Faster clinical decisions in B-cell acute lymphoblastic leukaemia: A single flow cytometric 12-colour tube improves diagnosis and minimal residual disease follow-up.

Assessing minimal residual disease (MRD) in B-cell precursor acute lymphoblastic leukaemia (BCP-ALL) is essential for adjusting therapeutic strategies and predicting relapse. Quantitative polymerase chain reaction (qPCR) is the gold standard for MRD. Alternatively, flow cytometry is a quicker and cost-effective method that typically uses leukaemia-associated immunophenotype (LAIP) or different-from-normal (DFN) approaches for MRD assessment. This study describes an optimized 12-colour flow cytometry antibody panel designed for BCP-ALL diagnosis and MRD monitoring in a single tube. This method robustly differentiated hematogones and BCP-ALL cells using two specific markers: CD43 and CD81. These and other markers (e.g. CD73, CD66c and CD49f) enhanced the specificity of BCP-ALL cell detection. This innovative approach, based on a dual DFN/LAIP strategy with a principal component analysis method, can be used for all patients and enables MRD analysis even in the absence of a diagnostic sample. The robustness of our method for MRD monitoring was confirmed by the strong correlation (r = 0.87) with the qPCR results. Moreover, it simplifies and accelerates the preanalytical process through the use of a stain/lysis/wash method within a single tube (<2 h). Our flow cytometry-based methodology improves the BCP-ALL diagnosis efficiency and MRD management, offering a complementary method with considerable benefits for clinical laboratories.

Anthracycline-induced cardiotoxicity on regional myocardial work and left ventricular mechanical dispersion in adolescents and young adults in post-lymphoma remission.

BACKGROUND: Myocardial work (MW) is a new echocardiographic tool with a high sensitivity to detect early and subtle alterations of myocardial function. We aimed to evaluate the late effects of anthracyclines by assessing the global and segmental MW and intraventricular mechanical dispersion from speckle tracking echocardiography in childhood lymphoma survivors (CLS). METHODS: Thirty-one young adults including CLS and age-matched healthy controls were enrolled. All underwent echocardiography including an evaluation of left ventricular (LV) morphology and regional function. We assessed LV longitudinal (differentiating sub-endocardial and sub-epicardial layers), circumferential strains and twist, global and regional MW index (MWI). LV mechanical dispersion was assessed from the time dispersion of LV longitudinal strain, from myocardial wasted work (MWW) and myocardial work efficiency (MWE). RESULTS: The longitudinal strains both at the level of the sub-endocardium and sub-epicardium were reduced in CLS compared to controls. The global MWI was also decreased (1668 ± 266 vs 1870 ± 264%.mmHg in CLS patients and controls, respectively, p < 0.05), especially on the apical segments. An increase of LV intraventricular mechanical dispersion was observed in CLS. MWW and MWE remained unchanged compared to controls. CONCLUSION: Our results strongly support that cardiac remodeling is observed in CLS, characterized by a decrease in MW and an increase in LV mechanical dispersion. The apex is specifically altered, but its clinical significance remains uncertain. MW as a complement to strain seems interesting in cancer survivors to detect myocardial dysfunction at early stage and adapt their follow-up.

Fitness and metabolic response to exercise in young adult survivors of childhood lymphoma.

PURPOSE: Childhood lymphoma survivors (CLSs) are at high risk of reduced daily activity. This work studied metabolic substrate use and cardiorespiratory function in response to exercise in CLSs. METHODS: Twenty CLSs and 20 healthy adult controls matched for sex, age, and BMI took an incremental submaximal exercise test to determine fat/carbohydrate oxidation rates. Resting echocardiography and pulmonary functional tests were performed. Physical activity level, and blood metabolic and hormonal levels were measured. RESULTS: CLSs reported more physical activity than controls (6317 ± 3815 vs. 4268 ± 4354 MET-minutes/week, p = 0.013), had higher resting heart rate (83 ± 14 vs. 71 ± 13 bpm, p = 0.006), and showed altered global longitudinal strain (- 17.5 ± 2.1 vs. - 19.8 ± 1.6%, p = 0.003). We observed no difference in maximal fat oxidation between the groups, but it was reached at lower relative exercise intensities in CLSs (Fatmax 17.4 ± 6.0 vs. 20.1 ± 4.1 mL/kg, p = 0.021). At V̇O2 peak, CLSs developed lower relative exercise power (3.2 ± 0.9 vs. 4.0 ± 0.7 W/kg, p = 0.012). CONCLUSION: CLSs reported higher levels of physical activity but they attained maximal fat oxidation at lower relative oxygen uptake and applied lower relative power at V̇O2 peak. CLSs may thus have lower muscular efficiency, causing greater fatigability in response to exercise, possibly related to chemotherapy exposure during adolescence and childhood. Long-term follow-up is essential and regular physical activity needs to be sustained.

Pediatric multicellular tumor spheroid models illustrate a therapeutic potential by combining BH3 mimetics with Natural Killer (NK) cell-based immunotherapy.

The induction of apoptosis is a direct way to eliminate tumor cells and improve cancer therapy. Apoptosis is tightly controlled by the balance of pro- and antiapoptotic Bcl-2 proteins. BH3 mimetics neutralize the antiapoptotic function of Bcl-2 proteins and are highly promising compounds inducing apoptosis in several cancer entities including pediatric malignancies. However, the clinical application of BH3 mimetics in solid tumors is impeded by the frequent resistance to single BH3 mimetics and the anticipated toxicity of high concentrations or combination treatments. One potential avenue to increase the potency of BH3 mimetics is the development of immune cell-based therapies to counteract the intrinsic apoptosis resistance of tumor cells and sensitize them to immune attack. Here, we describe spheroid cultures of pediatric cancer cells that can serve as models for drug testing. In these 3D models, we were able to demonstrate that activated allogeneic Natural Killer (NK) cells migrated into tumor spheroids and displayed cytotoxicity against a wide range of pediatric cancer spheroids, highlighting their potential as anti-tumor effector cells. Next, we investigated whether treatment of tumor spheroids with subtoxic concentrations of BH3 mimetics can increase the cytotoxicity of NK cells. Notably, the cytotoxic effects of NK cells were enhanced by the addition of BH3 mimetics. Treatment with either the Bcl-XL inhibitor A1331852 or the Mcl-1 inhibitor S63845 increased the cytotoxicity of NK cells and reduced spheroid size, while the Bcl-2 inhibitor ABT-199 had no effect on NK cell-mediated killing. Taken together, this is the first study to describe the combination of BH3 mimetics targeting Bcl-XL or Mcl-1 with NK cell-based immunotherapy, highlighting the potential of BH3 mimetics in immunotherapy.

Unleashing the power of NK cells in anticancer immunotherapy.

Due to their physiological role in removing damaged cells, natural killer (NK) cells represent ideal candidates for cellular immunotherapy in the treatment of cancer. Thereby, the cytotoxicity of NK cells is regulated by signals on both, the NK cells as well as the targeted tumor cells, and the interplay and balance of these signals determine the killing capacity of NK cells. One promising avenue in cancer treatment is therefore the combination of NK cell therapy with agents that either help to increase the killing capacity of NK cells or sensitize tumor cells to an NK cell-mediated attack. In this mini-review, we present different strategies that can be explored to unleash the potential of NK cell immunotherapy. In particular, we summarize how modulation of apoptosis signaling within tumor cells can be exploited to sensitize tumor cells to NK cell-mediated cytotoxicity.

Assessment of the architecture and integrity of frozen-thawed testicular tissue from (pre)pubertal boys with cancer.

BACKGROUND: Testicular tissue freezing is proposed for fertility preservation to (pre)pubertal boys with cancer before highly gonadotoxic treatment. Studies accurately comparing human (pre)pubertal testicular tissue quality before freezing and after thawing are exceptional. No study has reported this approach in a systematic manner and routine care. OBJECTIVES: To assess the impact of a control slow freezing protocol on testicular tissue architecture and integrity of (pre)pubertal boys after thawing. MATERIALS AND METHODS: (Pre)pubertal boys (n = 87) with cancer from 8 Reproductive Biology Laboratories of the French CECOS network benefited from testicular tissue freezing before hematopoietic stem cell transplantation. Seminiferous tubule cryodamage was determined histologically by scoring morphological alterations and by quantifying intratubular spermatogonia and the expression of DNA replication and repair marker in frozen-thawed testicular fragments. RESULTS: A significant increase in nuclear and epithelial score alterations was observed after thawing (p < 0.0001). The global lesional score remained lower than 1.5 and comparable to fresh testicular tissue. The number of intratubular spermatogonia and the expression of DNA replication and repair marker in spermatogonia and Sertoli cells did not vary significantly after thawing. These data showed the good preservation of the seminiferous tubule integrity and architecture after thawing, as previously reported in our studies performed in prepubertal mice and rats. DISCUSSION: The current study reports, for the first time, the development of a semi-quantitative analysis of cryodamage in human (pre)pubertal testicular tissue, using a rapid and useful tool that can be proposed in routine care to develop an internal and external quality control for testicular tissue freezing. This tool can also be used when changing one or several parameters of the freezing-thawing procedure. CONCLUSION: Control slow freezing protocol without seeding maintains the seminiferous tubule architecture and integrity, the concentration of spermatogonia and the expression of DNA replication and repair marker in spermatogonia and Sertoli cells after thawing.

Characterization and Manipulation of the Crosstalk Between Dendritic and Natural Killer Cells Within the Tumor Microenvironment.

Cellular therapy has entered the daily clinical life with the approval of CAR T cell therapeutics and dendritic cell (DCs) vaccines in the US and the EU. In addition, numerous other adoptive cellular products, including natural killer (NK) cells, are currently evaluated in early phase I/ II clinical trials for the treatment of cancer patients. Despite these promising accomplishments, various challenges remain to be mastered in order to ensure sustained therapeutic success. These include the identification of strategies by which tumor cells escape the immune system or establish an immunosuppressive tumor microenvironment (TME). As part of the innate immune system, DCs and NK cells are both present within the TME of various tumor entities. While NK cells are well known for their intrinsic anti-tumor activity by their cytotoxicity capacities and the secretion of pro-inflammatory cytokines, the role of DCs within the TME is a double-edged sword as different DC subsets have been described with either tumor-promoting or -inhibiting characteristics. In this review, we will discuss recent findings on the interaction of DCs and NK cells under physiological conditions and within the TME. One focus is the crosstalk of various DC subsets with NK cells and their impact on the progression or inhibition of tumor growth. In addition, we will provide suggestions to overcome the immunosuppressive outcome of the interaction of DCs and NK cells within the TME.

Peripheral blood stem cell collection in children with extremely low body weight (≤8 kg). What have we learned over the past 25 years and where are the limits?

Hematopoietic progenitor cells-apheresis (HPC-A) collection is now a routine procedure for autologous hematopoietic stem cell transplantation. Here we present our 25 years' experience of HPC-A collection in children weighing 8 kg or less, with a focus on the evolution of our standard operating procedures, and the safety limits for these young patients, in the Pediatric Apheresis Unit of Clermont-Ferrand University Hospital (France). Fifteen children weighing 8 kg or less underwent 26 HPC-A collections over 25 years. Median CD34+ cell yield by leukapheresis was 4.4 106 /kg. No procedure-related complications were encountered during or after the collection. No patient had profound thrombocytopenia or anemia that needed post-collection transfusions. Our experience in pediatric oncology patients who underwent HPC-A collections shows that this procedure can be performed even in the smallest of children with no increase in toxicity provided all precautions are taken to ensure that the procedure is carried out under the ideal conditions.

[Access to fertility preservation for adolescents and young adults aged 15 to 24 years with cancers in Auvergne, France]. / Accès à la préservation de la fertilité des adolescents et jeunes adultes de 15 à 24 ans atteints de cancers en Auvergne, France.

INTRODUCTION: Cancers of adolescents and young adults have particular epidemiological specificities. The improvement in their survival should be accompanied by an increased consideration of the treatments' side effects, among which the potential decrease in fertility. The objective of the study was to describe the access to fertility preservation of these patients at the University Hospital of Clermont-Ferrand over a period of 3 years. METHODS: During this retrospective descriptive study, various socio-demographic and clinical data were collected. RESULTS: One hundred and fifty new cases of cancers were diagnosed in patients aged 15 to 24 years. Forty-four percent received at least one fertility consultation, 29 % for girls and 58 % for boys (P<0.001). The number of cases that did not result in fertility preservation was significantly higher for girls than boys (P=0.005). Fertility preservation was mainly achieved by cryopreservation of ovarian tissue in female adolescents, ovocytes in young women and sperm in boys. DISCUSSION: We observed sex disparities in access to fertility preservation. Despite the existence of recommendations, progress remains to be made. The establishment of clinico-biological platforms should allow a better awareness of patients and professionals, and thus promote access to fertility preservation techniques for young patients with cancer.

Childhood Leukemia Survivors and Metabolic Response to Exercise: A Pilot Controlled Study.

BACKGROUND: Leukemia is the most common cancer in pediatrics, with many late effects such as higher risk of dyslipidemia, insulin resistance, obesity, and metabolic syndrome. The objective of this work was to investigate substrate oxidation during submaximal exercise in survivors of childhood acute leukemia. METHODS: A total of 20 leukemia survivors and 20 healthy children were matched by sex, age, and Tanner stage. They all took a submaximal incremental exercise test to determine fat and carbohydrate oxidation rates. RESULTS: Cardiorespiratory fitness was significantly lower in leukemia survivors, with lower relative VO2 peaks (p < 0.001), lower heart rate values (p = 0.02), and lower exercise power (p = 0.012), whereas rest metabolism and body mass index did not differ between the two groups. During exercise, upward of heart rate relative to VO2 peak was significantly higher (p < 0.001) in childhood leukemia survivors. We found lower carbohydrate and fat oxidation rates (p = 0.07) in leukemia survivors compared with healthy children, and also a significantly lower relative maximal fat oxidation rate (p = 0.014). CONCLUSION: Despite impaired physical fitness and metabolic response to exercise, childhood leukemia survivors remained sensitive to physical activity interventions, and could readily adapt to submaximal exercise intensity.

Sensitive and Specific Detection of Ewing Sarcoma Minimal Residual Disease in Ovarian and Testicular Tissues in an In Vitro Model.

Ewing sarcoma (EWS) is a common pediatric solid tumor with high metastatic potential. Due to toxic effects of treatments on reproductive functions, the cryopreservation of ovarian tissue (OT) or testicular tissue (TT) is recommended to preserve fertility. However, the risk of reintroducing residual metastatic tumor cells should be evaluated before fertility restoration. Our goal was to validate a sensitive and specific approach for EWS minimal residual disease (MRD) detection in frozen germinal tissues. Thawed OT (n = 12) and TT (n = 14) were contaminated with tumor RD-ES cells (10, 100, and 1000 cells) and EWS-FLI1 tumor-specific transcript was quantified with RT-qPCR. All contaminated samples were found to be positive, with a strong correlation between RD-ES cell numbers and EWS-FLI1 levels in OT (r = 0.93) and TT (r = 0.96) (p < 0.001). No transcript was detected in uncontaminated control samples. The invasive potential of Ewing cells was evaluated using co-culture techniques. After co-culturing, tumor cells were detected in OT/TT with histology, FISH, and RT-qPCR. In addition, four OT and four TT samples from children with metastatic EWS were tested, and no MRD was found using RT-qPCR and histology. We demonstrated the high sensitivity and specificity of RT-qPCR to detect EWS MRD in OT/TT samples. Clinical trial: NCT02400970.

In vitro assessment of edoxaban anticoagulant effect in pediatric plasma.

INTRODUCTION: Anticoagulant therapy in pediatric patients remains an issue and safer therapies, such as direct oral anticoagulants could overcome the limitations of conventional anticoagulant treatments in this population. Edoxaban, a factor Xa inhibitor, is used for the prevention and treatment of venous thromboembolism. Due to its pharmacokinetic characteristics, edoxaban is a promising candidate molecule for children. This study compared edoxaban in vitro effect in children and adults. MATERIALS AND METHODS: Blood samples were prospectively collected from 87 adults and 97 children (n = 12: <2 year-old; n = 8: 2-4 year-old; n = 9: 5-7 year-old; n = 14: 8-9 year-old; n = 10: 10-13 year-old; n = 15: 14-15 year-old; and n = 29: 16-18 year-old). Plasma samples were supplemented in vitro with edoxaban to a final concentration of 50, 150 or 300 ng/mL, and then edoxaban effect on prothrombin time (PT), activated partial thromboplastin time (aPTT), fibrinogen (Clauss assay), specific anti-factor Xa activity and thrombin generation assay (TGA) (with 5pM tissue factor and 4 nM phospholipids) was evaluated. RESULTS: PT, aPTT, and specific anti-Xa activity exhibited similar dose-dependent responses to edoxaban in the different age groups. The reduction of thrombin peak, the most edoxaban-sensitive TGA parameter, was similar in adults and children, but for the youngest group (<2 year-old) where the peak value reduction (median [Q1-Q3]) was higher than in adults (51% [44-59] versus 40% [32-46], p < 0.01; 74% [63-80] versus 65% [58-70], p < 0.05; and 84% [73-88] versus 76% [70-80], p < 0.05 for 50, 150 and 300 ng/mL edoxaban, respectively). CONCLUSIONS: Edoxaban in vitro effect are comparable in children and adults except in the <2-year-old group.

Very long-term molecular follow-up of minimal residual disease in patients with neuroblastoma.

In high-risk neuroblastoma (HR-NB), the clinical significance of long-term minimal residual disease (MRD) monitoring using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for neuroblastoma mRNAs has not been investigated. We report long-term MRD follow-ups of four patients with HR-NB throughout the disease (diagnosis, remission, and relapse) and treatment course (chemotherapy, autologous and allogeneic stem cell transplantation, and donor lymphocyte and natural killer cell infusions). The results showed the stability of mRNA marker expression after different treatments and demonstrated their validity to predict relapse and assess therapeutic response. This opens up the possibility of investigating the utility of long-term molecular monitoring of MRD in prospective multicenter studies.

[Fertility preservation in oncology]. / Préservation de la fertilité en cancérologie.

Since the improvement of cancer diagnosis and treatment, survival rates of these patients increase. Gonadal damages are frequent consequences of cancer treatments with different evidence of impaired fertility. In this context, fertility preservation should be proposed to patients exposed to potentially gonadotoxic treatments. Different preservation approaches may be proposed depending on patient age, sex, cancer type and type of treatment. The indications of fertility preservation depend on sexual maturity. In young girls, ovarian cortex cryopreservation is the only technique feasible in order to preserve their reproductive potential. Vitrification of oocytes which needs ovarian stimulation or oocytes in vitro maturation is becoming more commonly performed for pubertal women to preserve their fertility. Ovarian cortex freezing could be offered to emergency fertility preservation of adult female cancer patients. In prepubertal boys, testicular tissue cryopreservation is the only line treatment for fertility preservation. For future use, various approaches are being evaluated such as spermatogonial stem cell injection or in vitro maturation. Cryopreservation of spermatozoa is, today, an established and successful technique for male adults. When there are no spermatozoa in ejaculate, sperm can be retrieved after treatment of testicular biopsy. The French bioethics law clearly indicates that fertility preservation should be proposed to patients exposed to potentially gonadotoxic treatment. Today, many approaches are possible. Fertility preservation indications are based on multidisciplinary consultations within platforms for the fertility preservation in order to optimize the patient care.

RT-qPCR for PHOX2B mRNA is a highly specific and sensitive method to assess neuroblastoma minimal residual disease in testicular tissue.

Neuroblastoma (NB) is the most common type of extracranial solid tumor in children with a high prevalence in toddlers. For childhood cancer survivors, preservation of reproductive potential is an important factor for quality of life. The optimization of NB minimal residual disease (MRD) detection in testicular tissue is crucial to evaluate the risk of malignant cell reintroduction. The first step in the present study was to assess the accuracy of reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to detect tyrosine hydroxylase (TH), paired-like homeobox 2b (PHOX2B) and doublecortin (DCX) mRNA expression in frozen/thawed testicular tissues of patients with non-obstructive azoospermia (NOA) contaminated (in vitro model) with an increasing number of IMR-32 and SK-N-SH NB cells. Testicular tissues were frozen by slow or snap freezing. The second step was to determine the expression levels of these markers in testicular samples from 4 pre-pubertal males (2 with stage IV NB and 2 with non-NB malignancy). The yield of extracted RNA was similar in testicular samples frozen by slow or snap freezing. In the in vitro model, TH and DCX transcripts were detected in uncontaminated testicular tissues, whereas PHOX2B mRNA was not detected. There was a strong positive association between the number of NB cells used for contamination and PHOX2B transcript levels. For IMR-32 and SK-N-SH NB cell lines, specificity and sensitivity rates of detection were 100% for PHOX2B following in vitro contamination with 10 tumor cells. In testicular samples from pre-pubertal males with and without NB, PHOX2B mRNA expression was not observed, but high expression levels of TH and DCX mRNA were detected, which were similar to expression detected in the in vitro model. Among the markers used in blood and bone marrow for NB MRD studies, the detection of PHOX2B transcripts by RT-qPCR may provide an accurate assessment of NB cells in testicular tissues from males who require fertility preservation.

Highly sensitive assessment of neuroblastoma minimal residual disease in ovarian tissue using RT-qPCR-A strategy for improving the safety of fertility restoration.

BACKGROUND: Ovarian tissue cryopreservation (OTC) is the only option available to preserve fertility in prepubertal females with neuroblastoma (NB), a childhood solid tumor that can spread to the ovaries, with a risk of reintroducing malignant cells after an ovarian graft. PROCEDURE: We set out to determine whether the analysis of TH (tyrosine hydroxylase), PHOX2B (paired-like homeobox 2b), and DCX (doublecortin) transcripts using quantitative reverse transcriptase polymerase chain reaction (RT-qPCR) could be used to detect NB contamination in ovarian tissue. Analyses were performed on benign ovarian tissue from 20 healthy women between November 2014 and September 2015 at the University Hospital of Clermont-Ferrand. Pericystic benign ovarian tissues were collected and contaminated with increasing numbers of human NB cells (cell lines IMR-32 and SK-N-SH) before detection using RT-qPCR. RESULTS: TH and DCX transcripts were detected in uncontaminated ovarian tissue from all the donors, hampering the detection of small numbers of tumor cells. By contrast, PHOX2B was not detected in any uncontaminated ovarian fragment. PHOX2B levels were significantly increased from 10 NB cells. Our study is the first to evaluate minimal residual disease detection using NB mRNAs in human ovarian tissue. Only PHOX2B was a reliable marker of NB cells contaminating ovarian tissue. CONCLUSIONS: These results are encouraging and offer hope in the near future for grafting ovarian tissue in women who survive cancer, whose fertility has been jeopardized by treatment, and who could benefit from OTC without oncological risk.

Cryopreservation of ovarian tissue in pediatric patients undergoing sterilizing chemotherapy.

Significantly improved survival rates in children and adolescents with cancer have put fertility preservation high on the pediatric oncology agenda. Here we report a retrospective single-center study of 13 years experience of ovarian tissue cryopreservation (OTC) before sterilizing treatment in order to define the safety/benefits of OTC and study clinical/hormonal outcomes in girls. From 2000 to 2013, OTC was performed in 36 girls: eight had non-malignant disease and 28 had malignant disease. Laparoscopy was used to collect a third of each ovary that was frozen by a slow cooling protocol. Indications for OTC were 13 auto-, 19 allo-stem-cell-transplantation and 4 sterilizing chemotherapy. Ovarian tissue harvested by intraumbilical laparoscopy led to no major postoperative complications and did not delay chemotherapy. Histological analysis of ovarian tissue showed an average of 9 primordial follicles/mm(2) [0-83] and no malignant cells were identified. Median post-harvest follow-up was 36 months [1-112]: 26 girls were alive in complete remission and 10 had died. Hormonal results were evaluable for 27 patients (median age 17 yrs [5-26]): 16 patients were in premature ovarian insufficiency. OTC sampling one third of each ovary appears to be an appropriate approach to preserve fertility in children without consequences on subsequent therapeutic program.

Leukapheresis in management of hyperleukocytosis in children's leukemias.

We describe 16 leukapheresis (LK) procedures performed in 7 children with different types of leukemia and hyperleukocytosis. We also provide an analysis of previously published experiences of pediatric LK. Median age and body weight of patients were 12.3 years (range, 0.2 to 16.7 y) and 49 kg (range, 5 to 61 kg). Immediate pre-first-LK median white blood cell count was 478×10/L (108×10/L to 988×10/L). All cytoreduction were performed on Cobe Spectra cell separator. Sixty-eight percent of procedures were performed with peripheral veins. Extracorporeal line had been primed with red blood cell for 31% of LK. The median decrease in white blood cell count after each LK was 33% (0% to 69%), and overall decrease after completion of LK procedures was 62% (11% to 94%). Only minor clinical adverse events and no metabolic complication were attributable to LK. No more clinical symptom of hyperleukocytosis was observed after completion of LK procedures. Our findings are consistent with reported results in other pediatric series: LK is a well-tolerated procedure that can be safely performed with an experienced pediatric team even on the smallest children.