Primary Salivary Type Lung Cancers in the National Cancer Database

Abstract

Background: Primary salivary type lung cancers such as adenoid cystic carcinoma (ACC) and mucoepidermoid carcinoma (MEC) are uncommon primary lung tumors that, given their rarity, remain incompletely understood. This study aimed to characterize the management and outcomes associated with these less common pulmonary malignancies. Methods: Patients in the National Cancer Database diagnosed with primary lung and bronchial (not tracheal) MEC and ACC between 2004 and 2014 were identified. Adjusted mortality risk of surgically managed patients was evaluated in multivariable Cox proportional hazards regression models. Results: In all, 699 MEC patients and 424 ACC patients were identified. The MEC tumors were smaller (mean size 3.1 cm versus 3.8 cm, p < 0.001), less likely to have lymph node metastases (16% versus 38%, p < 0.001), and less likely to undergo pneumonectomy (9% versus 39%, p < 0.001) compared with ACC. Adjusted Cox models of the surgically managed subset of MEC patients identified high tumor grade (hazard ratio [HR] 3.0, 95% confidence interval [CI]: 1.31 to 7.1, p = 0.01), tumor size greater than 4 cm (HR 6.7, 95% CI: 2.0 to 22.0, p = 0.01), and wedge resection (HR 3.7, 95% CI: 1.1 to 12.0, p = 0.03) to be associated with increased risk of death. For ACC patients, incomplete tumor resection, R1 versus R0 (HR 4.0, 95% CI: 1.5 to 10.6, p = 0.006), and distant metastases (HR 12.6, 95% CI: 2.5 to 64.4, p = 0.002) were associated with increased mortality. Conclusions: Pulmonary MEC and ACC appear to have distinct physical and oncologic attributes in the National Cancer Database. Although the overall prognosis appears to be favorable, there are subsets of primary salivary type lung cancers with increased mortality risk, and efforts should be made to completely resect these tumors.