This protocol applies to patients with mucocutaneous Langerhans cell histiocytosis whose disease did not adequately respond to a prior line of local treatment. When cutaneous lesions persist despite local measures, a structured escalation is required.
The previous treatment line consisted of local therapy directed at refractory cutaneous disease, using agents such as imiquimod, 20% nitrogen mustard, or irradiation. Response was defined as any degree of improvement in cutaneous lesions on skin examination. Failure to reach this threshold is the escalation criterion that brings the patient to this next-line protocol.
After local therapy failure, the recommended strategy moves to systemic chemotherapy. Multiple chemotherapy options are recognised in this setting — the specific agents, their relative preference, and the selection rationale are laid out in the full protocol.
The therapeutic aim is any degree of improvement in clinical or radiographic findings. For patients with abnormal FDG-PET/CT findings at diagnosis, response is first assessed at approximately 2–3 months after therapy initiation.
DOI: 10.1182/blood.2021014343
For multisystem LCH or extensive/refractory multifocal single-system LCH, systemic chemotherapy agents such as cladribine, cytarabine, or vinblastine ± prednisone are recommended.
Among systemic treatment options for LCH, chemotherapy using either cladribine or cytarabine is preferred because of relatively high overall response rates and the potential for long-term remissions with limited cycles of treatment.
Vinblastine ± prednisone is a reasonable alternative, although it is not the preferred choice of therapy in adults given the high risk of relapse and potential for peripheral neuropathy.
Any degree of improvement in clinical or radiographic findings is considered a response.
For patients with abnormal FDG-PET/CT findings at diagnosis, the first response assessment should occur in 2 to 3 months of initiation of therapy and every 3 to 6 months thereafter.
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