Bone Abstracts

Introduction: Langerhans cell histiocytosis (LCH) is a monoclonal disorder characterized by proliferation and accumulation of atypical Langerhans cells. Bone involvement is particularly destructive and to date, no standard of care exists. Bisphosphonates are osteoclast inhibitors that could target the multinucleated giant cells within the LCH lesions and might be used to alleviate bone pain and the progression of disease.

Objective: To evaluate the efficacy and safety of bisphosphonates in treating bone LCH and extra-osseous disease.

Methods: An international, multicenter, retrospective study was conducted in children and adults with LCH who received bisphosphonates between 1995 and 2014.

Results: Eighteen patients with single-system or multi-system LCH were identified from 4 centers. All received bisphosphonates therapy either at diagnosis or at ≥1st reactivation. Median age at start of bisphosphonates was 23.7 years (range 5.7–38.3), and median follow-up time post bisphosphonate therapy was 2.8 years (range 0.9–5.0). The majority of patients received zoledronate (n=10), followed by pamidronate (n=4) and alendronate (n=3); one patient received both pamidronate and zoledronate. All patients reported significant reduction in pain, to either no or mild pain after administration of bisphosphonates. Thirteen of 18 patients (72%) achieved complete remission (CR) in the bone lesions, including lesions in skin (n=1), lung (n=1) and pituitary (n=1); two had partial response and three had no response. Among the 13 CR patients, 12 had no active disease for a median of 4.1 years (range 2.8–5.1) and one developed radiographic neurodegeneration after 2 years. Bisphosphonates were well tolerated. Progression-free survival (PFS) was 75±11% at 3 years, with a trend favoring better PFS (P=0.24) in patients with no or first reactivation compared with the rest.

Conclusion: Bisphosphonates are well-tolerated medications that can significantly improve bone pain in patients with osseous LCH lesions, and may be effective in treating extra-osseous disease.