A comprehensive review of the DAL and Histiocyte Society clinical trials revealed a reactivation rate of 46% at 5 years for patients with multisystem LCH, with most reactivations occurring within 2 years of first remission. A second reactivation occurred in 44%, again within 2 years of the second remission. Involvement of the risk organs in these reactivations only occurred in those who were initially in the high-risk group (meaning they had liver, spleen, bone marrow, or lung involvement at the time of original diagnosis).[Level of evidence: 3iiiDiii] Most reactivations, even in patients with high-risk disease who initially responded to therapy, were in bone, skin, or other nonrisk locations.
The percentage of reactivations in multisystem disease was identical in the Japanese trial, [Level of evidence: 1iiA] and the LCH-II trial  (45% and 46%, respectively). There was not a statistically significant difference in reactivations between the high-risk and low-risk groups. Both the DAL-HX and Japanese studies concluded that intensified treatment increased rapid response, particularly in young children and infants younger than 2 years, and together with rapid switch to salvage therapy for nonresponders, reduced mortality for patients with high-risk multisystem LCH.
Treatment Options for Childhood LCH No Longer Considered Effective
Treatments for LCH in any location which have been used in the past but are no longer recommended include cyclosporine  and interferon-alpha. Extensive surgery is also not indicated. Curettage of a circumscribed skull lesion may be sufficient if the lesion in not in the temporal, mastoid, or orbital areas (CNS-risk). Patients with disease in these particular sites are recommended to receive 6 months of systemic therapy with vinblastine and prednisone. For lesions of the mandible, extensive surgery may destroy any possibility of secondary tooth development. Surgical resection of groin or genital lesions is contraindicated as these lesions can be healed by chemotherapy.
Radiation therapy use in LCH has been significantly reduced in pediatric patients, and even low-dose radiation therapy should be limited to single-bone vertebral body lesions or other single-bone lesions compressing the spinal cord or optic nerve that do not respond to chemotherapy.
Assessment of Response to Treatment
Response assessment remains one of the most difficult areas in LCH therapy unless there is a specific area that can be followed clinically or with sonography, CT, or MRI scans of areas such as the skin, hepato/splenomegaly, and other mass lesions. Clinical judgment including evaluation of pain and other symptoms remains important.
Bone lesions may take many months to heal and are difficult to evaluate on plain radiographs, although sclerosis around the periphery of a bone lesion suggests healing. CT or MRI scans are useful in assessing response of a soft tissue mass associated with a bone lesion, but is not particularly helpful in an isolated lytic bone lesion. Technetium bone scans remain positive in healing bone. PET scans may be helpful in following the response to therapy since intensity of the PET image diminishes with healing of a bone or other lesion.