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Original Research—Head and Neck Surgery

Otolaryngology– Head and Neck Surgery

Predictors of Nodal Metastasis in Parotid Malignancies: A National Cancer Data Base Study of 22,653 Patients

2016, Vol. 154(1) 121–130 American Academy of Otolaryngology—Head and Neck

Surgery Foundation 2015 Reprints and permission:

sagepub.com/journalsPermissions.nav DOI: 10.1177/0194599815607449 http://otojournal.org

Christopher C. Xiao 1 , Kevin Y. Zhan, MD 1 , Shai J. White-Gilbertson, PhD, MSCR 2 , and Terry A. Day, MD 1

Received July 17, 2015; revised August 26, 2015; accepted September 1, 2015. S alivary gland cancers are rare, with an estimated incidence of 1.3 per 100,000. 1 The World Health Organization classifications for salivary malignan cies contain 24 distinct histopathologies, and yet com bined, they only represent approximately 5% of all head and neck cancers. 2,3 As a result, these cancers have been historically difficult to study when histologies are pooled or studied separately by primary site. Most prior studies have been single-institution case series spanning a few decades. For purposes of statistical analysis, some combine major and minor salivary glands, despite known differ ences in composition, prognosis, behavior, and treatment between carcinomas of those locations and even among major gland sites. 4-12 The challenge of studying a myriad of rare cancers at a single primary site is simply that they are rare and the low numbers prohibit extensive analysis. Nodal metastasis in parotid gland cancers has long been shown to significantly reduce survival, and it often requires additional treatment, including neck dissection 6 radia tion. 13-16 Despite such critical treatment-related decisions, there are limited data showing the true incidence of regional metastasis for the wide assortment of histologies. Aside from clinically obvious nodal disease, large tumor size and high-grade histology are main criteria for determining need for neck dissection. 4,17,18 As such, neck dissection recom mendations range from routine prophylactic lymphadenect omy at some institutions 19 to more conservative strategies elsewhere. 20 Without accurate nodal incidence data for 1 Department of Otolaryngology–Head and Neck Surgery, Medical University of South Carolina, Charleston, South Carolina, USA 2 Cancer Registry, Hollings Cancer Center, Charleston, South Carolina, USA This article was accepted for presentation at the 2015 AAO-HNSF Annual Meeting & OTO EXPO; September 27-30, 2015; Dallas, Texas. Corresponding Author: Terry A. Day, MD, Department of Otolaryngology–Head and Neck Surgery, Medical University of South Carolina, 135 Rutledge Ave, MSC 550,

No sponsorships or competing interests have been disclosed for this article.

Abstract Objective. (1) To identify predictors of nodal disease in paro tid malignancies using various clinical and pathologic vari ables. (2) To examine the effect of nodal disease on overall survival (OS) in parotid cancers

Study Design. Retrospective database review.

Setting. National Cancer Data Base (1998-2012).

Subjects and Methods. We identified all cases of primary par otid malignancies in the United States between 1998 and 2012 in the National Cancer Data Base. Eight histopatholo gies, constituting . 80% of all cases, were examined for nodal metastasis and survival. Results. We identified 22,653 cases of primary parotid cancer. Eight major histologies were studied, with mucoe pidermoid carcinoma (31%), acinic cell carcinoma (18%), adenocarcinoma (14%), and adenoid cystic carcinoma (9%) being most common. Regional nodal disease incidence was 24.4% overall and varied by histopathology. Salivary ductal carcinoma had the highest incidence of both nodal metas tasis and occult lymph node metastasis. Overall, N0 patients lived significantly longer than N 1 (5-year OS, 79% vs 40%; P \ .001). Low-grade disease had significantly better sur vival than high-grade (5-year OS, 88% vs 69%; P \ .001). Occult nodal disease was found in 10.2% and varied by histopathology. Conclusion. Regional lymph node metastasis significantly decreases survival in many parotid malignancies. High-grade cancers had higher incidences of regional disease than did low grade. Adenocarcinoma had the highest mortality when regional disease was present. Incidence of occult disease varied by histology, but incidence was \ 10% for all low-grade disease. High T stage and grade are significant independent predictors of nodal disease for most histopathologies.

Keywords parotid cancer, nodal disease, occult disease, parotid malignancy

Charleston, SC 29425, USA. Email: headneck@musc.edu