Challenging the Requirement to Treat the Contralateral Neck with >4-Mm Tumor Thickness in Patients Receiving Postoperative Radiation Therapy for Squamous Cell Carcinoma of the Oral Tongue or Floor of Mouth

Abstract

In patients with oral tongue or floor of mouth squamous cell carcinoma (SCC), the policy at our institution for many years has been to limit postoperative radiotherapy (RT) to the ipsilateral side when the primary tumor does not cross the midline, regardless of tumor thickness or depth of tumor invasion. We report the rate of contralateral neck failure in this group. We retrospectively reviewed the medical records of patients with T1-4 N1-N2b SCC of the oral tongue or floor of mouth who underwent postoperative RT to the primary site +/− ipsilateral neck RT between 1998 and 2014. No patients received radiation to the contralateral neck. All patients received resection of the primary site with or without ipsilateral and/or bilateral neck dissection. Our study population was 32 patients: 75% with close (<5 mm) or positive margins; 38% with perineural invasion. No patient had a tumor that crossed the midline. Tumor thickness was ≥4 mm in 75% of patients. Depth of invasion was >5 mm in 68% of patients. The rate of isolated contralateral neck recurrence was 3% (1/32). When delivering postoperative RT for oral tongue or floor of mouth cancer, the risk of not irradiating the contralateral neck is very low when the primary tumor does not cross the midline, regardless of other factors at the primary site, including tumor thickness and depth of invasion.