title: Post-radiotherapy prostate biopsies reveal heightened apex positivity relative to other prostate regions sampled.
abstract: OBJECTIVE
  Prostate biopsy positivity after radiotherapy (RT) is a significant determinant of eventual biochemical failure. We mapped pre- and post-treatment tumor locations to determine if residual disease is location-dependent.
  
  
  METHODS
  There were 303 patients treated on a randomized hypofractionation trial. Of these, 125 underwent prostate biopsy 2-years post-RT. Biopsy cores were mapped to a sextant template, and 86 patients with both pre-/post-treatment systematic sextant biopsies were analyzed.
  
  
  RESULTS
  The pretreatment distribution of positive biopsy cores was not significantly related to prostate region (base, mid, apex; p=0.723). Whereas all regions post-RT had reduced positive biopsies, the base was reduced to the greatest degree and the apex the least (p=0.045). In 38 patients who had a positive post-treatment biopsy, there was change in the rate of apical positivity before and after treatment (76 vs. 71%; p=0.774), while significant reductions were seen in the mid and base.
  
  
  CONCLUSIONS
  In our experience, persistence of prostate tumor cells after RT increases going from the base to apex. MRI was used in planning and image guidance was performed daily during treatment, so geographic miss of the apex is unlikely. Nonetheless, the pattern observed suggests that attention to apex dosimetry is a priority.
authors.affiliation: Department of Radiation Oncology, University of Miami Miller School of Medicine, USA.
authors.forename: Kris T
authors.initials: KT
authors.lastname: Huang
authors.affiliation: Department of Radiation Oncology, University of Miami Miller School of Medicine, USA.
authors.forename: Radka
authors.initials: R
authors.lastname: Stoyanova
authors.affiliation: Biostatistics and Bioinformatics Core Resource, Sylvester Cancer Center, University of Miami Miller School of Medicine, USA.
authors.forename: Gail
authors.initials: G
authors.lastname: Walker
authors.affiliation: University of Miami Miller School of Medicine, USA.
authors.forename: Kiri
authors.initials: K
authors.lastname: Sandler
authors.affiliation: Department of Radiation Oncology, University of Miami Miller School of Medicine, USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Studenski
authors.affiliation: Department of Radiation Oncology, University of Miami Miller School of Medicine, USA.
authors.forename: Nesrin
authors.initials: N
authors.lastname: Dogan
authors.affiliation: Department of Pathology, Fox Chase Cancer Center, Philadelphia, USA.
authors.forename: Tahseen
authors.initials: T
authors.lastname: Al-Saleem
authors.affiliation: Department of Radiation Oncology, Stanford University Medical Center, USA.
authors.forename: Mark K
authors.initials: MK
authors.lastname: Buyyounouski
authors.affiliation: Department of Radiation Oncology, Fox Chase Cancer Center, Philadelphia, USA.
authors.forename: Eric M
authors.initials: EM
authors.lastname: Horwitz
authors.affiliation: Department of Radiation Oncology, University of Miami Miller School of Medicine, USA. Electronic address: APollack@med.miami.edu.
authors.forename: Alan
authors.initials: A
authors.lastname: Pollack
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D018365:Neoplasm, Residual / Q000532:radiotherapy; D011471:Prostatic Neoplasms / Q000473:pathology* / Q000532:radiotherapy; D011829:Radiation Dosage; D012307:Risk Factors
keywords: Biopsy; Failure patterns; Post-treatment; Prostate