Minimal residual disease detection by flow cytometry in adult T-cell leukemia/lymphoma

Abstract

Little information exists regarding the detection of minimal residual disease (MRD) in adult T-cell leukemia/lymphoma (ATLL). We evaluated 75 peripheral blood samples from 17 ATLL cases using flow cytometry (FC); 50 of the samples were concurrently evaluated by polymerase chain reaction (PCR) for clonal T-cell receptor gamma chain (TRG) gene rearrangement and the presence of human T-cell lymphotropic virus-1 proviral sequences. Residual ATLL cells were identified using a multiparametric approach to identify aberrant T-cell immunophenotypes. Malignant T cells were CD4+, CD3 dim+, CD26-, CD25 bright, CD7+, and CD27+, with occasional dim expression of CD2 or CD5. FC exhibited a high sensitivity, detecting as few as 0.29% ATLL cells/WBC (4.9 cells/microL) in the peripheral blood. PCR for TRG gene rearrangement was slightly more sensitive, and FC and PCR complemented each other in detecting MRD. In 2 patients, there was complete remission; 4 patients had disease refractory to therapy, and 3 died; 11 others had persistent disease with variable numbers of ATLL cells in the peripheral blood. Higher levels of ATLL cells appeared to correlate with disease severity. FC detection of aberrant T cells permits sensitive and quantitative monitoring of MRD in ATLL.

Figure 1

Minimal residual disease (CD26−/CD4+ cells) in 17 patients with adult T-cell leukemia/lymphoma (ATLL). The time shown on the right is the follow-up period. Patients 4, 7, and 8 were unresponsive to treatment and died of disease progression. Patient 15 continued with daclizumab treatment after initial treatment with denileukin diftitox.

Image 1

Representative flow cytometric analysis of adult T-cell leukemia/lymphoma cells in peripheral blood samples. The lymphoid cells were gated by forward light scatter vs side light scatter. The leukemic cells are indicated in red. A, The leukemic cells show typical immunophenotype: CD3 dim/CD7−/CD4+/CD25+/CD26−. B, The leukemic cells displayed a nearly normal level of expression of CD3 with a small subset dim for CD3 and were CD4+ and CD7−/CD26−. C, The leukemic cells were partially positive for CD7, slightly dim for CD3, and CD4+/CD26−. APC, allophycocyanin; FITC, fluorescein isothiocyanate; PE, phycoerythrin; PerCP, peridinin chlorophyll protein.