Survival in primary hemophagocytic lymphohistiocytosis 2016-2021: etoposide is better than its reputation
Abstract
Primary hemophagocytic lymphohistiocytosis (pHLH) is a life-threatening hyperinflammatory syndrome that develops mainly in patients with genetic disorders of lymphocyte cytotoxicity and X-linked lymphoproliferative syndromes. Previous studies with etoposide-based treatment followed by hematopoetic stem cell transplantation (HSCT) resulted in 50-59% 5-year survival.
Contemporary data are lacking. We evaluated 88 pHLH patients documented in the international HLH Registry between 2016-2021 with follow-up until 6/2023.
In 12/88 patients, the diagnosis was made without HLH activity, based on index siblings or partial albinism. Major HLH-directed drugs (etoposide, ATG, alemtuzumab, emapalumab, ruxolitinib) were given to 66/76 symptomatic patients (86% first-line etoposide); 16/57 etoposide-treated and 3/9 patients with other first-line treatment received salvage therapy.
HSCT was performed in 75 patients, 7 symptomatic patients died before HSCT. 3-year probability of survival (pSU) was 82% (CI 72%-88%) for the entire cohort and 77% (CI 64-86%) for symptomatic patients receiving first-line etoposide. Compared to the HLH-2004 study, both pre-HSCT survival (83% to 91%) and post-HSCT survival of patients receiving first-line etoposide improved (70% to 88%).
Differences to HLH-2004 included preferential use of reduced-toxicity conditioning and reduced time from diagnosis to HSCT (148 to 88 days). 3-year pSU was lower with haploidentical (44%, 4/9 patients) than with other types of donors (94%, 4/66, p<0.001). Importantly, also in this study, early HSCT of asymptomatic patients resulted in excellent survival (100%), emphasizing the potential benefit of newborn screening.
This contemporary standard-of-care study of pHLH patients reveals that first-line etoposide-based therapy is better than previously reported, providing a benchmark for novel treatment regimes.