Assessment of transposed ovarian movement: how much of a safety margin should be added during pelvic radiotherapy?

Abstract

The purpose of this study was to analyze transposed ovarian movement. Data from 27 patients who underwent ovarian transposition after surgical treatment for uterine cancer were retrospectively analyzed. Computed tomography (CT) images including transposed ovaries were superimposed on other CT images acquired at different times, and were matched on bony structures. Differences in ovarian position between the CT images were measured. The planning organ at risk volume (PRV) margins were calculated from the formula of the 90% reference intervals (RIs) and the 95% RI, which were defined as mean ± 1.65 standard deviation (SD) and mean ± 1.96 SD, respectively. The 90% RI in the cranial, caudal, anterior, posterior, left and right directions were 1.5, 1.5, 1.4, 1.0, 1.7 and 0.9 cm, respectively. The 95% RI in the corresponding directions were 1.5, 2.0, 1.7, 1.2, 1.9 and 1.2 cm, respectively. These data suggest that bilateral ovaries need a PRV margin of ∼2 cm in all directions. The present study suggests that a transposed ovary needs the same PRV margin as a normal ovary (∼2 cm). Even after transposition, ovaries should be kept away from the radiation field to take into consideration the degree of ovarian movement.

Ovarian transposition before radiotherapy in cervical cancer patients: functional outcome and the adequate dose constraint

“…The international commission on radiation units and measurements (ICRU) recommends that planning organ at risk volume (PRV) margins should be used, because uncertainties and variations in the positioning of the organ at risk (OAR) during treatment must be considered to avoid serious complications [20]. A recent study proposed that the PRV margin for transposed ovaries is ~ 2 cm in all directions [21]; however, 2 cm margins would be excessively large in many cases. When the patient is younger, and the preservation of ovarian function is required, should the dose constraint of the ovarian PRV be considered as a priority, and what is the adequate dose constraint to transported ovaries?…”

Practical recommendations for fertility preservation in women by the FertiPROTEKT network. Part II: fertility preservation techniques

“…The ovary should lie at least 2 cm above the iliac crest [ 48 ]. In addition, a safety margin of approximately 2 cm must be included, because the position of the ovaries can change postoperatively [ 49 ].…”

Robotically Assisted Laparoscopic Ovarian Transposition in Women with Lower Gastrointestinal Cancer Undergoing Pelvic Radiotherapy

“…36,37 If IMRT is implemented, the planning organ-at-risk volume (PRV) margin is 2 cm in all directions. 38 Given the risk for ovarian migration, OT should be performed as close to the time of RT as possible. 22 …”