Purpose: Lymph node yield is an independent prognostic factor for survival outcomes in patients receiving neck dissection for oral squamous cell carcinoma (SCC). This study investigates whether hospital case volume is associated with increased lymph node yield in neck dissection specimens.
Background: Guidelines recommending minimum number of lymph nodes that constitutes an adequate neck dissection have not been established. There is evidence that comprehensive neck dissections with improved lymph node yield ( 18 nodes) are associated with better survival outcomes. Recent studies have proposed this association to be a potential institutional-level quality metric. However, whetherinstitutional experience (reflected by case volume) influences the quality and comprehensiveness of neck dissection (reflected in node yield) remains unknown.
Methods: The National Cancer Database was used to identify 21,150 patients who underwent primary neck dissections for oral SCC diagnosed between 2004 and 2015. Average annual surgical volumes were calculated for each facility to stratify them into quartiles based on highest to lowest case volumes. A multivariable negative binomial mixed model was used to model the number of nodes examined at the patient level, which accommodated the clustering of hospitals and adjusted for clinical and demographic factors.
Results: The median lymph node yield for all hospitals was 27 (Interquartile Range [IQR] 16-40) nodes. Median lymph nodes examined for the quartile of highest volume hospitals was 29 (IQR 19-42). Compared to a lymph node yield of 18 (IQR 9-30) in the 3rd quartile, 17 (IQR 9-27) in the 2nd quartile, and 16 (IQR 8-26) in the lowest quartile. A Dwass, Steel, Critchlow-Fligner procedure indicated that the number of nodes were significantly different for all pairwise comparisons except between the lowest two quartiles.
Conclusions: These data suggest that for patients with oral SCC undergoing neck dissections, increase in hospital case volume is associated with higher lymph node yield. Institutions with greater experience and case volumes are more likely to consistently meet the cutoff value of lymph node yield ( 18 lymph nodes) in neck dissection specimens, that are shown to improve survival outcomes.
