Assessment of Response to Treatment

Response assessment remains one of the most difficult areas in LCH therapy. It is easier when there is a specific area that can be monitored clinically or with ultrasonography, CT, PET, or MRI scans, such as the skin, hepato/splenomegaly, and other mass or lytic bone 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 are not particularly helpful in assessing the response of lytic bone lesions. Technetium Tc 99m bone scans remain positive in healing bone. PET scans may be helpful in monitoring the response to therapy because the intensity of the PET image diminishes with the response of lesions and healing of bone.[17]

For children or adults with lung LCH, pulmonary function testing and high-resolution CT scans are sensitive methods for detecting disease progression.[20] Residual interstitial changes reflecting residual fibrosis or residual inactive cysts must be distinguished from active disease; somatostatin analog scintigraphy may be useful in this regard.[162]