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

Research Original Investigation

Survival in Carcinoma of the Minor Salivary Gland

M alignant neoplasms of the salivary gland account for 3% to 6%of all head and neck cancers, 1,2 andmalig- nant neoplasms of the minor salivary gland (MSG) account for 10% to 20% of all salivary cancers. 2-6 Most of the 500 to 1000minor salivary glands are located in the oral cav- ity and oropharynx. 5 Investigators 3,4,7 have reported that as many as 80% of MSG tumors are malignant compared with theirmajor salivary gland counterparts. These tumors canpre- sent themselves ina very elusive fashionbecause of thehetero- geneity in subsite andhistologic subtype. The standard therapy for these tumors is primary surgery with or without adjuvant radiotherapy, depending on factors such as stage, histologic grade, and margin status. 6-13 A large variety ofMSGhistologic subtypes exist, eachwith its own distinct clinical behavior. The diverse histologic sub- types and the rarity of thesemalignant neoplasms havemade gathering sufficient prognostic data difficult. Some case se- ries address prognosis; however, these are restricted to 1 to 2 subsites or histologic subtypes and/or have limited case numbers. 2,4,14,15 Survival data are also inconsistent in terms of reported survival end points, whichmakes comparison and interpretation difficult. Reported 5- and 10-year cause- specific survival (CSS) rates range from 69% to 87% and 49% to 80%, respectively. 14-17 In addition to tumor stage, data sug- gest that other factors such as age, histologic subtype, and tu- mor grade and subsite may have implications for CSS rates. 9,12-20 Definitive data to guide the head and neck oncolo- gist in counseling patients about the prognosis of these ma- lignant neoplasms are lacking. The primary objective of the present studywas to examine 5- and 10-year CSS rates forMSG carcinoma across all histologic subtypes and head and neck tumor subsites in theUnited States using the Surveillance, Epi- demiology, and End Results (SEER) database from January 1, 1988, toDecember 31, 2009. Asecondaryobjectivewas to iden- tify any differences in surgical treatment and radiotherapy trends during the study period. We selected all cases of MSGmalignant neoplasms diagnosed from January 1, 1988, to December 31, 2009, from the Na- tional Cancer Institute’s SEER cancer registry using codes from the International Classification of Diseases for Oncology, Third Edition ( ICD-O-3 ) 21 for the following malignant neoplasms of the salivary gland: mucoepidermoid carcinoma (MEC) (code 8430), adenoid cystic carcinoma (ACC) (code 8200), adeno- carcinoma (codes 8140, 8147, 8290, 8310, 8410, 8440, 8480, 8525, and 8550), mixed subtype (codes 8980 and 8981), and other rare carcinomas (codes 8012, 8041, 8082, 8562, and 8982). The adenocarcinoma category included entities such as acinic cell carcinoma, polymorphous low-grade adenocar- cinoma, adenocarcinoma not otherwise specified (NOS), and other rare adenocarcinomas. The SEER database collects and publishes cancer incidence and survival data frompopulation- based cancer registries covering approximately 28%of the US population. The database contains information on patient de- Methods Data Sources and Study Participants

mographics, tumor site, histologic subtype, date and source of diagnosis, date of death, and treatment. 22,23 Because SEER is a publicly available database, which is not considered hu- man subjects research based on the Department of Health and Human Service’s Office of Human Research Protection, insti- tutional reviewboard approval was not required for the study. Demographic, clinical, and pathologic characteristics of adult patients diagnosed as havingMSG carcinoma fromJanu- ary 1, 1988, to December 31, 2009, were extracted from the SEER database. The total analytic cohort included 5334 pa- tients. Patients with no follow-up (75 [1.4%]), missing diag- nostic confirmation (11 [0.2%]), or lacking race/ethnicity des- ignation (45 [0.8%]) were excluded from the analyses. Follow-up was completed on December 31, 2009. Demographic characteristics included age (18-34, 35-44, 45-54, 55-64, 65-74, 75-84, or ≥85 years), sex (male or fe- male), race (white, black, Hispanic, Asian or Pacific Islander, or other or unknown), and socioeconomic statusmeasured by residence in a county with a high level of poverty (no, yes, or missing). Clinical characteristics included year of diagnosis (1988-1994, 1995-1999, 2000-2004, or 2005-2009), SEERstage (local, regional, distant, or missing), surgery (no surgery, total surgery, partial surgery, local tumor destructionor biopsy only, or missing), and radiotherapy (no, yes, or missing). The SEER Summary StagingManual 2000 was used in all analyses. 24 We performed additional analyses to identify any differences in surgical treatment and radiotherapy trends during the study period. Total surgery refers to complete removal of the pri- mary lesion (eg, total parotidectomy, radical parotidectomy, or total removal of salivary glands); partial surgery , partial re- moval of the primary lesion (eg, subtotal parotidectomy, re- moval of a superficial salivary gland lobe); and local tumor de- struction , minimally ablative approaches using photodynamic therapy, cryosurgery, electrocautery, or laser therapy. These surgical therapies are defined according to the third edition of the SEER Program Code Manual . 25 Pathologic features includedhistologic subtype (MEC, ACC, adenocarcinoma, or other rare carcinomas), subsite (larynx, nasal cavity and/or paranasal sinus, oral cavity, or pharynx), and lymph node examination (LNE) (no, yes, ormissing). Data for LNEwere included in the database beginning in 1988. Low- and high-grade classification (low indicates well or moder- ately differentiated; high, poorly differentiated or undifferen- tiated; or missing) was only applied to adenocarcinoma NOS because this subtype could be graded accurately based on the differentiation scheme available in the SEER data. Grade was not applied toother subtypes of adenocarcinoma,MEC, or ACC because these subtypes have their own specific grading crite- riaunrelated todifferentiation.Histologicdiagnoseswerebased on the 2005 World Health Organization classification of ma- lignant salivary gland tumors. 26 Statistical Analysis Data were analyzed from August 5, 2013, to July 1, 2014. Sta- tistical analysiswas performedusing SAS software (version9.2; SAS Institute Inc). We used 2-tailed t tests to evaluate associa- tions between primary site and histologic subtype by sociode- mographic characteristics. Statistical significance was de-

JAMA Otolaryngology–Head & Neck Surgery January 2016 Volume 142, Number 1 (Reprinted)

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