity consisting of urethral stricture (5 patients) or incontinence (1 patient). Forty- four patients (27%) developed impotence after radiation therapy.

CONCLUSIONS: Conformal HDR brachytherapy boosts appear to offer a safe, reproducible, and effective method of dose escalation in patients with locally advanced prostate cancer treated with RT. Interim results with this technology reveal biochemical control rates paralleling those achieved with three-dimensional conformal EBRT and other forms of treatment.