Salvage high-intensity focused ultrasound ablation for prostate cancer local recurrence after external-beam radiation therapy: prognostic value of prostate MRI.

AIM: To assess the prognostic value of magnetic resonance imaging (MRI) before salvage high-intensity focused ultrasound (HIFU) for locally recurrent prostate cancer after external-beam radiotherapy (EBRT).
MATERIALS AND METHODS: Forty-six patients who underwent prostate MRI before salvage HIFU for locally recurrent prostate cancer after EBRT were retrospectively studied. HIFU failure was defined as a prostate-specific antigen (PSA) value >nadir + 2 ng/ml (Phoenix criteria) or positive follow-up biopsy or initiation of any other salvage therapy. The following prognostic parameters were assessed: neoadjuvant hormone therapy, clinical stage and Gleason score of recurrence, PSA level and velocity at HIFU treatment, and six MRI-derived parameters (prostate volume, tumour volume, extracapsular extension, seminal vesicle invasion, tumour extension into the apex or anterior to the urethra).
RESULTS: Two factors were significant independent predictors of salvage HIFU failure: the PSA level at HIFU treatment (p < 0.012; risk ratio: 1.15, 95% CI: 1.03-1.29) and the tumour extension anterior to the urethra, as assessed by MRI (p = 0.046, risk ratio: 2.51, 95% CI: 1.02-6.16).
CONCLUSION: The location of cancer recurrence anterior to the urethra on MRI is an independent significant predictor of salvage HIFU failure for locally recurrent prostate cancer after EBRT. Therefore, MRI may be useful for patient selection before post-EBRT salvage HIFU ablation.