Stem cell transplantation for children with hemophagocytic lymphohistiocytosis: results from the HLH-2004 studyWe report the largest prospective study thus far on hematopoietic stem cell transplantation (HSCT) in hemophagocytic lymphohistiocytosis (HLH), a life-threatening hyperinflammatory syndrome comprising familial/genetic HLH (FHL) and secondary HLH. Although all patients with HLH typically need intensive anti-inflammatory therapy, patients with FHL also need HSCT to be cured. In the international HLH-2004 study, 187 children aged <18 years fulfilling the study inclusion criteria (5 of 8 diagnostic criteria, affected sibling, or molecular diagnosis in FHL-causative genes) underwent 209 transplants (2004-2012), defined as indicated in patients with familial/genetic, relapsing, or severe/persistent disease. Five-year overall survival (OS) post-HSCT was 66% (95% confidence interval [CI], 59-72); event-free survival (EFS) was 60% (95% CI, 52-67). Five-year OS was 81% (95% CI, 65-90) for children with a complete response and 59% (95% CI, 48-69) for those with a partial response (hazard ratio [HR], 2.12; 95% CI, 1.06-4.27; P = .035). For children with verified FHL (family history/genetically verified, n = 134), 5-year OS was 71% (95% CI, 62-78) and EFS was 62% (95% CI, 54-70); 5-year OS for children without verified FHL (n = 53) was significantly lower (52%; 95% CI, 38-65) (P = .040; HR, 1.69; 95% CI, 1.03-2.77); they were also significantly older. Notably, 20 (38%) of 53 patients without verified FHL had natural killer cell activity reported as normal at diagnosis, after 2 months, or at HSCT, suggestive of secondary HLH; and in addition 14 (26%) of these 53 children had no evidence of biallelic mutations despite having 3 or 4 FHL genes analyzed (natural killer cell activity not analyzed after 2 months or at HSCT). We conclude that post-HSCT survival in FHL remains suboptimal, and that the FHL diagnosis should be carefully investigated before HSCT. Pretransplant complete remission is beneficial but not mandatory to achieve post-HSCT survival. This trial was registered at www.clinicaltrials.gov as #NCT00426101.
Assessment of intrathecal therapy in the treatment of familial haemophagocytic lymphohistiocytosisHaemophagocytic lymphohistiocytosis (HLH), characterized by uncontrolled hyperinflammation and usually rapidly fatal in infants if not treated, is classified as primary (genetic, Mendelian), including the most common form, familial haemophagocytic lymphohistiocytosis (FHL) or secondary (acquired, non-Mendelian).1-3 Typical manifestations include fever, cytopenias, hepatosplenomegaly, liver dysfunction, hyperferritinaemia, hypertriglyceridaemia and hypofibrinogenaemia.4, 5 Additionally, central nervous system (CNS) involvement with cerebrospinal fluid (CSF) and/or neurological abnormalities, including irritability, meningismus, seizures, ataxia and delayed psychomotor development, affects most FHL patients already at diagnosis.6-10 Moreover, neurological sequelae are the main cause of late morbidity.5 The treatment protocols HLH-94 and HLH-2004 are based on etoposide, dexamethasone and ciclosporin (CSA), followed by definitive cure through haematopoietic stem cell transplantation (HSCT).4, 5, 11-13 In patients with progressive neurological symptoms during the first 2 weeks or if an abnormal CSF at onset has not improved after 2 weeks, additional intrathecal (IT) methotrexate, and in HLH-2004 also IT prednisolone, is recommended.4, 11 Despite its long-standing use, the efficacy of IT therapy in HLH has never been formally evaluated. Therefore, although the HLH-2004 study (the largest study on FHL globally so far) was not designed to evaluate the efficacy of IT therapy, we performed a post hoc retrospective analysis focusing on the course of neurological symptoms in FHL patients treated with and without IT therapy. Altogether, 368 patients in the HLH-2004 database met the HLH-2004 inclusion criteria, that is, were < 18 years old and either fulfilled ≥5 of eight diagnostic criteria, had an affected sibling and/or a molecular diagnosis consistent with FHL, and, additionally, had no prior cytotoxic or CSA treatment and no other underlying disease.13 Among these 368 patients, 165 had FHL confirmed by an affected sibling and/or biallelic mutations in FHL-causing genes (after excluding two patients with biallelic PRF1 p.Ala91Val variants which are considered a polymorphism) (Figure 1).14 Of these 165, 110 were alive after 2 months of therapy without having undergone HSCT and had data on IT treatment during this period. Patients with missing data on neurological symptoms and/or CSF abnormalities at onset (n = 22) were excluded, as well as patients with neither neurological symptoms nor CSF abnormalities at onset (n = 10). The final study group included 78 patients with confirmed CNS involvement at the onset of HLH-2004 treatment, characterized by neurological alterations (n = 42) and/or CSF abnormalities (n = 61), from 17 countries (Figure 1). Patients who received IT treatment (‘IT group’; n = 37) were compared with those who did not (‘non-IT group’; n = 41). A subgroup analysis was conducted on patients with neurological alterations at onset, comparing those who received IT treatment to those who did not. The HLH-2004 study (Supporting Information Text, Figure S1) was approved by the Ethics Committee of the Karolinska Institute (2004-219/3) and registered at clinicaltrials.gov, identifier: NCT00426101. Informed consent was obtained. HLH disease activity and CNS involvement were assessed using case report forms, defined before the study and completed prospectively at each hospital at predefined reporting times (Supporting Information Text, Table S1). The two-tailed Fisher's exact test was used for categorical variables to compare the characteristics, disease activity and outcomes of patients who received versus those who did not receive IT treatment, using SPSS (IBM SPSS Statistics for Macintosh, version 29.0.1.0, IBM Corp, Armonk, NY, USA). p-values below 0.05 were considered statistically significant. There were no significant differences in visceral disease activity at onset, neither between the entire IT and non-IT groups nor between the two corresponding subgroups with neurological symptoms at onset (Table 1). In the IT group, 22/37 (59%) were aged <1 year at onset (median 217 days, IQR 87–534) compared to 33/41 (80%) in the non-IT group (median 102 days, IQR 70–303). See Table S2 for reported mutations in both groups. At the start of HLH-2004 treatment, 42/78 patients (54%) exhibited neurological alterations and 61/67 (91%, no data [nd] = 11) had abnormal CSF, with 36 patients showing only abnormal CSF (Figure 1). In the IT group, 23/37 (62%) had neurological alterations at onset, including eight with psychomotor retardation. In the non-IT group, 19/41 (46%) had neurological alterations, including four with psychomotor retardation (Table S1). The number of patients with abnormal magnetic resonance imaging (MRI) differed between the IT and non-IT groups (IT = 15 [63%] and non-IT = 8 [31%]; p = 0.046) (Table 1). However, there was no difference between the groups regarding the distribution of patients with normal versus restricted functional activity at onset (Table 1). Three children, in addition to the 78 evaluated, had neuroradiological alterations as their only CNS manifestation. All were asymptomatic, both at onset and after 2 months. More patients in the IT group (17/34 [50%], nd = 3) had neurological alterations at 2 months compared to the non-IT group (10/40 [25%], nd = 1) (p = 0.032) (Table S3). Rates of neurological normalization and development did not significantly differ between the groups with available follow-up data. Improvement from neurological symptoms at onset to no symptoms at 2 months occurred in 8/21 IT patients (38%) and 11/18 (61%) non-IT patients (p = 0.20) (Figure 1). Of asymptomatic patients at onset, 4/13 (31%) IT patients compared to 3/22 (14%) non-IT patients developed neurological symptoms within 2 months (p = 0.38) (Figure 1). Furthermore, neurological outcomes did not differ between IT patients and non-IT patients with abnormal, normal or missing CSF at onset (Table S4). At 2 months, psychomotor retardation was reported in 7/34 IT patients (21%) and 9/40 (23%) non-IT patients. Among patients with no psychomotor retardation at onset, 4/27 (15%) IT and 6/36 (17%) non-IT patients developed it within 2 months (p = 1.0) (Figure 1). Regarding patient functional activity, 11/35 IT patients (31%, nd = 2) were considered to have normal activity status at 2 months compared to 19/37 non-IT patients (51%, nd = 4). There was no significant difference in the proportion of patients with normal and abnormal activity status between the two groups (p = 0.10). Mild to moderate and moderate to severe restriction was reported in 16/35 (46%) and 8/35 (23%) IT patients and 14/37 (38%) and 4/37 (11%) non-IT patients respectively (Table S3). There were no significant differences in disease activity at 2 weeks, 4 weeks and 2 months (Table S5), and systemic treatment was generally consistent between the groups (Table S6, Supporting Information Text). We present the largest evaluation of IT therapy in FHL to date, including 78 patients from the international collaborative HLH-2004 study with confirmed FHL and CNS involvement at HLH-2004 treatment onset, of whom 37 received IT therapy within the first 2 months. The size of the IT group and the non-IT group, along with the subgroups of patients with neurological alterations and abnormal CSF at onset, were well matched. However, more IT patients had an abnormal MRI at onset compared to non-IT patients; 63% versus 31% (p = 0.046). Neuroradiological changes as an isolated CNS manifestation were rare, consistent with Charpentier et al., who also found that neuroradiological changes did not correlate with different neurological signs; therefore, they were not included in our analyses.15 In our study, neurological symptoms in the IT group had not normalized at 2 months to a greater extent compared to the non-IT group (IT = 38%; non-IT = 61%). Neither differences in overall disease activity nor differences in systemic treatment between the groups explained the apparent lack of effectiveness of IT therapy (see also Supporting Information Text). Our findings align with the HLH-94 study, where neurological symptoms normalized in 10 of 15 children who received IT therapy and in 10 of 15 children who did not.12 Furthermore, the IT group did not show a lower rate of neurological symptoms after the first 2 months (IT = 31%; no IT = 14%) nor fewer cases of psychomotor retardation (IT = 15%, non-IT = 17%; p = 1.0). This study has several limitations, especially regarding patient selection and confounding factors. IT treatment was not randomized, and due to a lack of data on clinical neurological alterations at 2 weeks, as well as incomplete CSF data in many cases, it was not possible to determine which patients met the criteria for recommended IT therapy; ‘progressive neurological symptoms during the first 2 weeks or an abnormal cerebrospinal fluid value at onset that had not improved after 2 weeks’. Therefore, an indication bias is possible, and the absence of outcome differences could be the case of an effective treatment being given to a higher risk group of patients. Additionally, the rate of missing CSF data is a limitation, although information on neurological alterations, the main focus of the study, was mostly complete at onset (78/78, 100%) and follow-up (74/78, 95%). Furthermore, assessing neurological alterations, especially psychomotor retardation, is difficult in severely ill young children and is relevant here, because most patients were younger than 1 year at diagnosis. Finally, the multicentre design increases the risk of inconsistent neurological evaluations across centres. In conclusion, the data do not support a higher rate of normalization of neurological alterations in already symptomatic FHL patients, nor less CNS involvement at 2 months follow-up within the IT group. This lack of apparent clinical efficacy raises the question of whether IT therapy should be recommended for treating FHL. Our findings emphasize the need for further research, such as prospective clinical studies, animal studies and collaborative data analyses, to clarify the role of intrathecal therapy in FHL and to develop data-driven recommendations. J-IH, MA and SL contributed to planning the HLH-2004 study, with J-IH as Principal Investigator. KZ and J-IH planned the current study; J-IH, IA, EI, KL, MM and VN recruited patients; KZ compiled data and performed statistical analyses; EB performed data entry and compiled data; KZ, EB and J-IH analysed results; KZ drafted the manuscript under the supervision of JIH, which was then reviewed and approved by all authors. The authors are grateful to all reporting clinicians. The work was supported by grants to JIH from the Swedish Children's Cancer Fund (KP2021-0006 and KP2024-0012), the Swedish Cancer Society (Dnr 233 162 Pj), Region Stockholm (ALF-project; FoUI-998 983) and the Cancer- and Allergy Foundation of Sweden (Ref no 10118). None of the authors have any conflicts of interest to disclose relevant to the current study. The HLH-2004 study (Supporting Information Text, Figure S1) was approved by the Ethics Committee of the Karolinska Institute (2004-219/3). Informed consent was obtained. The HLH-2004 study was registered at clinicaltrials.gov, identifier: NCT00426101. Individual participant data cannot be shared because this was not applied for in the ethical application. Tables S1–S6. Figure S1. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.