Abstract
Purpose: Salivary gland cancer (SGC) in the oral cavity is not common and has been less studied in comparison with oral squamous cell carcinoma (SCC). This study aimed to identify the clinical characteristics and outcomes of SGC in the oral cavity compared with oral SCC.Methods: The medical charts of the patients with SGC (N = 68) arising from minor salivary glands and SCC (N = 750) in the oral cavity between 1995 and 2017 were reviewed retrospectively. The clinical and pathological factors and treatment outcomes were compared to identify clinical differences between oral SGC and SCC in total cases and in tumor size and subsite (propensity score)-matched pairs (N = 68 in each group). In addition, pattern of local invasion was pathologically assessed in a subset of SGC and SCC tumors.Results: Patients with SGC in the oral cavity showed >90% survival at 5 years. Most common pathologies of SGC were mucoepidermoid carcinoma (39.7%) and adenoid cystic carcinoma (35.3%), where high-grade tumors (including adenoid cystic carcinomas having solid components, grade 2 or 3) represented only 36.8%. Compared with oral SCC, surgery for SGC had narrow surgical safety margin. However, local control was very successful in SGC even with <5 mm or positive resection margin through surgery plus adjuvant radiation treatments or surgery alone for small low-grade tumors. Pathologic analysis revealed that the frequency of oral SGC with infiltrative tumor border was significantly lower than that of oral SCC (46.4 vs. 87.2%, P < 0.001).Conclusions: SGC in the oral cavity represents relatively good prognosis and has a locally less aggressive pathology compared with oral SCC. Adjuvant radiation can be very effective to control minimal residual disease in oral SGC. Our study proposed that a different treatment strategy for oral SGC would be reasonable in comparison with oral SCC.
Highlights
Oral cancer is the sixth most common cancer worldwide [1]
Regarding T and N status, there was a higher T tendency for oral salivary gland cancers (SGC) and higher N status for oral squamous cell carcinoma (SCC), which were similar to the previous report [23]
The percentage of M1 was higher in SGC group, mainly due to the adenoid cystic carcinoma pathology
Summary
Oral cancer is the sixth most common cancer worldwide [1]. While the most common malignant disease in the oral cavity is squamous cell carcinoma (SCC), other pathologic types of malignancy including salivary gland cancers (SGC) can occur in the oral cavity [1, 2]. SGC is relatively rare and comprises 1–6% of all head and neck cancers [3,4,5,6,7]. It has heterogeneous types of pathology with diverse tumor biology [4, 5, 8]. Concurrent chemoradiation is a standard treatment modality for high-risk oral SCC as a postoperative adjuvant treatment [9]. Adjuvant concurrent chemoradiation is not validated yet for high-risk SGC (currently under clinical trial) [10], and postoperative radiation is still a standard of care as an adjuvant treatment for SGC [11]. 5-year survival rate for patients with SCC ranges from 40 to 63% [2], while that for SGC is 71.8–90.1% and is characterized by late recurrence [6, 12, 13]
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