Histiocytosis X: does radiotherapy still have a role?

Seventeen cases of histiocytosis X are presented (11 children and 6 young adults, with the usual male predominance), having a minimum follow-up of 1 year and a maximum of 20 years. In these age groups, even small doses of radiation should not be given without careful consideration, but fairly low doses carry only a small risk and may be very useful in management. Unlike chemotherapy, radiotherapy can be confined to the affected area, or to the area causing symptoms. All but two of our patients had radiotherapy for bone deposits; only one failed to show a complete response. In addition, the diabetes insipidus of two children responded immediately to radiation of the pituitary. One patient, however, after responding well to radiation for bone deposits, suffered increasing symptoms due to lung involvement and the latter showed no response. This striking contrast in radiosensitivity is hard to explain, given the identical histology obtained by biopsy from each site, but it has been noted many times by others.