Proton beam therapy for inoperable recurrence of bronchial high-grade mucoepidermoid carcinoma

We report the case of a 17-year-old patient who received four courses of proton beam therapy for inoperable recurrent high-grade bronchial mucoepidermoid carcinoma of the chest wall and lymph nodes. The equivalent doses in conventional fractionation of 79.2-80.6 Gy were applied to the tumor from the first to third courses of proton beam therapy; the hemi-chest wall was also irradiated prophylactically in the third course. The irradiated tumor recurred marginally and liver metastasis developed, but tumor size within the irradiated field was suppressed. Proton beam therapy was also applied to the marginally recurrent tumor in the fourth course. The patient died of cancer about 5 years after the first course of proton beam therapy-about 9 years after the initial diagnosis and surgery. Repeated irradiation of the mediastinum and chest wall with photon radiotherapy is often limited by side-effects in the heart, esophagus and spinal cord. However, no severe late complications in critical organs were detected in this case. Only a Grade 2 skin reaction and lymphatic edema were observed. Therefore, high-dose proton beam therapy may be an option as a salvage therapy with less toxicity to normal tissues compared with photon radiotherapy and provide an alternative to repeated surgery.