Consensus Guidelines for Delineation of Clinical Target Volumes for Intensity Modulated Radiation Therapy for Intact Cervical Cancer: An Update.

Purpose: Accurate target delineation is essential when using intensity modulated radiation therapy for intact cervical cancer. In 2011, the Radiation Therapy Oncology Group published a consensus guideline using magnetic resonance imaging (MRI). The current project expands on the previous atlas by including computed tomography (CT)-based contours, contours with MRI and positron emission tomography (PET) registrations, the addition of common and complex scenarios, and incorporating information on simulation and treatment planning techniques.
Methods and Materials: Twenty-eight experts in gynecologic radiation oncology contoured 3 cases, first on a noncontrast CT simulation scan and then with registered diagnostic scans. The cases included (1) International Federation of Gynecology and Obstetrics (FIGO) IIIC1 with a bulky tumor and vaginal metastasis, (2) FIGO IIB with calcified uterine fibromas, and (3) FIGO IIIC2 with large lymph nodes. The contours on all 6 data sets (3 CT simulations without diagnostic images and 3 with registered images) were analyzed for consistency of delineation using an expectation-maximization algorithm for simultaneous truth and performance level estimation with kappa statistics as a measure of agreement. The contours were reviewed, discussed, and edited in a group meeting prior to finalizing.
Results: Contours showed considerable agreement among experts in each of the cases, with kappa statistics from 0.67 to 0.72. For each case, diagnostic PET ± MRI was associated with an increase in volume. The largest increase was the clinical target volume (CTV) primary for case 2, with a 20% increase in volume and a 54% increase in simultaneous truth and performance level estimation volume, which may be due to variance in registration priorities. For the third case, 92.9% increased their CTVs based on the addition of the diagnostic PET scan. The main areas of variance were in determining the superior extent of CTV coverage, coverage of the mesorectum, and simulation and planning protocols.
Conclusions: This study shows the value and the challenges of using coregistered diagnostic imaging, with an average increase in volumes when incorporating MRI and PET.
Competing Interests: Disclosures Walter R. Bosch, PhD, has funding from the US NCI, Grant U24 CA 189893.
(Copyright © 2024 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.)