RADIATION-INDUCED MALIGNANT FIBROUS HISTIOCYTOMA IN PATIENTS WITH NASOPHARYNGEAL CARCINOMA

Objective: To evaluate the prevalence, 15-year cumulative incidence, t ime interval, and prognosis of radiation-induced malignant fibrous his tiocytoma of the head and neck in long-term survivors of nasopharyngea l carcinoma. Design: Cohort. Setting: Tertiary care hospital. Patients : Eight long-term survivors of nasopharyngeal carcinoma with malignant fibrous histiocytoma in the maxillary sinus or nasal cavity. Main Out come Measurement: Survival of postirradiation malignant fibrous histio cytoma in patients with nasopharyngeal carcinoma. Results: The prevale nce of radiation-induced malignant fibrous histiocytoma in long-term s urvivors of nasopharyngeal carcinoma was 0.38%. The 15-year cumulative incidence was 2.2%. Most tumors occurred in the maxillary sinus and w ere characterized by spindle-shaped tumor cells with plump nuclei arra nged in a whorl or storiform pattern in a fibrous stroma. The mean int erval between malignant fibrous histiocytoma and nasopharyngeal carcin oma was 121 months. Local recurrence developed in all cases within 9 m onths after surgery. Six patients died of disease without distant meta stasis within 30 months. Two patients were alive with disease for 10 a nd 32 months, respectively. Conclusion: Radiation-induced malignant fi brous histiocytoma in the head and neck region in long-term survivors of nasopharyngeal carcinoma is rare. It takes a long time to occur aft er irradiation and is locally invasive with poor prognosis.