Terminal deoxynucleotidyl transferase (TdT)-positive cells in cerebrospinal fluid and development of overt CNS leukemia: a 5-year follow-up study in 113 children with a TdT-positive leukemia or non- Hodgkin's lymphoma

Abstract

We investigated whether an indirect nuclear terminal deoxynucleotidyl transferase (TdT) immunofluorescence (IF) assay on single cells present in the cerebrospinal fluid (CSF) is more effective than conventional cytomorphology for early detection or exclusion of (minimal) meningeal leukemic infiltration in patients with a TdT+ malignancy. During a 5- year follow-up study, 1,661 consecutive CSF samples from 113 children with a TdT+ acute lymphoblastic leukemia (ALL) (n = 100), a TdT+ acute nonlymphoblastic leukemia (ANLL) (n = 8), or a TdT+ non-Hodgkin's lymphoma (NHL) (n = 5) were analyzed. In 1,511 (91.9%) of 1,643 evaluable CSF samples, the positive and negative findings of both cytomorphology and the TdT-IF assay were concordant. In 47 (2.9%) samples from 28 patients, the cytomorphology was suspect while the TdT- IF assay was negative; follow-up as long as 58 months revealed no CNS leukemia in any patient. In 85 (5.2%) samples, cytomorphology was negative (n = 70) or suspect (n = 15) but TdT+ cells were detected. RBC contamination seriously hampered evaluation in 31 of these 85 samples. From the remaining 54 TdT+ samples from 29 patients, 40 samples preceded overt CNS leukemia in 20 patients. Two consecutive findings of TdT+ cells in the CSF were always followed by overt CNS leukemia. At initial diagnosis, 11 children had TdT+ cells in their RBC-free CSF. In one of these children, morphology was suspect; a repeated lumbar puncture was positive on both assays. Thus, initial CNS leukemia was diagnosed. In the other ten children, morphology was negative. In six of them, CNS leukemia was diagnosed 2 to 20 months later. In 32 other children examined at initial diagnosis, neither TdT+ cells nor blasts were observed in the CSF. In none of these patients was a CNS leukemia diagnosed after a follow-up of 2.5 to 57 months (median 24 months). In 207 control CSF samples from 58 children with TdT- oncologic, hematologic, or infectious diseases, no TdT+ cells could be detected. The TdT-IF assay is easy to perform and is a more reliable diagnostic tool for detection of CNS leukemia at an early stage than is cytomorphology. At initial diagnosis, the finding of Tdt+ cells in a RBC-free CSF sample with a negative cytomorphology is highly predictive for development of overt CNS leukemia.

New cellular markers at diagnosis are associated with isolated central nervous system relapse in paediatric B‐cell precursor acute lymphoblastic leukaemia

“…High WBC, the presence of TdT-positive cells in CSF at diagnosis and T-ALL phenotype are known to be associated with CNS relapse (Hooijkaas et al, 1989;Januszkiewicz & Nowak, 1995;Gajjar et al, 2000;Burger et al, 2003). Indeed, CNS relapses were relatively more common in T-ALL (~27%) than BCP-ALL (~13%), but WBC showed considerable overlap between patients with or without an isolated CNS relapse, limiting its use for stratification.…”

“…Clearly, extramedullary (EM) involvement is much more frequent at relapse than at initial diagnosis, as only a small subset of ALL patients (1-4%) present with overt CNS involvement at diagnosis (Conter et al, 2000;Eden et al, 2000;Gaynon et al, 2000;Kamps et al, 2000;Pui et al, 2000;Schrappe et al, 2000;Silverman et al, 2000). However, submicroscopic CNS involvement may appear in up to 40% of patients (Hooijkaas et al, 1989;Januszkiewicz & Nowak, 1995;Hagedorn et al, 2007).…”

“…Whereas current strategies for MRD detection allow identification of most ALL patients at risk of BM relapse (van Dongen et al, 1998;Willemse et al, 2002;Van Velden et al, 2009), MRD measurements in BM might not reliably predict (isolated) CNS relapses. High white blood cell count (WBC), terminal deoxynucleotidyl transferase (TdT) positive cells in cerebrospinal fluid (CSF) at diagnosis and T-ALL phenotype are associated with CNS relapse (Hooijkaas et al, 1989;Januszkiewicz & Nowak, 1995;Gajjar et al, 2000;Burger et al, 2003) but have limited value for therapy stratification, because high WBC, TdT+ CSF cells and T-ALL phenotype are found in many patients that do not develop CNS relapse (Goulden et al, 1994;Neale et al, 1994;O'Reilly et al, 1995;Nathan et al, 2004;Hagedorn et al, 2007).…”

Pitfalls in the diagnosis of childhood leukaemia

“…We normally repeat the CSF after 4–6 weeks without giving more intrathecal therapy, to avoid masking the diagnosis. Immunophenotyping (Hooijkaas et al , 1989) may be helpful in this situation, and cytogenetics or fluorescence in situ hybridization (FISH) may prove useful if adequate material can be obtained.…”

Minimal requirements for the diagnosis, classification, and evaluation of the treatment of childhood acute lymphoblastic leukemia (ALL) in the “BFM family” cooperative group

“…The finding that cytomorphologically suspicious cells are TdT-negative may exclude CNS leukemia; the finding of TdT positivity (in red blood cell-free samples!) is highly predictive of, but not decisive for, CNS involvement [60,63,64].…”