title: Spot-scanning beam proton therapy vs intensity-modulated radiation therapy for ipsilateral head and neck malignancies: a treatment planning comparison.
abstract: Radiation therapy for head and neck malignancies can have side effects that impede quality of life. Theoretically, proton therapy can reduce treatment-related morbidity by minimizing the dose to critical normal tissues. We evaluated the feasibility of spot-scanning proton therapy for head and neck malignancies and compared dosimetry between those plans and intensity-modulated radiation therapy (IMRT) plans. Plans from 5 patients who had undergone IMRT for primary tumors of the head and neck were used for planning proton therapy. Both sets of plans were prepared using computed tomography (CT) scans with the goals of achieving 100% of the prescribed dose to the clinical target volume (CTV) and 95% to the planning TV (PTV) while maximizing conformity to the PTV. Dose-volume histograms were generated and compared, as were conformity indexes (CIs) to the PTVs and mean doses to the organs at risk (OARs). Both modalities in all cases achieved 100% of the dose to the CTV and 95% to the PTV. Mean PTV CIs were comparable (0.371 IMRT, 0.374 protons, p = 0.953). Mean doses were significantly lower in the proton plans to the contralateral submandibular (638.7 cGy IMRT, 4.3 cGy protons, p = 0.002) and parotid (533.3 cGy IMRT, 48.5 cGy protons, p = 0.003) glands; oral cavity (1760.4 cGy IMRT, 458.9 cGy protons, p = 0.003); spinal cord (2112.4 cGy IMRT, 249.2 cGy protons, p = 0.002); and brainstem (1553.52 cGy IMRT, 166.2 cGy protons, p = 0.005). Proton plans also produced lower maximum doses to the spinal cord (3692.1 cGy IMRT, 2014.8 cGy protons, p = 0.034) and brainstem (3412.1 cGy IMRT, 1387.6 cGy protons, p = 0.005). Normal tissue V10, V30, and V50 values were also significantly lower in the proton plans. We conclude that spot-scanning proton therapy can significantly reduce the integral dose to head and neck critical structures. Prospective studies are underway to determine if this reduced dose translates to improved quality of life.
authors.affiliation: Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX.
authors.forename: Shravan
authors.initials: S
authors.lastname: Kandula
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Zhu
authors.forename: Adam S
authors.initials: AS
authors.lastname: Garden
authors.forename: Michael
authors.initials: M
authors.lastname: Gillin
authors.forename: David I
authors.initials: DI
authors.lastname: Rosenthal
authors.forename: Kie-Kian
authors.initials: KK
authors.lastname: Ang
authors.forename: Radhe
authors.initials: R
authors.lastname: Mohan
authors.forename: Mayankkumar V
authors.initials: MV
authors.lastname: Amin
authors.forename: John A
authors.initials: JA
authors.lastname: Garcia
authors.forename: Richard
authors.initials: R
authors.lastname: Wu
authors.forename: Narayan
authors.initials: N
authors.lastname: Sahoo
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Frank
mesh_terms: D000230:Adenocarcinoma / Q000532:radiotherapy; D000328:Adult; D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000532:radiotherapy*; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D061766:Proton Therapy; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated
keywords: Head and neck malignancies; Proton therapy; Radiation therapy; Single field uniform dose optimization; Spot scanning