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EP059/#412  NRG oncology consensus guidelines for delineation of clinical target volumes for intensity-modulated radiotherapy for intact cervical cancer
  1. Emma Fields1,
  2. Walter Bosch2,
  3. Christine Fisher3,
  4. Nrg Gyn Radiation Oncology Group1
  1. 1Virginia Commonwealth University, Radiation Oncology, Richmond, USA
  2. 2Washington University, Radiation Oncology, St. Louis, USA
  3. 3University of Colorado, Radiation Oncology, Aurora, USA


Introduction Accurate target delineation is essential when using IMRT for intact cervical cancer. In 2011, RTOG published a consensus guideline using MR images. The goal of the current project is to expand on the previous atlas by including CT-based contours without and with PET±MRI registrations, to add common and complex scenarios, and to ask about simulation and treatment planning techniques.

Methods 28 experts contoured 3 cases, first on a non-contrast CT simulation scan, then with registered diagnostic images. The cases included (1) FIGO IIIC1 with a bulky tumor and a vaginal metastasis, (2) FIGO IIB with calcified uterine fibromas, and (3) FIGO IIIC2 with large lymph nodes. The contours were analyzed for consistency using an expectation-maximization algorithm for simultaneous truth and performance level estimation (STAPLE) with kappa statistics as a measure of agreement.

Results Analysis of the contours showed considerable agreement between experts in each of the cases with kappa statistics of 0.67–0.72. For each case, use of diagnostic PET±MRI was associated with an increase in volume. The largest increase was in the CTV primary for Case 2 (20% increase in average volume, 64% increase in STAPLE estimate volume), which may be due to variance in registration priorities. For the third case, 92.9% of participants increased their CTVs based on the addition of the PET scan.

Conclusion/Implications Here we show the value as well as the challenges of using co-registered diagnostic imaging. The main areas of variance remain determining the superior extent of CTV coverage, coverage of the mesorectum, simulation and planning protocols.

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