Peripheral blood 8 colour flow cytometry monitoring of hairy cell leukaemia allows detection of high‐risk patients

Abstract

SummaryAlthough purine analogues have significantly improved the outcome of hairy cell leukaemia (HCL) patients, 30-40% relapse, illustrating the need for minimal residual disease (MRD) markers that can aid personalized therapeutic management. Diagnostic samples from 34 HCL patients were used to design an 8-colour flow cytometry (8-FC) tube for blood MRD (B/ RD) analysis (188 samples) which was compared to quantitative IGH polymerase chain reaction (Q-PCR) on 83 samples and to qualitative consensus IGH PCR clonality analysis on 165 samples. Despite heterogeneous HCL phenotypes at diagnosis, discrimination from normal B lymphocytes was possible in all cases using a single 8-FC tube, with a robust sensitivity of detection of 10 À4, comparable to Q-PCR at this level, but preferable in terms of informativeness, simplicity and cost. B/RD assessment of 15 patients achieving haematological complete remission after purine analogues was predictive of a clinically significant relapse risk: with a median follow-up of 95 months; only one of the nine patients with reproducible 8-FC B/RD levels below 10 À4 (B/RD neg ) relapsed, compared to 5/6 in the B/ RD pos group (P = 0Á003). These data demonstrate the clinical interest of a robust 8-FC HCL B/RD strategy that could become a surrogate biomarker for therapeutic stratification and new drug assessment, which should be evaluated prospectively.

Is there a role for minimal residual disease monitoring in the management of patients with hairy‐cell leukaemia?

“…FC‐based MRD has a number of advantages over bone marrow (BM) biopsies for disease evaluation: (i) it can be determined in either peripheral blood (PB) or BM; (ii) it is highly sensitive, being able to identify one tumour cell among 10 000 normal cells (0·01%); and (iii) the turnaround time is relatively short. In HCL, however, the association between MRD and progression‐free survival (PFS) or overall survival (OS) has remained elusive (Tallman et al , ; Cervetti et al , ; Garnache Ottou et al , ). Moreover, there is a lack of consensus regarding the most appropriate timing for evaluation, type of sample (PB versus BM) or cut‐off level for MRD positivity.…”

“…Phenotypically, HCL cells are characterised by the expression of CD19, CD20 and CD22, together with CD11c, CD25, CD103 and CD123. These markers can be determined by flow cytometry (FC), which allows for an accurate diagnosis and minimal residual disease (MRD) monitoring (Garnache Ottou et al , ). FC‐based MRD has a number of advantages over bone marrow (BM) biopsies for disease evaluation: (i) it can be determined in either peripheral blood (PB) or BM; (ii) it is highly sensitive, being able to identify one tumour cell among 10 000 normal cells (0·01%); and (iii) the turnaround time is relatively short.…”

Hairy cell leukemia: 2020 update on diagnosis, risk stratification, and treatment

“…The clinical interest to investigate blood MRD was initially demonstrated, with a high risk of relapse in patients with positive testing for MRD and a low risk in patients with negative testing. The 1/9 patients who achieved hematological response and MRD < 10 −4 on at least two consecutive blood samples during the first 2 years after PNA treatment relapsed as compared to 5/6 patients with MRD > 10 −4 . When using eight weekly rituximab infusions a month after initial cladribine therapy, 19% of patients achieved undetectable MRD after cladribine and the proportion of patients achieving a negative MRD status increased after the administration of rituximab with 76% of the untreated patients achieving subsequently a negative MRD status .…”

Long-term follow-up after purine analogue therapy in hairy cell leukaemia

“…For this assessment a good-quality BM trephine biopsy with immunohistochemistry is the gold standard. However, evidence is emerging that alternatives more acceptable to patients, such as 8-colour flow cytometry using peripheral blood or a BM aspirate, may in future be used instead of a trephine biopsy without loss of accuracy [48]. With pentostatin this assessment should be performed after 8 to 10 cycles of treatment when the full blood count has returned to normal (though lymphopenia will persist) [25], [26], [27].…”