PURPOSE: To evaluate the association between post-treatment biopsy results and the probability of biochemical disease-free survival (bDFS).
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METHODS AND MATERIALS: 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 20ng/mL or Gleason score 6 and PSA level of 10-20ng/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+2ng/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 0.08ng/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%.
D'Alimonte L, Helou J, Sherman C, Loblaw A, Chung HT, Ravi A, Deabreu A, Zhang L, Morton G. Are you the author?
Department of Radiation Therapy, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; University of Toronto, Toronto, Ontario, Canada; University of Toronto, Toronto, Ontario, Canada; Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; University of Toronto, Toronto, Ontario, Canada; Department of Anatomic Pathology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada; University of Toronto, Toronto, Ontario, Canada; Department of Medical Physics, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. .
Reference: Brachytherapy. 2014 Nov 25. pii: S1538-4721(14)00676-X.