title: The clinical significance of persistent cancer cells on prostate biopsy after high-dose-rate brachytherapy boost for intermediate-risk prostate cancer.
abstract: OBJECTIVE
  To evaluate the association between post-treatment biopsy results and the probability of biochemical disease-free survival (bDFS).
  
  
  METHODS
  Two sequential prospective clinical trials were undertaken in men with intermediate-risk prostate cancer (T1-T2 with either Gleason score 7 and prostate-specific antigen [PSA] level lower than 20 ng/mL or Gleason score 6 and PSA level of 10-20 ng/mL). All patients had high-dose-rate brachytherapy (two fractions of 10Gy separated by 1 week or a single 15-Gy fraction) followed by external beam radiotherapy. Both study groups were followed prospectively with regular PSA readings and prostate biopsy at 2 years. Biopsies were reported as: positive=malignant cells with no or only partial radiation effect, negative=no malignant cells seen, and indeterminate=malignant cells with marked radiation effect. Biochemical failure was defined using the nadir+2 ng/mL definition and estimated using the Kaplan-Meier curves. Fisher exact test was performed to investigate any relationships between high-dose-rate treatment and biopsy results.
  
  
  RESULTS
  A total of 181 patients were included in this analysis. The median followup for all patients was 6.2 years (range, 0.3-10.5). Post-treatment biopsy was performed in 111 patients of which 82 (74%) were negative, 17 (15%) indeterminate, and 12 (11%) malignant. The 5-year bDFS was 97.5%, 93.8%, and 83.3% for those with benign, indeterminate, and malignant biopsies, respectively (p=0.4398). Median PSA nadir was 0.08 ng/mL (range, 0.01-3.63), with no difference in PSA change over time by treatment (p=0.9953) or biopsy result (p=0.4398) CONCLUSIONS: Routine biopsy at 2 years was not able to reliably predict which patients would ultimately fail as even those with a positive biopsy had a long-term bDFS higher than 80%.
authors.affiliation: Department of Radiation Therapy, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; University of Toronto, Toronto, Ontario, Canada.
authors.forename: Laura
authors.initials: L
authors.lastname: D'Alimonte
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Joelle
authors.initials: J
authors.lastname: Helou
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Anatomic Pathology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Christopher
authors.initials: C
authors.lastname: Sherman
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Andrew
authors.initials: A
authors.lastname: Loblaw
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Hans T
authors.initials: HT
authors.lastname: Chung
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Medical Physics, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Ananth
authors.initials: A
authors.lastname: Ravi
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Andrea
authors.initials: A
authors.lastname: Deabreu
authors.affiliation: Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada.
authors.forename: Liying
authors.initials: L
authors.lastname: Zhang
authors.affiliation: University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. Electronic address: Gerard.morton@sunnybrook.ca.
authors.forename: Gerard
authors.initials: G
authors.lastname: Morton
mesh_terms: D000230:Adenocarcinoma / Q000401:mortality / Q000473:pathology* / Q000532:radiotherapy*; D001706:Biopsy; D001918:Brachytherapy / Q000379:methods*; D018572:Disease-Free Survival; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D060787:Neoplasm Grading; D011446:Prospective Studies; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000401:mortality / Q000473:pathology* / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D016896:Treatment Outcome
chemical_list: D017430:Prostate-Specific Antigen
keywords: Biochemical outcomes; Biopsy; HDR brachytherapy; Prostate