Computed Tomography Consensus Clinical Target Volume Contouring for Intensity Modulated Radiation Therapy in Intact Cervical Carcinoma International Journal of Radiation Oncology, Biology, Physics ORAL SCIENTIFIC SESSION| VOLUME 96, ISSUE 2, SUPPLEMENT , S13-S14, OCTOBER 01, 2016
Date
10/01/2016Abstract
Purpose/Objective(s)
Target definition is crucial for the definitive treatment of cervix cancer with intensity modulated radiation therapy (IMRT). Consensus guidelines for the clinical target volume (CTV) have been established using magnetic resonance imaging (MRI). However, treatment planning MRI is not as readily available as computed tomography (CT) and image fusion carries inherent uncertainties. Therefore, the aim of this study was to evaluate the variability in CTV definition amongst physicians experienced in IMRT for the definitive treatment of cervical cancer in preparation for a collaborative NRG clinical trial.
Materials/Methods
A consensus working group that had participated in prior CTV definition was convened to contour on two treatment planning CT scans. Observers were blinded to the corresponding MRI scans. One case was an early cervical cancer and the other a loco-regionally advanced case. Clinical vignettes for the two cases were distributed and each participant was asked to draw CTV contours which included a CTV1 contour for the uterus/cervix and a CTV 2 contour for the vagina/parametria. Participants contoured on CT images of the pelvis using their own treatment planning software. Nodal CTV contours have been well described and were not included in this study. The CTV contours were then analyzed for consistency and clarity of target delineation using an expectation-maximization algorithm for simultaneous truth and performance level estimation (STAPLE, CERR), with Kappa statistics as a measure of agreement between observers.
Results
Contoured datasets were merged and analyzed for agreement. CTV1 contours showed almost perfect agreement (Kappa > 0.8), while CTV2 showed moderate agreement (0.4 < Kappa < 0.6) among observers (see Table 1).
Conclusion
Agreement among the experienced gynecologic radiation oncologists was excellent for CTV delineation in two representative intact cervical cancer cases. Consensus demonstrated near perfect agreement for the uterus and cervix and moderate agreement for the vagina and parametria. The variability seen in vaginal contours was primarily due to the vaginal length included in the CTV. The value of this data, building on previously published guidelines for IMRT in the post-operative setting and MRI guidance in the intact setting, provides clinically valuable information to promote safety and quality among radiation oncologists treating cervical carcinoma. Furthermore, this atlas will be used for future trials utilizing IMRT for the definitive management of intact cervical cancer.
Author List
C.M. Yashar I.A. Petersen W.R. Bosch K.V. Albuquerque S. Beriwal J.P. Chino B.A. Erickson J. Feddock D.K. Gaffney R. Iyer A.H. Klopp C. Kunos J.S. Mayadev L. Portelance A.N. Viswanathan A.H. Wolfson A. Jhingran L.K. MellAuthor
Beth A. Erickson MD Professor in the Radiation Oncology department at Medical College of WisconsinView Online
