Head and Neck Cancer

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MO_30_2699 - Early Metabolic Response at Mid-Radiation Therapy FDG-PET Imaging Predicts Patterns of Treatment Failure in Locally Advanced Oropharyngeal Cancer

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

Early Metabolic Response at Mid-Radiation Therapy FDG-PET Imaging Predicts Patterns of Treatment Failure in Locally Advanced Oropharyngeal Cancer
R. Liang1, N. Zhang2, J. Wu1, N. Sandhu3, E. Pollom3, Q. T. Le1, W. Hara1, and R. Li1; 1Department of Radiation Oncology, Stanford University, Stanford, CA, 2Department of Radiation Oncology, Stanford University, Jinan, China, 3Stanford Cancer Institute, Stanford, CA

Purpose/Objective(s): Imaging with 18-fluorodeoxyglucose-positron emission tomography (FDG-PET) is used for staging, radiation treatment planning, and evaluation of therapy response. The purpose of this work was to assess early metabolic response at mid-radiotherapy (RT) FDG-PET imaging obtained at 30-36 Gy and investigate its ability to predict patterns of treatment failure in locally advanced oropharyngeal cancer.

Materials/Methods: We retrospectively collected data for oropharyngeal squamous cell carcinoma patients who were treated with definitive chemoradiotherapy from 2009 to 2015 at our institution and who have available pre- and mid-RT PET-CT scans. Three types of PET image features were analyzed, including SUV maximum, metabolic tumor volume (defined at a threshold of 50% of SUVmax), and total lesion glycolysis. All three features were calculated on both pre- and mid-RT PET scans. Additionally, the longitudinal change between the two scans was also computed for all image features. Cox proportional hazard regression analysis was used to evaluate the prognostic value of individual PET image features for predicting locoregional recurrence and distant metastasis. We further adjusted for clinicopathologic factors including tumor and nodal stage, HPV and smoking status in multivariate Cox regression analysis

Results: A total of 104 patients with a median follow-up of 30 months were analyzed. On univariate analysis, mid-RT MTV was the only PET imaging parameter associated with locoregional recurrence (hazard ratio [HR] = 9.6, 95% confidence interval [CI]: 1.2-76.6, P = 0.0005). On multivariate analysis, mid-RT MTV remained a significant predictor (HR = 1.5; 95% CI: 1.02-2.3, P = 0.039) for locoregional recurrence, in addition to nodal stage (HR = 7.6; 95% CI: 1.2-49.0, P = 0.032), HPV positivity (HR = 0.14; 95% CI: 0.03-0.79, P = 0.025). Both pre-RT SUVmax and the change between SUVmax pre- and mid-RT scans were associated with distant metastasis (HR = 4.1, 95% CI: 1.2-14.4, P = 0.016, HR = 3.4, 95% CI: 1.1-10.5, P = 0.026, respectively) on univariate analysis. However, there were no significant predictors for distant metastasis on multivariate analysis.

Conclusion: MTV at mid-RT PET was an independent predictor of locoregional recurrence. If validated, it may aid with individualized risk-adaptive therapy for oropharyngeal cancer.

Author Disclosure: R. Liang: None. J. Wu: None. N. Sandhu: None. Q. Le: Research Grant; Amgen, NIH, Redhill. Travel Expenses; BMS. Stock; Aldea. president elect; American Radium Society. Head and Neck Committee Chair; RTOG NRG Cooperative group. W. Hara: Member; NCI Metastatic and Recurrent Head & Neck Task Forc.

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