Phase II study of polymyxin B, tobramycin, and clotrimazole to prevent oral irradiation mucositis

Colonization of the oral mucosa by gram-negative organisms and/or fungi is theorized to be an etiologic factor in severe mucosal reactions in patients receiving radiation to treat head and neck cancers. Patients treated with altered fractionation schedules have high rates of confluent mucositis, which can be slow to heal and can on occasion disrupt the continuity of the radiation course, with possible detrimental effects on outcome. It has been proposed that antimicrobial agents directed at these organisms can alleviate the severity of the mucosal reactions. We studied the use of a suspension of polymyxin B and tobramycin in conjunction with a clotrimazole troche in patients receiving radiotherapy with altered fractionation schedules to the oropharynx or oral cavity. Thirty-seven patients were enrolled in the trial. Radiation doses ranged from 63 to 77 Gy over 5-7 weeks. The rate of confluent mucositis in the entire group was 84%. This was not significantly different (P > 0.1) from a rate of 85% seen in an historical control group of 79 patients treated with our concomitant boost regimen. Possible reasons for the apparent ineffectiveness of this antibacterial-antifungal regimen are discussed.