Differential response rates to irradiation among patients with human papillomavirus positive and negative oropharyngeal cancer

Authors

  • Allen M. Chen MD,

    Corresponding author
    1. Department of Radiation Oncology, University of California, Davis, Comprehensive Cancer Center, Sacramento, California, U.S.A.
    • Department of Radiation Oncology, University of California, Davis, Comprehensive Cancer Center, 4501 X Street, Suite G140, Sacramento, CA

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  • Judy Li PhD,

    1. Department of Biostatistics Core, University of California, Davis, Comprehensive Cancer Center, Sacramento, California, U.S.A.
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  • Laurel A. Beckett PhD,

    1. Department of Biostatistics Core, University of California, Davis, Comprehensive Cancer Center, Sacramento, California, U.S.A.
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  • Talia Zhara MD,

    1. Department of Radiation Oncology, University of California, Davis, Comprehensive Cancer Center, Sacramento, California, U.S.A.
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  • Gregory Farwell MD,

    1. Department of Otolaryngology–Head and Neck Surgery, University of California, Davis, Comprehensive Cancer Center, Sacramento, California, U.S.A.
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  • Derick H. Lau MD,

    1. Department of Medical Oncology, University of California, Davis, Comprehensive Cancer Center, Sacramento, California, U.S.A.
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  • Regina Gandour-Edwards MD,

    1. Department of Pathology, University of California, Davis, Comprehensive Cancer Center, Sacramento, California, U.S.A.
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  • Andrew T. Vaughan PhD,

    1. Department of Radiation Oncology, University of California, Davis, Comprehensive Cancer Center, Sacramento, California, U.S.A.
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  • James A. Purdy PhD

    1. Department of Radiation Oncology, University of California, Davis, Comprehensive Cancer Center, Sacramento, California, U.S.A.
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  • The authors have no funding, financial relationships, or conflicts of interest to disclose.

Abstract

Objectives/Hypothesis:

To evaluate the responsiveness of human papillomavirus (HPV) -positive and HPV-negative oropharyngeal cancer to intensity-modulated radiotherapy (IMRT), using axial imaging obtained daily during the course of image-guided radiotherapy (IGRT).

Study Design:

Observational cohort study with matched-pair analysis of patients irradiated for HPV-positive and HPV-negative oropharygeal cancer.

Methods and Materials:

Ten patients treated by IMRT to 70 Gy for locally advanced, HPV-positive squamous cell carcinoma of the oropharynx were matched to one HPV-negative control subject by age, gender, performance status, T-category, tumor location, and the use of concurrent chemotherapy. The gross tumor volume (GTV) was delineated on daily IGRT scans obtained via kilovoltage cone-beam computed tomography (CBCT). Mathematical modeling using fitted mixed-effects repeated measure analysis was performed to quantitatively and descriptively assess the trajectory of tumor regression.

Results:

Patients with HPV-positive tumors experienced a more rapid rate of tumor regression between day 1 of IMRT and the beginning of week 2 (−33% Δ GTV) compared to their counterparts with HPV-negative tumors (−10% Δ GTV), which was statistically significant (p<0.001). During this initial period, the average absolute change in GTV was −22.9 cc/week for HPV-positive tumors and −5.9 cc/week for HPV-negative tumors (p<0.001). After week 2 of IMRT, the rates of GTV regression were comparable between the two groups.

Conclusions:

HPV-positive oropharyngeal cancers exhibited an enhanced response to radiation, characterized by a dramatically more rapid initial regression than those with HPV-negative tumors. Implications for treatment de-intensification in the context of future clinical trials and the possible mechanisms underlying this increased radiosensitivity will be discussed. Laryngoscope, 2013

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