title: Anatomic differences after robotic-assisted radical prostatectomy and open prostatectomy: implications for radiation field design.
abstract: OBJECTIVE
  To investigate the anatomy of the pelvis following robotic-assisted radical prostatectomy (RARP) compared to the anatomy of the pelvis following open prostatectomy (OP), and to determine if postoperative radiation field design should take surgical approach into consideration.
  
  
  METHODS
  This report is a retrospective review of the postoperative pelvic magnetic resonance imaging (MRI) scans for all OP patients (10) and all RARP patients (15) who presented consecutively to the radiation oncology clinic and subsequently underwent MRI scanning between January 2007 and December 2008. All patients who presented are included in the study. We measured 13 distinct anatomic distances, and we used t tests to examine mean differences in each of the parameters between RARP and OP and analysis of variance to examine mean differences controlling for length of follow-up MRI postsurgery (in days) and body mass index as covariates.
  
  
  RESULTS
  Of the measurements, we found that the superior levator separation is statistically significantly greater in the post-RARP group than in the post-OP group (P < .01). Similarly, the post-RARP group had a greater mean resection defect measurement (P = .01) as measured by a larger width of the bladder infundibulum. This suggests that the size of trigonal musculature defect is more pronounced after RARP. The total urethral length was statistically significantly longer in the RARP group (P = .03). The vesicorectal distance was variable depending on the location along the rectal wall but trended toward larger separation in the post-RARP group (P = .05).
  
  
  CONCLUSIONS
  The pelvic anatomy after RARP is considerably different from that after OP. The current standard field design for post-prostatectomy radiation is defined by the post-OP pelvis. Our data support that the clinical target volume borders be expanded posteriorly and laterally in men who have undergone RARP. As RARP continues to become a more widespread surgical option for the management of localized prostate cancer, radiation field design may need to be adjusted.
authors.affiliation: Department of Radiation Oncology, Boston University Medical Center, Boston, Massachusetts; Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts. Electronic address: ariel.hirsch@bmc.org.
authors.forename: Ariel E
authors.initials: AE
authors.lastname: Hirsch
authors.affiliation: Department of Radiation Oncology, Boston University Medical Center, Boston, Massachusetts.
authors.forename: John J
authors.initials: JJ
authors.lastname: Cuaron
authors.affiliation: Department of Radiology, Boston University Medical Center, Boston University Medical Center, Boston, Massachusetts.
authors.forename: Milos J
authors.initials: MJ
authors.lastname: Janicek
authors.affiliation: Department of Surgery, Boston University Medical Center, Boston, Massachusetts.
authors.forename: Kit
authors.initials: K
authors.lastname: Mui
authors.affiliation: Department of Radiation Oncology, Boston University Medical Center, Boston, Massachusetts.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Lee
authors.affiliation: Department of Urology, Boston University Medical Center, Boston, Massachusetts.
authors.forename: David S
authors.initials: DS
authors.lastname: Wang
authors.affiliation: Department of Urology, Boston University Medical Center, Boston, Massachusetts.
authors.forename: Richard K
authors.initials: RK
authors.lastname: Babayan
authors.affiliation: Department of Anatomy and Neurobiology, Boston University Medical Center, Boston, Massachusetts.
authors.forename: Ann C
authors.initials: AC
authors.lastname: Zumwalt
authors.affiliation: Department of Hematology/Oncology, Boston University Medical Center, Boston, Massachusetts.
authors.forename: Gretchen A
authors.initials: GA
authors.lastname: Gignac
authors.affiliation: Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Wen
authors.initials: W
authors.lastname: Tao
authors.affiliation: Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts.
authors.forename: Alexander
authors.initials: A
authors.lastname: Ozonoff
authors.affiliation: Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Zietman