The anatomy of the pelvis following robotic-assisted radical prostatectomy (RARP) is considerably different than that after open prostatectomy (OP), and these differences may have implications for postoperative radiation approaches.

As Ariel E. Hirsch, MD, and other members of a Boston University Medical Center research team noted in Practical Radiation Oncology (2011;1[2]:115-125), the current standard field design for postprostatectomy radiation is defined by the post-OP pelvis. But after comparing postoperative pelvic MRI scans from 15 consecutive RARP and 10 consecutive OP patients, the group is advising that 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.

Measurements of 13 distinct anatomic distances revealed that compared with OP patients, superior levator separation and mean resection defect measurement were greater to a statistically significant degree, and total urethral length was longer to a statistically significant degree, in the men who had undergone RARP. Vesicorectal distance also trended toward larger separation in the post-RARP group.

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“Our data support that the clinical target volume borders be expanded posteriorly and laterally in men who have undergone RARP,” concluded the researchers.