328 - A Multicenter, Blinded, Intensity Modulated Proton Therapy Competitive Planning Study for Head and Neck Cancers: The Urgency for Guidelines and Standards
Presenter(s)
J. W. Snider III1, S. Mossahebi2, S. Ramirez3, J. K. Molitoris2, A. M. Chhabra4, M. Mundis5, M. Soike6, M. Butkus7, A. Vai8, D. Lebhertz9, B. Hartl10, M. Navratil11, S. G. Hedrick12, T. Hoene13, A. Anand14, M. B. Yusuf6, X. Zhang15, and S. J. Frank16; 1Proton International, Alpharetta, GA, 2Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, 3South Florida Proton Therapy Institute, Delray Beach, FL, 4New York Proton Center, New York, NY, 5Maryland Proton Treatment Center, Baltimore, MD, United States, 6Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, AL, 7Department of Radiation Oncology, Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, FL, 8National Center for Oncological Hadrontherapy (CNAO), Pavia, Italy, 9Centre François Baclesse, Normandie, France, 10University of Pennsylvania, Philadelphia, PA, 11Proton Therapy Center Czech s.r.o., Prague, Czech Republic, 12Thompson Proton Center, Knoxville, TN, 13Mayo Clinic, Rochester, Rochester, MN, 14Department of Radiation Oncology, Mayo Clinic, Phoenix, AZ, 15Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 16Department of Genitourinary Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX
Purpose/Objective(s): Pencil Beam Scanning/Intensity Modulated Proton Therapy (IMPT) has been recently established by Level I/Phase III randomized data as a standard of care that improves organ-at-risk (OAR) sparing and resultant toxicity while matching disease control rates. Despite lengthy and growing experiences at expert centers around the world, there is limited guidance in the literature for standard approaches to IMPT treatment planning for Head and Neck (H&N) cancers. This multicenter, blinded, IMPT planning study recruited participants from amongst the Particle Therapy Cooperative Group (PTCOG) H&N Subcommittee. The group hypothesized that significant heterogeneity in plan techniques and OAR sparing would exist even between “expert” groups.
Materials/Methods: Twelve (12) expert and experienced U.S. and European IMPT centers (US: 9; Eur: 3) volunteered to participate. Five (5) anonymized CT datasets were distributed through the precision radiation medicine company software platform with standardized clinical target volumes (CTVs) and OARs for the following disease sites: Paranasal Sinus (PNS), Nasopharynx (NPX), Oropharynx (OPX), Larynx (LRX), Parotid (PRD). Participating institutions were instructed to achieve at least 95% target coverage of each dose level (High/Mid/Low) with at least 95% of the prescribed dose at 70/63/56Gy in the worst case of 9 robust evaluation scenarios (3mm setup/3.5% range/nominal). IMPT was mandated and heterogeneity limited to 110% hot spot. Otherwise, participants were instructed to utilize their institutional standard approaches to these disease sites while pursuing maximal OAR sparing.
Results: All 12 institutions completed each of the 5 treatment plans while adhering to study guidance. Approaches to treatment planning varied vastly. The mean/median/range/standard deviation of number of treatment fields employed for each disease site were as follows: PNS (5.3/5.5/3-7/1.0); NPX (4.9/5.0/3-7/1.2); OPX (4.4/4.5/3-6/0.9); LRX (4.2/4.0/3-7/1.2); PRD (3.1/3.0/2-4/0.6). OAR doses and isodose curves varied vastly between centers due to both beam arrangement and optimization priorities (see Table 1 – Oral Cavity (OC) used as an example OAR).
Conclusion:
Abstract 328 - Table 1
| OC Mean (Gy) | Mean (Gy) | Median (Gy) | Range (Gy) | StDev |
| OCpns | 17.3 | 15.6 | 4.9 – 32.9 | 8.3 |
| OCnpx | 19.4 | 17.2 | 10.2 – 36.5 | 7.6 |
| OCopx | 18.2 | 16.3 | 7.8 – 37.2 | 8.8 |
| OClrx | 7.1 | 6.9 | 1.7 – 11.5 | 3.1 |
| OCprd | 8.2 | 9.2 | 1.4 – 12.5 | 3.5 |