Four-year outcomes of hypofractionated high-dose-rate prostate brachytherapy and external beam radiotherapy

Purpose: High-dose-rate (HDR) brachytherapy boost in prostate cancer allows dose escalation and delivery of higher biologically effective dose (BED). We evaluated the outcomes of intensity-modulated radiation therapy (IMRT) and HDR boost in a community setting.

Methods and materials: Between July 2003 and April 2008, 148 patients with prostate cancer were treated at Cancer Center of Irvine using two transperineal implants performed 1 week apart (22Gy delivered in four fractions divided between two insertions and delivered twice daily), followed by IMRT (50.4Gy). Hormonal therapy was given for 1 year to all patients with Gleason score of 8 or higher.

Results: Patient characteristics are as follows: median age at treatment, 71 years; American Joint Committee on Cancer Group IIB, 53%; Gleason score of 7, 41%; and Gleason score of 8 or higher, 14%. Median followup was 49 months, and median prostate-specific antigen (PSA) nadir was 0.15ng/mL. The 4-year actuarial biochemical disease-free survival (bDFS) was 96.8/81% by Phoenix/PSA lower than 0.5ng/mL criteria. According to National Comprehensive Cancer Center Clinical Practice Guidelines-defined recurrence risk groups, 4-year bDFS for low risk was 100/92.9%, intermediate risk was 100/86.7%, and high risk was 94/75.4% by Phoenix/PSA lower than 0.5ng/mL criteria. No statistically significant difference in bDFS was detected by either failure criteria based on risk group, lymph node risk, or initial PSA. Treatment was well tolerated. Subacute/late genitourinary and gastrointestinal toxicities were limited to 10% and 5%, respectively of all patients.

Conclusions: Prostate IMRT plus HDR brachytherapy boost was well tolerated with appropriate PSA response and bDFS at 4 years, demonstrated in a community setting. This treatment schema provides a high BED, comparable with hypofractionated prostate regimens previously reported in the literature. Higher BED delivery should be explored in further dose escalation studies.