Hemophagocytic lymphohistiocytosis (HLH) comprises familial (primary) hemophagocytic lymphohistiocytosis (FHL) and secondary HLH (SHLH), both clinically characterized by fever, hepatosplenomegaly, and cytopenia. FHL, an autosomal recessive disease invariably fatal when untreated, is associated with defective triggering of apoptosis and reduced cytotoxic activity, resulting in a widespread accumulation of T lymphocytes and activated macrophages. In 1994 the Histiocyte Society initiated a prospective international collaborative therapeutic study (HLH-94), aiming at improved survival. It combined chemotherapy and immunotherapy (etoposide, corticosteroids, cyclosporin A, and, in selected patients, intrathecal methotrexate), followed by bone marrow transplantation (BMT) in persistent, recurring, and/or familial disease. Between July 1, 1994, and June 30, 1998, 113 eligible patients aged no more than 15 years from 21 countries started HLH-94. All had either an affected sibling (n = 25) and/or fulfilled the Histiocyte Society diagnostic criteria. At a median follow-up of 3.1 years, the estimated 3-year probability of survival overall was 55% (95% confidence interval ± 9%), and in the familial cases, 51% (± 20%). Twenty enrolled children were alive and off therapy for more than 12 months without BMT. For patients who received transplants (n = 65), died prior to BMT (n = 25), or were still on therapy (n = 3), the 3-year survival was 45% (± 10%). The 3-year probability of survival after BMT was 62% (± 12%). HLH-94 is very effective, allowing BMT in most patients. Survival of children with HLH has been greatly improved.

The Associazione Italiana di Ematologia Oncologia Pediatrica and the Berlin-Frankfurt-Münster Acute Lymphoblastic Leukemia (AIEOP-BFM ALL 2000) study has for the first time introduced standardized quantitative assessment of minimal residual disease (MRD) based on immunoglobulin and T-cell receptor gene rearrangements as polymerase chain reaction targets (PCR-MRD), at 2 time points (TPs), to stratify patients in a large prospective study. Patients with precursor B (pB) ALL (n = 3184) were considered MRD standard risk (MRD-SR) if MRD was already negative at day 33 (analyzed by 2 markers, with a sensitivity of at least 10⁻⁴); MRD high risk (MRD-HR) if 10⁻³ or more at day 78 and MRD intermediate risk (MRD-IR): others. MRD-SR patients were 42% (1348): 5-year event-free survival (EFS, standard error) is 92.3% (0.9). Fifty-two percent (1647) were MRD-IR: EFS 77.6% (1.3). Six percent of patients (189) were MRD-HR: EFS 50.1% (4.1; P < .001). PCR-MRD discriminated prognosis even on top of white blood cell count, age, early response to prednisone, and genotype. MRD response detected by sensitive quantitative PCR at 2 predefined TPs is highly predictive for relapse in childhood pB-ALL. The study is registered at http://clinicaltrials.gov: NCT00430118 for BFM and NCT00613457 for AIEOP.

Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening hyperinflammatory syndrome comprising familial/genetic HLH (FHL) and secondary HLH. In the HLH-94 study, with an estimated 5-year probability of survival (pSu) of 54% (95% CI, 48-60%), systemic therapy included etoposide, dexamethasone and, from week nine, cyclosporine A (CSA). HSCT was indicated in patients with familial/genetic, relapsing, or severe and persistent disease. In HLH-2004, CSA was instead administered upfront, aiming to reduce pre-HSCT mortality and morbidity. During 2004-2011, 369 children aged <18-years fulfilled the HLH-2004 inclusion criteria (5/8 diagnostic criteria, affected siblings, and/or molecular diagnosis in FHL-causative genes). At a median follow-up of 5.2 years, 230/369 (62%) patients were alive (5-year pSu 61%, 56-67%). The 5-year pSu in children with (n=168) and without (n=201) family history/genetically verified FHL was 59% (52-67%) and 64% (57-71%), respectively [familial occurrence (n=47): 58% (45-75%)]. Comparing with historical data (HLH-94), using HLH-94 inclusion criteria, pre-HSCT mortality was non-significantly reduced from 27% to 19% (P=.064 adjusted for age and gender). Time from start of therapy to HSCT was shorter compared to HLH-94 (P=.020 adjusted for age and gender) and reported neurological alterations at HSCT were 22% in HLH-94 and 17% in HLH-2004 (using HLH-94 inclusion criteria). Five-year pSu post-HSCT overall was 66% [verified FHL 70% (63-78%)]. Additional analyses provided specific suggestions on potential pre-HSCT treatment improvements. HLH-2004 confirms that a majority of patients may be rescued by the etoposide/dexamethasone combination but intensification with CSA upfront, adding corticosteroids to intrathecal therapy, and reduced time to HSCT did not improve outcome significantly. Key points Early introduction of cyclosporine did not improve HLH outcome in patients treated with the HLH-94 etoposide-dexamethasone backbone (P=.06) HLH-2004 may possibly be improved by risk group stratification, less therapy reduction weeks 7-8 for verified FHL patients, and earlier HSCT

Hemophagocytic lymphohistiocytosis (HLH) used to have a dismal prognosis. We report the final results of HLH-94, the largest prospective diagnostic/therapeutic HLH study so far. The treatment includes immunosuppressive and cytotoxic therapy aiming at clinical remission, followed by HSCT in patients with familial, persistent, or recurrent disease. Altogether, 249 patients fulfilled inclusion criteria and started HLH-94 therapy (July 1994-December 2003); 227 (91%) were followed-up for ≥ 5 years. At 6.2 years median follow-up, estimated 5-year probability of survival was 54% ± 6%. Seventy-two patients (29%) died before HSCT, 64 within 1 year, 97% of whom had active disease. In 124 patients who underwent HSCT, 5-year survival was 66 ± 8%; tendency to increased survival (P = .064) in patients with nonactive disease at HSCT. Patients with familial disease had a 5-year survival of 50% ± 13%; none survived without HSCT. Patients deceased during the first 2 months more often had jaundice, edema, and elevated creatinine. Forty-nine patients (20%) were alive without signs of HLH activity and off-therapy > 1-year without HSCT; they presented at older age (P < .001), were more often female (P = .011), and less often had CNS disease (P < .001) or hepatomegaly (P = .007). To conclude, HLH-94 chemoimmunotherapy has considerably improved outcome in HLH. Collaborative efforts are needed to further reduce early mortality, HSCT-related mortality, and neurologic late effects.