2018-19 Section 7-Neoplastic and Inflammatory Diseases of the Head and Neck eBook

Lymph Node Staging for Salivary Cancer/Aro et al

not available for all patients, including tumor grade, ENE, and surgical margins. We used multiple imputation to account for this, but any methodology to account for missing data has limitations and the potential for bias. Last, the NCDB has no information regarding patterns of disease recurrence, and therefore it is not clear whether the increased mortality risk conveyed by increasing numbers of pathologic LNs is a result of regional disease recurrence, distant disease recurrence, or both. This would be an interesting topic for investigation in other large data sets of salivary cancer cases. Despite these limitations, we believe the central findings of the current study, among them that the number of positive LNs is strongly associ- ated with survival and can improve LN staging in patients with SGC, are robust. Conclusions Quantitative metastatic LN burden is strongly associated with mortality in patients with SGC, with each additional metastatic LN conferring an increased risk of death with- out plateau. Staging parameters currently in use, includ- ing LN size, contralaterality, and ENE, lack independent prognostic value when accounting for the number of met- astatic LNs. This information ultimately will help triage high-risk patients who may benefit from more aggressive adjuvant therapy. FUNDING SUPPORT Supported in part by the National Institutes of Health (grant R01 CA188480-01A1) and the National Center for Advancing Transla- tional Sciences (grants UL1TR000124 and UL1TR001881-01). CONFLICT OF INTEREST DISCLOSURES Zachary S. Zumsteg is on the external advisory board for the Scripps Proton Therapy Center and has been a paid consultant for EMD Serono for work performed outside of the current study. Katri Aro is supported by the Sigrid Juselius Foundation and the Finnish Otorhinolaryngology Research Foundation for work per- formed outside of the current study. AUTHOR CONTRIBUTIONS: Conceptualization: Allen S. Ho and Zachary S. Zumsteg . Data curation: Michael Luu and Zachary S. Zumsteg . Formal analysis: Michael Luu . Methodology: Allen S. Ho, Michael Luu, Sungjin Kim, Mourad Tighiouart , and Zachary S. Zumsteg . Supervision: Zachary S. Zumsteg . Data interpretation: All authors . Writing- original draft: Katri Aro, Allen S. Ho , and Zachary S. Zumsteg . Writing-review and editing: All authors . REFERENCES 1. Lloyd S, Yu JB, Ross DA, Wilson LD, Decker RH. A prognostic index for predicting lymph node metastasis in minor salivary gland cancer. Int J Radiat Oncol Biol Phys . 2010;76:169-175.

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