Background: Parotid squamous cell carcinoma (SCC) is an uncommon entity among salivary gland tumors. Primary SCC of the parotid gland is a diagnosis of exclusion and exceedingly rare; metastatic SCC of the parotid gland from cutaneous malignancies is far more common. Historically, the literature surrounding SCC of the parotid has been limited to single institution studies. However, with the advent of cancer databases, population based data is becoming more available and robust. The objectives of this study were to examine survival outcomes based on treatment and prognostic factors related to survival for primary squamous cell carcinoma of the parotid gland.
Study design: Retrospective study of the Surveillance, Epidemiology, and End Results (SEER) registry.
Methods: We performed a retrospective review on survival outcomes related to squamous cell carcinoma of the parotid gland using the Surveillance, Epidemiology, and End Results Program (SEER). Data regarding patient demographics, tumor characteristics, and treatment was obtained. Univariate Kaplan-Meier and multivariate Cox survival analyses were performed using variables including grouped age, gender, grade, TNM stage, overall stage. Treatment groups used in the analysis included surgery, surgery with postoperative radiation, surgery with postoperative chemotherapy and radiation, and surgery with postoperative chemotherapy.
Results: 3320 patients met inclusionary criteria based on tumor site of the parotid gland and histological diagnosis of squamous cell carcinoma. Mean overall survival was 2.3 years. Apart from histologic grade, all other variables including age, TNM stage, overall stage, and all treatment groups were found to have a statistically significant effect on survival (p<0.05). On multivariate analysis (Table 1), advanced age (60+), stage, and female gender were independently shown to decrease survival. Surgery with adjuvant radiation (HR 0.594, CI [0.535-0.659]) and surgery with adjuvant chemotherapy and radiation (HR 0.667, CI [0.561-0.792] were independently shown to increase survival.
Conclusion: This study highlights prognostic factors for survival in squamous cell carcinoma of the parotid gland including age, overall stage, TNM staging, and conventional treatment modalities. Surgery remains the gold standard in the treatment of this malignancy and the literature largely supports the use of adjuvant radiation particularly in advanced stage or in a high-risk subset of patients. Our analysis demonstrates improvement in survival outcomes with not only radiation after surgery but also the addition of chemotherapy to adjuvant radiation therapy postoperatively. This underscores the necessity for further investigation into the role of postoperative chemoradiation therapy in the treatment of parotid squamous cell carcinoma.
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