5 % of head and neck cancers originate from the sinonasal tract [1]. Squamous cell carcinoma (SCC) incidence is cited between 35 % to 58 % and is one of the most common histological types of sinonasal malignancy [1]. Sinonasal squamous cell carcinoma (SNSCC) most commonly originates in the maxillary sinus, with the nasal cavity being the second most common [2]. SNSCC has been associated with several known environmental exposures such as smoking, glues, adhesives, leather, and various types of wood [1,3]. As with most sinonasal primary tumors, early diagnosis is often difficult given SNSCC expands within a confined anatomic site such as the sinus, nasal cavity, or nasopharynx, and patients are asymptomatic until later in the disease process after invasion of regional or distant structures including the orbit, infratemporal fossa, and skull base, dura, and brain [[3], [4], [5]]. Patients with SNSCC typically present with nonspecific symptoms that are similar to other inflammatory or infectious diseases of the sinus cavity, such as epistaxis, rhinorrhea, nasal obstructions, orbital deformity, and facial pain [5]. This likely explains the poor survival outcomes for SNSCC, with a 5-year OS of 53 % [1,6].

According to the National Comprehensive Cancer Network (NCCN), surgery for SNSCC is recommended as the preferred treatment for T1 to T4a tumors of the ethmoid and maxillary sinuses [[7], [8], [9]]. In cases with high-risk features such as high T stage and positive surgical margins, adjuvant radiation therapy (RT) or chemoradiation (CRT) is also recommended. The optimal surgical approach (e.g., endoscopic vs open approaches) is debatable, and often depends on extent of tumor involvement, surgeon and center experience, and availability of instrumentation and resources. Surgical management through endoscopic approach has been established as safe and effective with similar outcomes compared to open approaches [[10], [11], [12], [13], [14], [15], [16]]. Open surgical management of SNSCC has traditionally been more commonly utilized than endoscopic surgical management, with recent studies indicating advances in endoscopic surgery making it safe and less invasive with comparable margin status and oncological outcomes [10,[17], [18], [19]]. Endoscopic approaches have comparable recurrence and mortality rates, operative time, intraoperative blood loss, and length of stay compared to traditional open craniofacial approaches for SNSCC [15,20]. Recently, endoscopic surgery has been shown to be associated with shorter time from surgery to initiation of adjuvant RT. [21] This, in addition to minimal invasiveness with maximal preservation of uninvolved vital structures, while also sparing external surgical incisions, has popularized endoscopic approaches over open approaches whenever feasible [22].

Outcomes and treatment of head and neck and skull base tumors have been evaluated in relation to facility volume in previous studies including laryngeal cancer, pituitary adenoma, nasopharyngeal carcinoma, esthesioneuroblastoma, among others [[23], [24], [25], [26], [27], [28], [29], [30], [31], [32]]. Additionally, a recent study analyzed the role of facility volume and all treatment modalities on OS in SNSCC; however, the impact of facility volume on OS has yet to be evaluated in patients treated with primary endoscopic surgery. Given the complexity and multidisciplinary care needed for management, this study investigates a large patient population database, the National Cancer DataBase (NCDB), to determine the impact of facility volume on survival in primary endoscopically treated SNSCC.