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MO_14_2818 - Consensus Radiation Therapy Contouring Guidelines for Glioblastoma, Based on NRG Recommendations

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Consensus Radiation Therapy Contouring Guidelines for Glioblastoma, Based on NRG Recommendations
T. J. Kruser1, W. R. Bosch2, S. N. Badiyan3, J. A. Bovi4, A. J. Ghia5, M. M. Kim6, S. Sachdev7, A. A. Solanki8, C. Tsien2, T. J. C. Wang9, M. P. Mehta10, and K. P. McMullen11; 1Department of Radiation Oncology, Northwestern University Feinberg School of Medicine, Chicago, IL, 2Department of Radiation Oncology, Washington University, St. Louis, MO, 3University of Maryland Medical Center, Baltimore, MD, 4Medical College of Wisconsin, Milwaukee, WI, 5Dept. of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 6Department of Radiation Oncology, University of Michigan, Ann Arbor, MI, 7Department of Radiation Oncology, Northwestern University Robert H. Lurie Comprehensive Cancer Center, Chicago, IL, 8Loyola University Medical Center, Maywood, IL, 9Department of Radiation Oncology, Columbia University Medical Center, New York, NY, 10Miami Cancer Institute, Baptist Health South Florida, Miami, FL, 11Columbus Regional Health, Columbus, IN

Purpose/Objective(s): NRG protocols for glioblastoma allow for clinical target volume (CTV) reductions at natural barriers to tumor growth; however, no guidelines have been delineated to review the relevant white matter pathways and the aforementioned barriers. This study proposes contouring guidelines based on consensus CTVs, with a focus on practical contouring concerns and common errors in glioblastoma target volume delineation.

Materials/Methods: Four postoperative glioblastoma cases in varying locations in the brain were selected. Ten academic radiation oncologists specializing in brain tumor treatment contoured CTVs on each case. CTV expansions were based on NRG trial guidelines. Contour consensus was assessed and summarized by kappa statistics. A followup meeting was held to discuss the observations and form consensus recommendations.

Results: Contours of the cavity plus enhancement (mean kappa 0.69) and T2-FLAIR signal (mean kappa 0.74) showed moderate to substantial agreement. After generating the 2-cm expansion beyond the T2-FLAIR, experts were asked to trim off anatomic barriers, and with respect to pathways of spread, develop their CTVs. Submitted CTV_4600 (mean kappa 0.80) and CTV_6000 (mean kappa 0.81) contours showed substantial to near perfect agreement. This trimming reduced the amount of total brain tissue planned for radiation targeting by a mean of 66.4 cc (range 33.1-103.8 cc) which represented a mean proportional reduction of the planned volume of 14.0% (range 7.5% - 20.4%). Recommended areas for close scrutiny of target delineation were described, and case representations of these issues are presented with relevant STAPLE contours depicted.

Conclusion: Consensus contouring guidelines were established based on expert contours. Careful delineation of anatomic pathways and barriers to spread in glioblastoma contouring can spare unnecessary radiation to uninvolved tissue without compromising target coverage. Further study is necessary to accurately define optimal target volumes beyond isometric expansion techniques for individual patients.

Author Disclosure: T.J. Kruser: Employee; Northwestern Memorial Hospital. Consultant; Varian Medical Systems. Advisory Board; Abbvie Inc. W.R. Bosch: Research Grant; National Cancer Institute. Honoraria; Augmenix, Inc. Travel Expenses; AAPM. S.N. Badiyan: None. J.A. Bovi: None. M.M. Kim: Research Grant; EpicentRx. S. Sachdev: None. C. Tsien: Speaker's Bureau; Merck. Advisory Board; Novocure. Chair Oncologic Imaging and Therapies Task Force; RSNA. Vice-Chair Education; ASTRO. T.J. Wang: Honoraria; Elekta, Wolthers Kluwer. Consultant; Abbvie, Merck, Doximity, Elekta. Advisory Board; American Cancer Society North Jersey, AstraZeneca. Travel Expenses; Abbvie, AstraZeneca, Elekta. Stock Options; Doximity. M.P. Mehta: Consultant; Agenus, Insys, Remedy, IBA, Varian, Oncoceutics, Astra-Zeneca, Celgene, Tocagen. DSMB member; Monteris. CNS Committee Chair; NRG Oncology. Board of Directors; PCG. K.P. McMullen: Consultant; Via Oncology.

Tim Kruser, MD

Northwestern Memorial Hospital

Biography:
Tim J Kruser, MD is a radiation oncologist from Northwestern Memorial Hospital in Chicago IL. He focuses on the treatment of both benign and malignant brain tumors, lung cancer, and brain metastases. His current research efforts focus on radiosurgery and stereotactic radiation techniques, integration of palliative services into the radiation oncology clinic, and collaborative clinical trial efforts with surgeons and medical oncologists.

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