Droplet digital polymerase chain reaction for the assessment of disease burden in hairy cell leukemia

Abstract

BRAFV600E mutation is the pathogenic driver of hairy cell leukemia (HCL) found in the vast majority of cases both at onset and during recurrences. The identification of the mutated allele in blood and marrow correlates with the presence of neoplastic cells and can be considered a marker of active disease. Likewise, the absence of the mutation after treatment may indicate a state of deep response. The BRAFV600E burden was measured by droplet digital polymerase chain reaction (ddPCR) and expressed as fractional abundance in 35 HCL patients at different stages of disease (onset, relapse, complete response [CR] after treatment, long‐term remission) in peripheral blood and/or bone marrow (when available). Mean values of fractional abundance for patients at diagnosis, relapse and response, respectively, were 12.26%, 16.52% and 0.02% in peripheral blood and 23.51%, 13.96% and 0.26% in bone marrow. Four patients out of 6 evaluated at response were molecularly negative for BRAFV600E in peripheral blood. Mean fractional abundance in peripheral blood tested in 14 patients with long lasting CR was 0.05%, and 10 patients were BRAFV600E negative. These preliminary results suggest that ddPCR permits to assess the active tumor burden in HCL at different disease phases and support the hypothesis that some patients in CR qualify for a molecular CR.

A 3-decade multicenter European experience with cladribine as upfront treatment in 384 patients with hairy cell leukemia

“…MRD was not an endpoint of our study. Although it may be hypothesized that some patients have obtained MRD negativity, 5 it is of note that deep disease control is achieved in a significant proportion of cases with only 1 course of treatment. More than 50% of treated patients, in fact, required no further therapy beyond upfront cladribine.…”

“…1,2 More specifically, cladribinetreated patients can achieve complete recovery of peripheral blood cytopenia and disappearance of marrow infiltration by hematoxylin and eosin staining in 80% to 90% of cases, as reported in the literature, 3 albeit some complete responder patients still display residual marrow disease detectable by immunohistochemistry or molecular techniques. 4,5 Besides that, a significant proportion of patients could maintain an efficient disease control over time with only 1 treatment course, possibly enjoying very long-lasting treatment-free intervals and having a chance of being cured.…”

Hairy Cell Leukemia and HCL-Like Disorders: Diagnosis and TreatmentLeuc閙ie �Tricholeucocytes et Autres Prolif閞ations �Cellules Chevelues: Diagnostic et Traitement

“…Il peut être important de préciser notamment chez le sujet jeune si la RC est associée à une maladie résiduelle (MRD) indétectable (MRDu). La MRD peut être étudiée par de nombreuses techniques: immunohistochimie [68,69], PCR allèle spécifique [70], PCR digitale [71,72] ou CMF [73]. Des efforts d'harmonisation sont nécessaires pour permettre la comparaison des résultats entre les différents laboratoires [74]: pour les techniques de biologie moléculaire, la recherche de MRD doit être précédée d'un séquençage IGHV qui n'est pas forcément réalisé en pratique.…”

Consensus opinion from an international group of experts on measurable residual disease in hairy cell leukemia

“…Two recent studies have utilized digital droplet PCR (ddPCR) for the detection of BRAF V600E mutation in HCL [ 41 , 42 ]. Guerrini and colleagues used the assay in 27 patients with HCL as well as 2 with HCLv and 18 with splenic marginal zone lymphoma and concluded that the assay was more sensitive than quantitative PCR and as specific and therefore very useful for detecting MRD [ 41 ].…”

“…Similarly, Broccoli and colleagues measured the burden of BRAF V600E mutant in peripheral blood or bone marrow specimens from 35 patients with HCL at various stages of disease and reported mean values of fractional disease burden at diagnosis, relapse and response to be 12.26%, 16.52%, and 0.02% in peripheral blood and 23.51%, 13.96%, and 0.26% in bone marrow. The mean value in peripheral blood among 14 patients with long-standing CR was 0.05% including 10 patients who were negative by the assay [ 42 ]. These results suggest that ddPCR for BRAF V600E may be a useful assay for long-term monitoring of the disease.…”