Comparison and Consensus Guidelines for Delineation of Clinical Target Volume for CT- and MR-Based Brachytherapy in Locally Advanced Cervical Cancer

Abstract

Purpose/Objective To create and compare consensus clinical target volume (CTV) contours for computed tomography (CT) and 3 Tesla (3T) magnetic resonance (MR) image-based cervical-cancer brachytherapy Materials/Methods Twenty-three gynecologic radiation oncology experts contoured the same 3 cervical-cancer brachytherapy cases: one Stage IIB near-complete response (CR) case with a tandem and ovoid, one Stage IIB partial response (PR) case with ovoid with needles and one Stage IB2 CR case with a ring applicator. CT contours were completed before MRI contours. These were analyzed for consistency and clarity of target delineation using an expectation maximization algorithm for simultaneous truth and performance level estimation (STAPLE), with kappa statistics as a measure of agreement between participants. The conformity index (CI) was calculated for each of the six data sets. Dice coefficients were generated to compare CT and MR contours of the same case. Results For all 3 cases, the mean tumor volume was smaller on MR than on CT (p<0.001). Kappa and CI estimates were slightly higher for CT, indicating a higher level of agreement on CT. DICE coefficients were 89% for the Stage IB2 case with a CR, 74% for the Stage IIB case with a PR, and 57% for the Stage IIB case with a CR. Conclusion When comparing MR- to CT-contoured CTV volumes, the higher level of agreement on CT may be due to the more distinct contrast visible on the images at the time of brachytherapy. The largest difference at the time of brachytherapy was in the case with parametrial extension at diagnosis that had a near-complete response, due to the appearance of the parametria on CT but not on MR. Based on these results, a 95% consensus volume was generated for CT and for MR. Online contouring atlases are available for instruction at http://www.nrgoncology.org/Resources/ContouringAtlases.aspx.

Surgery Versus Radiation Treatment for High-Grade Neuroendocrine Cancer of Uterine Cervix: A Surveillance Epidemiology and End Results Database Analysis

“…26,27 Because the survival and local control outcomes of Brachytherapy is an integral part of definitive RT for cervical cancer to achieve pelvic disease control. 28 In our analysis, the addition of brachytherapy to EBRT did not improve survival for patients with cervical HGNECs. We could not assess pelvic control with the addition of brachytherapy because the endpoint was lacking in the SEER database.…”

Implementing MRI-based target delineation for cervical cancer treatment within a rapid workflow environment for image-guided brachytherapy: A practical approach for centers without in-room MRI

“…Delineation of the HR-CTV at this first fraction of IBBT is based on the examination under anesthesia and CT images obtained during this procedure. The HR-CTV includes the gross tumor and entire cervix with an effort to adhere to the recommendations of Viswanathan et al (7).…”

Magnetic Resonance–Guided Gynecologic Brachytherapy

“…Even on computed tomography (CT) scans that enable 3-dimensional (3D) planning and accurate definition of organs at risk, 9,10 cervical tumors are difficult to distinguish from surrounding scar tissue resulting from the external beam treatment that precedes brachytherapy. 11,12 The advent of remote afterloading systems allows the robotic deployment of a high-dose-rate or a pulseddose-rate source into the inside of the applicator, with the source resting for varying times at points along the applicator, creating a customized dose distribution. Nevertheless, the technical capability of delivering very precise customized dose distributions has limited value without accurate delineation of the gross tumor volume (GTV) and the surrounding areas likely containing microscopic disease (clinical target volume [CTV]).…”

“…For instance, 3 T MR is becoming more available and its use is expected to improve image quality and available resolution. Concerns regarding the applicability of existing contouring guidelines, 12 image deformation, heating of the brachytherapy equipment, and image artifacts have been raised by some investigators. 19 Experience in some major centers, notably in the Advanced Multimodality Image Guided Operating (AMIGO) suite at the Brigham and Women's Hospital in Boston, has proven the feasibility of 3 T MR-based brachytherapy.…”