(P140) Comparison of Split-Field IMRT With Whole-Field VMAT and IMRT for Locally Advanced Head and Neck Cancer

Publication
Article
OncologyOncology Vol 28 No 1S
Volume 28
Issue 1S

Advances in intensity-modulated radiation therapy (IMRT) head and neck target delineation and treatment planning have led to improved sparing of organs at risk (OARs). In this study, we compare three IMRT techniques for the treatment of common cases of oropharyngeal squamous cell carcinoma.

Sean Quinlan-Davidson, MD, CM, Adam S. Garden, MD, G. Brandon Gunn, MD, Clifton D. Fuller, MD, PhD, David I. Rosenthal, MD, Jinzhong Yang, PhD, Xiaoqiang Li, PhD, Samuel Tung, MSc, William Morrison, MD, Jack Phan, MD, PhD; UT MD Anderson Cancer Center

Background: Advances in intensity-modulated radiation therapy (IMRT) head and neck target delineation and treatment planning have led to improved sparing of organs at risk (OARs). The selection of an optimal IMRT technique is an ongoing debate. Split-field IMRT (HB-IMRT) and whole-field IMRT (WF-IMRT) represent two common techniques employed for the treatment of oropharyngeal cancers. The advent of volumetric modulated arc therapy (VMAT) offers the potential for fewer monitor units and shorter delivery time. It is unclear whether dose to normal critical structures, particularly organs involved in swallow function, are affected with VMAT compared with HB-IMRT and WF-IMRT. In this study, we compare three IMRT techniques for the treatment of common cases of oropharyngeal squamous cell carcinoma.

Methods: CT of 10 patients with locally advanced oropharynx cancer treated at MD Anderson Cancer Center using HB-IMRT were replanned with WF-IMRT and VMAT. They included five base of tongue and five tonsil squamous cell carcinoma patients. The treatment plans were reviewed by a panel of radiation oncologists, and planning was performed by physicists with head and neck expertise. For each case, the planning target volume (PTV) and critical OARs were compared among the three techniques. In addition, target delineation of the pharyngeal constrictors was included. OARs were delineated according to Radiation Therapy Oncology Group (RTOG) 1016 guidelines. The larynx volume was divided into two subvolumes (supra and infra), separated at the base of the superior horn of the thyroid. For patients treated with the HB-IMRT technique, the isocenter was placed 3 mm above the arytenoids. The paired t-test was used to assess for significant differences of means.

Results: For the 10 bilateral plans, the mean dose (Gy) to the larynx was 23.2 for VMAT (range: 18.9–26.4 Gy), 22.1 for WF-IMRT (range: 17.5–28.2 Gy), and 25.4 for HB-IMRT (range: 15.4–30.8 Gy). The mean supralarynx dose (Gy) was 40.7 (range: 27.7–63.7 Gy), 41.3 (range: 27.9–64.2 Gy), and 53.7 (range: 30.2–68.0 Gy) for whole VMAT, IMRT, and split-IMRT, respectively. The mean infralarynx dose (Gy) was 17.7 (range: 11.9–23.9 Gy) for VMAT, 16.0 (range: 9.7–22.4 Gy) for IMRT, and 15.9 (range: 7.6–25.8 Gy) for HB-IMRT. The upper pharyngeal constrictors received a mean dose (Gy) of 60.1 (range: 53.1–69.7 Gy), 60.1 (range: 54.5–69.2 Gy), and 62.2 (range: 55.6–70.0 Gy), for whole VMAT, IMRT, and HB-IMRT, respectively. The middle pharyngeal constrictors received a mean dose (Gy) of 46.4 (range: 20.3–70.1 Gy) for VMAT, 47.7 (range: 20.1–70.3 Gy) for IMRT, and 57.9 (range: 31.2–70.3 Gy) for HB-IMRT. The PTV receiving > 110% of the volume was 0% for all three techniques. In all comparisons, no statistical differences were observed.

Conclusions: These preliminary data suggest that similar sparing of critical swallow structures may be achieved with VMAT as compared with traditional IMRT techniques. Further analysis is ongoing, as well as recruitment of additional patients to validate these findings and assess whether there is significant compromise of tumor coverage, dose homogeneity, or nonlaryngeal critical structures.

Articles in this issue

(P113) Age and Marital Status Are Associated With Choice of Mastectomy in Patients Eligible for Breast Conservation Therapy
(P112) Single-Institution Experience With Intrabeam IORT for Treatment of Early-Stage Breast Cancer
(P110) Breast Cancer Before Age 40: Current Patterns in Clinical Presentation and Local Management
(P111) Accelerated Partial-Breast Irradiation With Multicatheter High-Dose-Rate Brachytherapy: Feasibility and Results in a Private Practice Cohort
(P115) Breast Cancer Laterality Does Not Influence Overall Survival in a Large Modern Cohort: Implications for Radiation-Related Cardiac Mortality
(P117) Anatomical Variations and Radiation Technique for Breast Cancer
(P116) Bilateral Immediate DIEP Reconstruction and Postmastectomy Radiotherapy: Experience at a Tertiary Care Institution
(P118) Metadherin Overexpression Is Associated With Improved Locoregional Control After Mastectomy
(P119) Effect of Economic Environment on Use of Postlumpectomy Radiation Therapy for Stage I Breast Cancer
(P120) Immediate Versus Delayed Reconstruction After Mastectomy in the United States Medicare Breast Cancer Patient
(P121) Trend in Age and Racial Disparities in the Receipt of Postlumpectomy Radiation Therapy for Stage I Breast Cancer: 2004–2009
(P122) Streamlining Referring Physicians Orders With ‘Reflex Testing’ Significantly Decreases Time to Resolution for Abnormal Screening Mammograms
(P123) National Trends in the Local Management of Early-Stage Paget Disease of the Breast
(P124) Effect of Inhomogeneity on Cardiac and Lung Dose in Partial-Breast Irradiation Using HDR Brachytherapy
(P125) Breast Cancer Outcomes With Anthracycline-Based Chemotherapy for Residual Disease Burden After Full-Dose Neoadjuvant Chemotherapy and Surgery Followed by Radiation Treatment
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