Long-Term Outcomes Following Radiotherapy for Pediatric Salivary Gland Tumors

Abstract

Objective

In contrast to adult salivary gland tumors, our institutional guidelines in children utilize lower radiation doses, smaller target margins, and proton therapy (PT) to minimize radiation to the developing skull base anatomy. We also do not routinely recommend prophylactic nodal irradiation or elective neck dissection. Herein we report the outcomes of our age-based management approach.

Methods

We conducted a retrospective review of thirty-one consecutive pediatric patients (ages 6-21) with salivary gland tumors treated with PT at our institution between 2006-2023. The most common histologies were mucoepidermoid carcinoma (n=14), acinic cell carcinoma (n=5), and adenoid cystic carcinoma (n=5). Eight patients with radiographic lymphadenopathy underwent neck dissection prior to presentation, with selective dissections involving < 4 nodal levels in 7/8 cases. The gross tumor volume (GTV) encompassed the residual tumor and tumor bed. Clinical target volume (CTV1), defined as GTV plus a 1 cm, received a dose of 50.4Gy. Prophylactic nodal irradiation was administered to only three patients as part of CTV1. CTV2 equaled the GTV and was treated to a median total dose of 64.8Gy (range, 61.2-70.8Gy). Toxicity data were graded using Common Terminology Criteria for Adverse Events Version 4.0.

Results

The median follow-up was 7.5 years (range, 1.2-15 years). Overall survival was 96% and local control was 94%. There were no nodal recurrences. Acute toxicities were limited to mucositis requiring opioids and transient grade 3 dermatitis. The most serious late toxicity involved the auditory system including 4 patients requiring hearing aids, 1 with chronic otitis media, 1 with osteonecrosis of the mastoid, and 1 with external canal stenosis. There was no grade 4 toxicity nor second malignancy.

Conclusion

Conservative neck management and moderate-dose PT delivered to small volumes resulted in excellent long-term disease control and limited toxicity in children with common salivary gland tumors.