Salvage radiotherapy after high-intensity focused ultrasound treatment for localized prostate cancer: feasibility, tolerance and efficacy.

Background: The objective of this study is to evaluate the feasibility, tolerance and efficacy of salvage external beam radiotherapy (EBRT) in persistent or recurrent prostate cancer after failed high intensity focused ultrasound (HIFU) therapy.

Methods: We reviewed data on tolerance and oncologic outcomes for all patients with biopsy-proven locally recurrent or persistent prostate cancer who underwent salvage EBRT in our department between April 2004 and June 2008. Minimum follow-up for inclusion was 2 years. Failure with EBRT was defined as biochemical relapse (Phoenix definition) or introduction of androgen deprivation therapy (ADT). Gastrointestinal and urinary toxicity and urinary stress incontinence were scored at 12 and 24 months (Radiation Therapy Oncology Group and Ingelman Sundberg rating, respectively).

Results: The mean age of the patients was 68.8 years (range: 60-79). Mean prostate-specific antigen (PSA) before EBRT was 5.57 ng/mL (range: 2.5-14.8). Median follow-up was 36.5 ± 10.9 months (range: 24-54). No patient received adjunctive ADT. The EBRT course was well-tolerated and completed by all patients. The mean PSA nadir was 0.62 ng/mL (range: 0.03-2.4) and occurred after a median of 22 months (range: 12-36). One patient experienced biochemical failure and was prescribed ADT 30 months after EBRT. The disease-free survival rate was 83.3% at 36.5 months. There was no major EBRT-related toxicity at 12 or 24 months.

Conclusions: Our early clinical results confirm the feasibility and good tolerance of salvage radiotherapy after HIFU failure. Oncological outcomes were promising. A prospective study with longer follow-up is needed to identify factors predictive of success for salvage EBRT therapy after HIFU failure.