Long-term outcomes after external beam irradiation and brachytherapy boost for base-of-tongue cancers

Purpose: To assess long-term efficacy and toxicity associated with external beam irradiation (EBRT) and interstitial ¹⁹²Ir implantation for the treatment of squamous carcinoma of the base of tongue. Methods and Materials: Between April 1975 and December 1993, 41 patients with base-of-tongue carcinomas were treated with ¹⁹²Ir interstitial implants after EBRT at Stanford University. One patient had Stage I, 6 had Stage II, 7 had Stage III, and 27 had Stage IV tumors. Twenty-eight patients had cervical lymph node involvement at diagnosis. All received EBRT to a median dose of 50 Gy (range 48.9-68 Gy) to the primary tumor and regional lymph nodes before brachytherapy. Interstitial implant was performed 2-4 weeks after EBRT. Intraoperatively, nylon catheters were placed via steel trocars into the base of tongue, glossotonsillar groove, and pharyngo-epiglottic fold using a catheter looping technique. Twenty-three of 28 node-positive patients also underwent simultaneous neck dissections. Postoperatively, the ¹⁹²Ir seeds were inserted and allowed to remain in place for approximately 35 h to achieve a median tumor dose of 26 Gy (range 20-34 Gy) to a median volume of 73 cc. Survival, local control, and complications were assessed. Results: With a median follow-up of 62 months (range 9-215) for all patients and 90 months for alive patients, the 5-year Kaplan-Meier survival estimate was 66%. The 5-year local control rate was 82%, with 7 patients recurring locally, 2 of whom were salvaged with surgery. Nodal control was achieved in 93% of patients with either EBRT alone or in combination with neck dissection. The 5-year freedom from distant metastasis rate was 83%. Acute complications included transient bleeding (5%) and infection (8%). Late complication included soft-tissue necrosis/ulceration (7%), osteoradionecrosis (5%), and xerostomia. Conclusion: Base-of-tongue carcinoma can be effectively treated with EBRT and ¹⁹²Ir implant boost. Local control is excellent and complication rates are acceptable.