(S053) Nodal Surveillance With Diffusion-Weighted MRI After Definitive (Chemo) Radiotherapy for HPV-Predominant Squamous Cell Cancers of the Oropharynx and Unknown Primary

April 30, 2015

Early surveillance imaging with diffusion-weighted MRI at 6–8 weeks following definitive treatment with radiotherapy is feasible and may be predictive of early nodal failure. Further validation in a prospective cohort is warranted.

Yao Yu, MD, Marc Mabray, MD, William Silveira, MD, PhD, Peter Y. Shen, MD, PhD, William Ryan, MD, Alina Uzelac, DO, Sue S. Yom; University of California, San Francisco

BACKGROUND: Diffusion-weighted MRI has been proposed as a method to differentiate treatment effect from persistent or recurrent nodal disease after definitive treatment with radiotherapy.

METHODS: Records and imaging were reviewed for 70 patients treated with definitive radiotherapy with or without chemotherapy for squamous cell carcinomas of the oropharynx or p16-positive unknown primary of the head and neck. A total of 40 patients were available for analysis. Surveillance imaging with magnetic resonance imaging (MRI) was obtained 6–8 weeks after treatment, followed by positron emission tomography/computed tomography (PET/CT) at 12 weeks after treatment. Apparent diffusion coefficient (ADC) values were calculated for each node and for each hemineck. PET/CT results and ADC values were correlated with regional control at 6 months based on histopathology and clinical follow-up.

RESULTS: The mean ADC was significantly lower for lymph nodes corresponding with recurrent disease compared with control at 6 months (1,301 μm2/s vs 2,049 μm2/s; P = .04). Using receiver operating characteristic (ROC) analysis, an optimal threshold of 1,600 μm2/s was identified; lymph nodes with ADC values below this threshold were found to be at higher risk for recurrent disease. Sensitivity and specificity were 100% and 84%, respectively, with positive and negative predictive values of 41% and 100%, respectively. When analyzed by hemineck, the sensitivity and specificity were 100% and 85%, respectively. PET/CT at 12 weeks yielded a sensitivity and specificity of 100% and 85%, respectively. On Kaplan-Meier analysis, ADC was predictive of nodal progression-free survival (P = .00023).

CONCLUSION: Early surveillance imaging with diffusion-weighted MRI at 6–8 weeks following definitive treatment with radiotherapy is feasible and may be predictive of early nodal failure. Further validation in a prospective cohort is warranted.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org