Radiation therapy in the management of Langerhans cell histiocytosis.

Twenty-two patients with Langerhans cell histiocytosis (LCH) were managed in the UCLA Department of Radiation Oncology from 1974 to 1987. Their median age was 17 years (range 1-42 years) and median followup 4.5 years (range 1-13 years). Fourteen patients had disease localized to a bone (13) or a soft tissue (one). Eight patients had LCH involving multiple bones (3) or soft tissues plus bones (5). Nine of 10 patients less than 19 years old had disease confined to bone(s) compared to 7 of 12 older patients. Fifty-six sites of LCH (40 bone, 16 soft tissue) were irradiated. Pediatric patients received therapy to 15 sites (14 bone, 1 soft tissue) and adults 41 sites (26 bone, 15 soft tissue). Median dose for bone lesions was 900 cGy (range 600-1,500) and for soft tissue 1,500 cGy (range 600-2,600). Local control was achieved in 46 of 56 sites (82%). Control rates for bone and soft tissue lesions were 35 of 40 (88%) and 11 of 16 (69%), respectively. Fifteen of 15 sites in pediatric patients were controlled compared to 29 of 41 (72%) in adults. Ten sites (18%) recurred 10 months to 4 years after irradiation. Recurrences were in-field and noted only in adults with involvement of multiple soft tissues plus bones. All recurrent soft tissue lesions had been treated with orthovoltage. Five patients developed new foci of LCH subsequent to irradiation. Four of these patients had disease involving soft tissues and bones. One patient with progressive LCH initially presented with a single bone lesion. The acute and chronic effects of radiation therapy were minimal. One patient suffered transient enlargement of adenopathy. An elevated serum TSH level was detected 9 years after irradiation of a cervical vertebra in another patient.