title: Location of residual cancer after transrectal high-intensity focused ultrasound ablation for clinically localized prostate cancer.
abstract: What's known on the subject ? and What does the study add? Transrectal High-Intensity Focused Ultrasound (HIFU) ablation has been used as a minimally invasive treatment for localized prostate cancer for 15 years. Five-year disease-free survival rates of 66-78% have been reported, challenging the results of external-beam radiation therapy. Usually, a 6-mm safety margin is used in the apex to preserve the urinary sphincter and potency. The influence of this 6-mm margin on the results of the treatment has never been assessed. This retrospective study of a cohort of 99 patients who underwent systematic biopsy 3-6 months after HIFU ablation for prostate cancer (with a 6-mm safety margin in the apex) shows that post-HIFU residual cancer is found more frequently in the apex. Therefore, new strategies improving the prostate destruction at the apex while preserving the urinary continence need to be found.
  
  
  OBJECTIVE
  • To evaluate whether the location (apex/midgland/base) of prostate cancer influences the risk of incomplete transrectal high-intensity focused ultrasonography (HIFU) ablation.
  
  
  METHODS
  • We retrospectively studied 99 patients who underwent prostate cancer HIFU ablation (Ablatherm; EDAP, Vaulx-en-Velin, France) with a 6-mm safety margin at the apex, and had systematic biopsies 3-6 months after treatment. • Locations of positive pre- and post-HIFU sextants were compared. • The present study included two analyses. First, sextants negative before and positive after treatment were recoded as positive/positive, hypothesizing that cancer had been missed at pretreatment biopsy. Second, patients with such sextants were excluded.
  
  
  RESULTS
  • Pre-HIFU biopsies found cancer in all patients and in 215/594 sextants (36.2%); 55 (25.6%) positive sextants were in the apex, 86 (40%) in the midgland and 74 (34.4%) in the base. • After treatment, residual cancer was found in 36 patients (36.4%) and 50 sextants (8.4%); 30 (60%) positive sextants were in the apex, 12 (24%) in the midgland and eight (16%) in the base. • Both statistical analyses found that the locations of the positive sextants before and after HIFU ablation were significantly different (P < 0.001), with a higher proportion of positive apical sextants after treatment. • At the first analysis, the mean (95% confidence interval) probability for a sextant to remain positive after HIFU ablation was 8.8% (3.5-20.3%) in the base, 12.7% (5.8-25.9%) in the midgland and 41.7% (27.2-57.89%) in the apex. • At the second analysis, these same probabilities were 5.9% (1.9-17%), 9.9% (3.9-23.2%) and 27.3% (13.7-47%), respectively.
  
  
  CONCLUSIONS
  • When a 6-mm apical safety margin is used, residual cancer after HIFU ablation is found significantly more frequently in the apex.
authors.affiliation: Hospices Civils de Lyon, Department of Urinary and Vascular Radiology, Hôpital Edouard Herriot, Lyon, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Boutier
authors.forename: Nicolas
authors.initials: N
authors.lastname: Girouin
authors.forename: Alexandre Ben
authors.initials: AB
authors.lastname: Cheikh
authors.forename: Aurélien
authors.initials: A
authors.lastname: Belot
authors.forename: Muriel
authors.initials: M
authors.lastname: Rabilloud
authors.forename: Albert
authors.initials: A
authors.lastname: Gelet
authors.forename: Jean-Yves
authors.initials: JY
authors.lastname: Chapelon
authors.forename: Olivier
authors.initials: O
authors.lastname: Rouvière
mesh_terms: D000368:Aged; D001706:Biopsy; D006801:Humans; D008297:Male; D018365:Neoplasm, Residual; D009929:Organ Size; D011467:Prostate / Q000473:pathology*; D011471:Prostatic Neoplasms / Q000473:pathology / Q000628:therapy*; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome; D036761:Ultrasound, High-Intensity Focused, Transrectal / Q000379:methods*