Definitive Chemoradiotherapy for Salivary Gland Cancers

Abstract

Surgical resection is the standard of care for salivary gland tumors of the head and neck. The role of radiotherapy is typically reserved for the adjuvant setting in those patients with high risk factors on surgical pathology. Surgical resection in some cases may lead to significant impairment in speech or swallowing due to location of the primary tumor. In other cases, patients may not be medically able to receive an oncologic resection. Our institution has developed a protocol for organ preservation for well-selected salivary gland malignancies. Here we report disease outcomes of salivary gland cancer patients treated with definitive chemoradiotherapy. We retrospectively reviewed all salivary gland cancer patients at our institution who received definitive chemoradiation from January 1990 to December 2019. Chemoradiation typically consisted of 4 to 6 alternating weekly cycles of paclitaxel (100 mg/m2 on d1), infusion 5-fluorouracil (600 mg/m2/d on d0-5), hydroxyurea (500 mg PO BID), and either 1.8 Gy or 2 Gy daily or 1.5 Gy twice-daily irradiation followed by a 9-day treatment break (TFHX). The Kaplan-Meier method was used to estimate rates of locoregional control (LRC), distant metastasis-free survival (DMFS), and overall survival (OS). Nineteen patients met eligibility criteria and were included for analysis. 53% of patients had adenoid cystic histology. Salivary duct, mucoepidermoid, acinic cell, and myoepithelial histologies each were represented by 10.5% of patients. About 26% of tumors were located in the nasopharynx, 21% in the base of tongue and 26% in the parotid. 74% of the patients were node negative and 53% of patients had stage IVA disease. T3 disease occurred in 26.3% while T4a and T4b disease occurred in 31.6% each. Median follow-up was 45.8 (IQR: 29-66) months. 47% of patients were treated using a twice daily approach, while 53% were treated with daily fractionation with a median dose of 72 Gy (IQR: 70-75). Three-year locoregional control (LRC), distant-metastasis free survival (DMFS), and overall survival (OS) were 93%, 76%, and 81% respectively. Eight of nine distant failures had T4a/T4b disease. Accounting for competing risk of death, local failure was 5.6% at three years. The most common acute complications were grade 2-3 mucositis (74%) and skin toxicity (47%). One patient discontinued chemoradiation due to severe hand foot mouth syndrome. 42% of patients had late toxicity of xerostomia. Promising organ preservation is seen with concurrent chemoradiation for salivary gland cancer patients. Further prospective study of organ preservation in salivary gland cancers is warranted.