Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_31_2743 - Patterns of Failure After Postoperative Intensity-Modulated Radiation Therapy for Locally Advanced Buccal Cancer: Initial Masticator Space Involvement Is the Key Factor of Recurrence

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

Patterns of Failure After Postoperative Intensity-Modulated Radiation Therapy for Locally Advanced Buccal Cancer: Initial Masticator Space Involvement Is the Key Factor of Recurrence
Y. W. Lin1,2, Y. F. Chen3, and C. C. Yang4; 1Institute of Biomedical Science, National Sun Yat-sen University, Kaohsiung, Taiwan, 2Department of Radiation Oncology, Chi Mei Medical Center, Tainan, Taiwan, 3Department of Medical Imaging, National Taiwan University Hospital, Taipei, Taiwan, 4Department of Radiation Oncology , Chi Mei Medical Center, Tainan, Taiwan

Purpose/Objective(s): Squamous cell carcinoma (SCC) of buccal mucosa has a high incidence of locoregional failure. Its aggressive behavior and the change of lymphatic and vascular drainage after surgery make the design of the radiation treatment field difficult. The aim of this study is to analyze failure patterns and clinicopathologic prognostic factors in patients with locally advanced buccal cancer after post-operative intensity-modulated radiotherapy (IMRT).

Materials/Methods: Eighty-two patients with locally advanced (AJCC stage III/IV) buccal cancer who underwent surgery followed by post-operative IMRT between January 2007 and October 2012 were retrospectively analyzed. The high-risk clinical target volume (CTV) covered the surgical tumor bed and ipsilateral or bilateral upper neck. The low-risk CTV was ipsilateral or contralateral lower neck. The median prescribed radiation dose to high-risk CTV was 60Gy and the median dose to low-risk CTV was 54Gy.

Results: The median follow up was 51months (range, 2-112 months). 18 patients had local recurrences as the first recurrent site and 11 had supra-mandibular notch recurrences; the majority of recurrences were classified as marginal failures. There were14 patients with initial masticator space (MS) involvement. 7 of the 14 patients experienced local recurrence were all classified as supra-mandibular notch recurrences. The median time from the first local or regional recurrence to death was 5.9 months. In multivariate analyses of survivals, the initial MS involvement was the most important prognostic factor. Initial MS involvement, N2 disease, and maxillectomy were the significant prognostic predictors for supra-mandibular notch recurrences. The 5-year local failure-free, locoregional failure-free, distant metastasis-free and overall survival rates were 76%, 78%, and 58%, respectively.

Conclusion: SCC of buccal mucosa is a highly aggressive form of oral cavity cancer with a high locoregional failure rate and most locoregional recurrences led to lethal events. Post-operative IMRT for buccal cancer should not include the surgical beds alone, rather should be based on patterns of failure.

Author Disclosure: Y. Lin: None. Y. Chen: None.

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MO_31_2743 - Patterns of Failure After Postoperative Intensity-Modulated Radiation Therapy for Locally Advanced Buccal Cancer: Initial Masticator Space Involvement Is the Key Factor of Recurrence



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