Langerhans cell histiocytosis (LCH) is a rare neoplastic disorder caused by somatic genetic alterations in hematopoietic precursor cells differentiating into CD1a+/CD207+ histiocytes. LCH clinical manifestation is highly heterogeneous. BRAF and MAP2K1 mutations account for approximately 80% of genetic driver alterations in neoplastic LCH-cells. However, their clinical associations remain incompletely understood. Here, we present an international clinicogenomic study of childhood LCH, investigating 377 patients genotyped for at least BRAFV600E. MAPK pathway gene alterations were detected in 300 (79.6%) patients, including 191 (50.7%) with BRAFV600E, 54 with MAP2K1 mutations, 39 with BRAF exon 12 mutations, 13 with rare BRAF alterations, and 3 with ARAF or KRAS mutations. Our results confirm that BRAFV600E associates with lower age at diagnosis and higher prevalence of multisystem LCH, high-risk disease, and skin involvement. Furthermore, BRAFV600E appeared to correlate with a higher prevalence of central nervous system (CNS)-risk bone lesions. In contrast, MAP2K1 mutations associated with a higher prevalence of SS-bone LCH, and BRAF exon 12 deletions seemed to correlate with more lung involvement. Although BRAFV600E correlated with reduced event-free survival (EFS) in the overall cohort, neither BRAF nor MAP2K1 mutations associated with EFS when patients were stratified by disease extent. Thus, the correlation of BRAFV600E with inferior clinical outcome is (primarily) driven by its association with disease extents known for high rates of progression or relapse, including multisystem LCH. These findings advance our understanding of factors underlying the remarkable clinical heterogeneity of LCH, but also question the independent prognostic value of lesional BRAFV600E status.
PURPOSE Patients with relapsed high-risk neuroblastoma (rHR-NB) have a poor prognosis. We hypothesized that graft-versus-neuroblastoma effects could be elicited by transplantation of haploidentical stem cells (haplo-SCT) exploiting cytotoxic functions of natural killer cells and their activation by the anti-GD2 antibody dinutuximab beta (DB). This phase I/II trial assessed safety, feasibility, and outcomes of immunotherapy with DB plus subcutaneous interleukin-2 (scIL2) after haplo-SCT in patients with rHR-NB. METHODS Patients age 1-21 years underwent T-/B-cell–depleted haplo-SCT followed by DB and scIL2. The primary end point ‘success of treatment’ encompassed patients receiving six cycles, being alive 180 days after end of trial treatment without progressive disease, unacceptable toxicity, acute graft-versus-host-disease (GvHD) ≥grade 3, or extensive chronic GvHD. RESULTS Seventy patients were screened, and 68 were eligible for immunotherapy. Median number of DB cycles was 6 (range, 1-9). Median number of scIL2 cycles was 3 (1−6). The primary end point was met by 37 patients (54.4%). Median observation time was 7.8 years. Five-year event-free survival (EFS) and overall survival from start of trial treatment were 43% (95% CI, 31 to 55) and 53% (95% CI, 41 to 65), respectively. Five-year EFS among patients in complete remission (CR; 52%; 95% CI, 31 to 69) or partial remission (44%; 95% CI, 27 to 60) before immunotherapy were significantly better compared with patients with nonresponse/mixed response/progressive disease (13%; 95% CI, 1 to 42; P = .026). Overall response rate in 43 patients with evidence of disease after haplo-SCT was 51% (22 patients), with 15 achieving CR (35%). Two patients developed GvHD grade 2 and 3 each. No unexpected adverse events occurred. CONCLUSION DB therapy after haplo-SCT in patients with rHR-NB is feasible, with low risk of inducing GvHD, and results in long-term remissions likely attributable to increased antineuroblastoma activity by donor-derived effector cells.
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