Date of Award

January 2017

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Benjamin L. Judson

Abstract

Prognostic lymph node yield thresholds have been identified and incorporated into national treatment guidelines for multiple cancer sites, but not for head and neck cancers. The objective of this study was to identify optimal thresholds in elective and therapeutic neck dissection for oral cavity cancers.

To accomplish this objective, patients with oral cavity cancers in the National Cancer Database (NCDB) were stratified into clinically lymph node-negative (cN0) and clinically lymph node-positive (cN1) cohorts to reflect the differing surgical management for these diseases. Univariate and multivariate analyses were performed to assess the relation between lymph node yield and overall survival, adjusting for other prognostic factors. Thresholds derived from the NCDB were validated in the Surveillance, Epidemiology, and End Results (SEER) database.

We found that increasing lymph node yield was linearly associated with improved survival up to 35 lymph nodes when controlling for other prognostic factors. In patients with cN0 cancers of the oral cavity from the NCDB, those who had <16 lymph nodes had significantly decreased survival. The proportion of positive lymph nodes was higher for patients who had 16 lymph nodes (27.2% vs 16.3% for<16 lymph nodes; p<0.001). This threshold was validated in 2,715 lymph node-negative cancers from SEER, with a mortality hazard ratio of 0.818 for ≥16 lymph nodes (95% confidence interval, 0.695-0.963; p=0.016). In patients with cN1 oral cavity cancers from the NCDB, groups with <26 lymph nodes had significantly decreased survival. This threshold was validated in 1,903 lymph node-positive cancers from SEER, with a mortality hazard ratio of 0.790 (95% confidence interval, 0.692-0.902; p<0.001). Academic centers, higher volume centers, and geographic location predicted higher lymph node yields.

In summary, more extensive neck dissection (≥16 lymph nodes in cN0, ≥26 lymph nodes in cN1) was associated with better survival. These findings are applicable as quality metrics are established in performance measurements in healthcare. Further evaluation of practice patterns in lymph node yield may represent an opportunity for improved quality of care.

Comments

This thesis is restricted to Yale network users only. This thesis is permanently embargoed from public release.

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