Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_36_2485 - The significant reduction of late Xerostomia of Intensity-modulated proton therapy for oropharyngeal cancer

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

The significant reduction of late Xerostomia of Intensity-modulated proton therapy for oropharyngeal cancer
J. Z. Cao1, X. Zhang2, B. Jiang2, J. Y. Chen2, X. R. Zhu2, G. B. Gunn3, and S. J. Frank3; 1Department of Radiation Oncology,The University of Texas MD Anderson Cancer Center, Houston, TX, Houston, TX, 2Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, 3The University of Texas MD Anderson Cancer Center, Houston, TX

Purpose/Objective(s): To compare and report the xerostomia after intensity-modulated radiation therapy (IMRT) or intensity-modulated proton therapy (IMPT) in patients with oropharyngeal cancer and investigate the dosimetric vairables leading to acute or late xerostomia

Materials/Methods: 529 oropharyngeal cancer patients received definitive radiotherapy from January 2011 to August 2015 at MD Anderson Cancer Center (425 IMRT and 104 IMPT). Each patient completed an 8-item self-reported xerostomia-specific questionnaire(XQ) and rated each item on a scale from 0 to 10; The higher the score, the worse the xerostomia. The dosimetric variables and xerostomia were compared with Chi-square test or independent sample T tests.

Results: The mean XQ scores of IMPT group were significantly lower at 18-24 and 24-36 months after radiotherapy, compared to IMRT group (22.1 vs 15.8, P=0.032; 23.1 vs 15.1, P=0.014). At 0-3、3-6、6-9、9-12 and 12-18 months after radiotherapy, the mean XQ scores were not significantly different between the two groups. The incidence of XQ scores >40 late xerostomia also was significantly lower in the IMPT group than in the IMRT group: 0% versus 17.3% at 18-24 months (P=0.043); 0% versus 23.1% at 24-36 months (P=0.012). The proportions of XQ scores >40 were similar between the two groups at 0-3、3-6、6-9、9-12 and 12-18 after radiotherapy (34.3% vs 34.1%; 32.7% vs 30.8%; 23.3% vs 20.0%; 18.3% 10.8%; 14.6% vs 12.1%). According to late xerostomia (12 months after radiotherapy), higher V5, V10, V15 and V20 on contra-lateral Parotid were significantly (p <0.05) associated to higher proportion of XQ scores >40. V5 to V50 on contra-lateral parotid are associated to acute xerostomia (0-6 months after radiotherapy). Dosimetric data on ipsi-lateral parotid was not related to both acute and late xerostomia. Compared with IMRT, IMPT delivered lower contralateral parotid V5 (76.4 % vs. 92.5%) with P<0.05 for the patients with late xerostomia data available.

Conclusion: IMPT reduces late xerostomia of patients with oropharyngeal cancer. Only contra- not ipsi- lateral parotid dosimetric data are stongly related to both acute and late xerostomia. The significant reduction of late xerostomia by IMPT might be related to lower contra-lateral V5 by IMPT.

Author Disclosure: J.z. Cao: None. J.Y. Chen: None. X. Zhu: None. G.B. Gunn: Associate Medical Director; MD Anderson Cancer Center - Proton Therapy. S.J. Frank: Research Grant; C4 Imaging, ELEKTA, U19. Founder and Director; C4 Imaging. Honoraria; ELEKTA, Varian Medican Systems, Inc. Advisory Board; Varian Medican Systems, Inc. Stock; C4 Imaging. Royalty; C4 Imaging. Patent/License Fees/Copyright; C4 Imaging. Chairman; American Brachytherapy Society. Director; C4 Imaging. Director-at-large; North America Skull Base Society.

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