Laboratory validation and clinical utility of next-generation sequencing-based IGH/TCR clonality testing for the monitoring of measurable residual disease in acute lymphoblastic leukaemia: real-world experience at Austin Pathology.

Measurable residual disease (MRD) testing is an essential aspect of disease prognostication in acute lymphoblastic leukaemia (ALL) and informs clinical decisions. The depth of MRD clearance is highly relevant and requires assays with sufficient sensitivity. Austin Pathology is one of the few laboratories in Australia currently utilising a fully validated and National Association of Testing Authorities (NATA)-accredited ultrasensitive next-generation sequencing (NGS) platform for MRD monitoring in ALL. This technology is based on the detection of clonal rearrangement of immunoglobulin and T cell receptor genes in leukaemic cells, and is capable of achieving a limit of detection at least one to two logs below that of multiparametric flow cytometry (MFC). In this retrospective analysis, we report a clonotype detection rate of up to 85.7% at diagnosis, and a concordance rate of 78.7% in MRD results between NGS and MFC. Of the discordant samples, nearly all were NGS+/MFC-, highlighting the superior sensitivity of NGS. The enhanced sensitivity is clinically relevant, as discordant MRD results often heralded fulminant relapse, and therefore offer clinicians additional lead time and a window of opportunity to initiate pre-emptive therapy. Notwithstanding a small and heterogeneous cohort, our real-world survival data indicate an intermediate relapse risk for NGS+/MFC- patients. In light of recent approval of Medicare rebatable ALL MRD testing, we discuss how NGS can complement other techniques such as MFC in personalising management strategies. We recommend routine clonality testing by NGS at diagnosis and use a multi-modality approach for subsequent MRD monitoring.

Alectinib induces marked red cell spheroacanthocytosis in a near-ubiquitous fashion and is associated with reduced eosin-5-maleimide binding.

We reviewed haematological investigations for 43 patients treated at a single centre with alectinib, an inhibitor of anaplastic lymphoma kinase (ALK) which is considered standard first-line treatment for patients with ALK-rearranged advanced non-small cell lung cancer. Ninety-five percent of patients developed marked acanthocytosis, echinocytosis and/or spheroacanthocytosis, not observable with prior treatment with other ALK-inhibitors. Anaemia developed in 73% of patients (38% <100 g/L, 8% <80 g/L), though definite new haemolysis was present in only 11%. Eosin-5-maleimide binding was reduced in all assessed patients, and increased membrane cholesterol was identified in one patient assessed with lattice light sheet microscopy. We have identified a previously undescribed phenomenon whereby alectinib induces red cell membrane abnormalities in nearly all patients through an unclear, but likely ALK-independent, mechanism, resulting in mild anaemia without universal haemolysis.

ALK-positive histiocytosis: an expanded clinicopathologic spectrum and frequent presence of KIF5B-ALK fusion.

In 2008, we presented three cases of ALK-positive histiocytosis as a novel systemic histiocytic proliferation of early infancy with hepatosplenomegaly and dramatic hematological disturbances. This series of 10 cases (including the original three cases) describes an expanded clinicopathological spectrum and the molecular findings of this histiocytic proliferation. Six patients had disseminated disease: five presented in early infancy with eventual disease resolution, and the sixth presented at 2 years of age and died of intestinal, bone marrow, and brain involvement. The other four patients had localized disease involving nasal skin, foot, breast, and intracranial cavernous sinus - the first three had no recurrence after surgical resection, while the cavernous sinus lesion showed complete resolution with crizotinib therapy. The lesional histiocytes were very large, with irregularly folded nuclei, fine chromatin, and abundant eosinophilic cytoplasm, sometimes with emperipolesis. There could be an increase in foamy histiocytes and Touton giant cells with time, resembling juvenile xanthogranuloma. Immunostaining showed that the histiocytes were positive for ALK, histiocytic markers (CD68, CD163) and variably S100, while being negative for CD1a, CD207, and BRAF-V600E. Next-generation sequencing-based anchored multiplex PCR (Archer® FusionPlex®) performed in six cases identified KIF5B-ALK gene fusion in five and COL1A2-ALK fusion in one. There was no correlation of gene fusion type with disease localization or dissemination. The clinicopathological spectrum of ALK-positive histiocytosis is broader than originally described, and this entity is characterized by frequent presence of KIF5B-ALK gene fusion. We recommend that every unusual histiocytic proliferative disorder, especially disseminated lesions, be tested for ALK expression because of the potential efficacy of ALK inhibitor therapy in unresectable or disseminated disease.

Arterial thromboembolic disease: a single-centre case series study.

AIM: Paediatric venous thromboembolic disease has been reported with increased frequency during the last decade. In contrast, the pathophysiology of arterial thromboembolic disease in infants and children has not been adequately explored. The aim of this study was to determine the prevalence, aetiology, diagnostic criteria, management and outcome of arterial thromboembolism (TE) in a tertiary paediatric centre. METHODS: A prospective, single-centre registry was established at an Australian tertiary paediatric centre in order to address the aim of this study. RESULTS: One-hundred-and-two arterial thrombotic events occurred in 98 patients during 48 months. Infants were most likely to have a lower limb arterial TE (n = 22) whilst children were most likely to have a central nervous system arterial TE (n = 26). Surgery was a frequent predisposing factor in both infants and children. Doppler ultrasonography, computerized tomography and magnetic resonance imaging were the most commonly used diagnostic modalities. Unfractionated heparin was the most frequently used treatment in both age groups. At discharge, 25 infants and twelve children had complete resolution of their arterial TE. Direct thrombosis-related mortality was 4% in infants and 9% in children. Duration of follow-up ranged from 1 to 900 days, with thirteen infants and 32 children never achieving complete resolution. Forty-nine percent of post-discharge survivors had significant long term sequelae directly attributable to their arterial TE. CONCLUSION: Arterial TE occurred as frequently as venous TE in our tertiary paediatric population. The clinical outcome and long term sequelae of such events are significant.

Assessing the outcome of systemic tissue plasminogen activator for the management of venous and arterial thrombosis in pediatrics.

This study sought to ascertain the outcomes of systemic thrombolytic therapy used in a cohort of infants and children. Complete thrombus resolution was achieved in 81% of patients with arterial thromboses (n=16) compared to 0% of children with venous thromboses (n=10). A major bleeding rate of 11.5% occurred across the entire cohort (n=3, all arterial). In our cohort, no patient with venous thromboembolism achieved complete resolution of their thrombosis after thrombolytic therapy. More cohort studies reporting the outcome of uniform protocols of thrombolytic therapy in children are required.

The prognostic impact of bone marrow involvement in patients with diffuse large cell lymphoma varies according to the degree of infiltration and presence of discordant marrow involvement.

BACKGROUND: The prognostic significance of marrow involvement in diffuse large cell lymphoma (DLCL) is controversial. Factors that that have been reported to influence prognosis include the pattern and extent of marrow infiltration and histological discordance between the primary site and the bone marrow. METHODS: Bone marrow biopsies from 172 patients with newly diagnosed DLCL entered in two consecutive trials of the Australasian Leukaemia and Lymphoma Group were analyzed. Progression-free (PFS) and overall survival (OS) were calculated according to the absence or presence of bone marrow involvement (BMI), the extent of lymphomatous infiltration and the presence of histological discordance between the primary site and the bone marrow. RESULTS: Of 172 patients with DLCL accrued between 1982 and 1990, who were treated with CHOP or CHOP-like regimens, 47 (27%) demonstrated marrow involvement on examination of multiple levels. Seventy two percent (34/47) of patients had discordant marrow involvement (<50% large cells) and 28 had minimal (<10%) involvement; these latter patients with minimal marrow involvement (<10%) had similar PFS & OS to the 113 patients without involvement. Within the group of 47 patients with marrow involvement, an increasing percentage of BM involvement was significantly associated with an increasing percentage of concordant histology and a decreasing PFS & OS. CONCLUSIONS: Minimal BMI, seen in the majority of patients with DLCL with marrow infiltration, appears not to influence the PFS & OS. However, an increasing degree of marrow involvement is associated with an increasing component of large cells and a poorer prognosis in DLCL patients, independent of other risk factors.