Prospective Clinical Trial of Bladder Filling and Three-Dimensional Dosimetry in High-Dose-Rate Vaginal Cuff Brachytherapy

Abstract

Purpose-To investigate the impact of bladder filling state on dosimetry and determine the best bladder dosimetric parameter in vaginal-cuff brachytherapy.Materials and Methods-Twenty women received vaginal cylinder high-dose-rate (HDR) brachytherapy with each fraction followed by a planning CT scan on a prospective clinical trial. The bladder was full for fraction 2 and empty for fraction 3. Dose volume histogram (DVH) and dose surface histogram (DSH) values were generated for the bladder, rectum, and urethra. The midline maximum bladder point (MBP) and the midline maximum rectal point (MRP) were recorded. Paired t-tests, Pearson correlations, and regression analyses were performed.Results-The volume and surface area of bladder irradiated were significantly smaller when the bladder was empty than when full. Of several DVH and DSH parameters evaluated, the bladder D2cc, V50, V70 and SA50 significantly predicted the difference in empty versus full filling states. The V70 and D2cc were significantly correlated with the MBP. Bladder filling did not alter the volume or surface area of rectum irradiated. However, an empty bladder did result in the nearest point of bowel being significantly closer to the vaginal cylinder than when the bladder was full.Conclusions-In order to minimize radiation dose to the bladder, patients receiving vaginal-cuff HDR brachytherapy should be treated with an empty bladder if feasible. The MBP correlates well with the volumetric assessments of bladder dose and provides a non-invasive method for reporting maximum bladder point dose using 3D imaging. The MBP can therefore be used as a surrogate for complex dosimetry in the clinic.

Three-Dimensional Dosimetry of the Full and Empty Bladder in High Dose Rate Vaginal Cuff Brachytherapy

“…Similar results were obtained by other authors. 8 They emphasized an extremely low risk rate of toxicity. Moreover, the randomized trial comparing vaginal brachytherapy alone to pelvic irradiation (PORTEC 2) published in 2010 proved that brachytherapy is effective in ensuring vaginal control and should be a treatment of choice for patients with endometrial carcinoma of high-intermediate risk.…”

“…The volume and surface area of the bladder were investigated by Stewart et al 8 They proved that D 2 cc , V50, volume of the bladder receiving 70% or more of the dose, and the surface area of bladder receiving 50% or more of the dose significantly predicted for the difference between an empty and a full bladder. The second conclusion deducted from this study was that an empty bladder did result in the nearest point of bowel being significantly closer to the vaginal vault than when bladder was full.…”

Three-Dimensional Imaging in Gynecologic Brachytherapy: A Survey of the American Brachytherapy Society

“…Several centers have reported the use of CT-based imaging for tandem and ring or ovoid (7)(8)(9)(10)(11)(12)(13)(14), interstitial (15)(16)(17)(18), or vaginal cylinder (19) cases. The use of MRI for gynecologic brachytherapy has been reported in the U.S. (16) and in Europe (20)(21)(22)(23).…”

American Brachytherapy Task Group Report: Adjuvant vaginal brachytherapy for early-stage endometrial cancer: A comprehensive review

“…In a prospective study, Stewart et al found that bladder filling increased the maximum bladder dose and bladder volume receiving ≥ 70% of prescription dose. Bladder filling displaced the nearest bowel away from the vaginal cylinder though [107]. Hung et al showed that bladder filling decreased small bowel dose without affecting dose to the bladder, rectum, or sigmoid colon [108].…”