BASE-OF-TONGUE CARCINOMA - TREATMENT RESULTS USING CONCOMITANT BOOST RADIOTHERAPY

Purpose: To evaluate the efficacy of accelerated fractionated radiothe rapy using the concomitant boost schedule for patients with squamous c ell carcinoma of the base of tongue. Methods and Materials: Between Se ptember 1984 and July 1992, 54 patients with squamous carcinoma of the base of tongue were treated at The University of Texas M. D. Anderson Cancer Center using the concomitant boost schedule. The distribution of T and N stages was T1-4, T2-27, T3-22, and T4-1; N0-9, N1-11, N2-24 , N3-7, and NX-3. American Joint Committee on Cancer (AJCC) stage grou pings were II-6, III-14, and IV-34. Before radiation, nodal excision a nd neck dissection were done in 5 and 10 patients, respectively; 5 pat ients had neck dissections after radiotherapy. Standard on and off spi nal cord fields were irradiated with 1.8 Gy fractions to 54 Gy given o ver 6 weeks. The boost was given concomitantly during the large field treatment as a second daily (1.5 Gy) fraction, with an interfraction i nterval of 4-6 h. The median dose to the primary tumor was 72 Gy (rang e, 66-74 Gy). The median treatment duration was 42 days (range, 39-48 days). Only three patients had treatment interrupted for more than one scheduled treatment day. Results: The 5-year actuarial overall surviv al and disease-specific survival rates were 59 and 65%, respectively, with a median follow-up of 41 months. The 5-year actuarial locoregiona l control rate was 76%. The actuarial local control rates achieved wit h radiotherapy at 5 years for T1, T2, and T3 primary tumors were 100%, 96%, and 67%, respectively; including surgical salvage, the local con trol rate of T3 primary tumors was 70%. Six patients had regional fail ures, which in three patients occurred in conjunction with primary tum or recurrence. Twenty-six patients with regional adenopathy were treat ed with radiation alone to full dose and had a complete clinical respo nse in the neck; no planned neck dissections were performed in these p atients. Only 2 of these 26 patients had subsequent regional failures. The 5-year actuarial risk of distant metastases in patients whose dis ease was controlled locoregionally was 21%. Grade 3 or 4 confluent acu te mucositis occurred in 94% of patients. However, late complications were Limited to two cases of transient mandibular exposure and three c ases of self-limited mucosal ulcerations. Conclusion: The concomitant boost fractionation schedule is a very effective regimen for this dise ase when appropriately selected patients are treated with meticulous t echnique. The therapeutic ratio is favorable, with a high rate of dise ase control and no persistent severe late complications. Patients whos e neck disease responds completely to treatment with this schedule do not appear to need a planned neck dissection.