Minimal residual disease detection in mantle cell lymphoma: methods and significance of four-color flow cytometry compared to consensus IGH-polymerase chain reaction at initial staging and for follow-up examinations.

BACKGROUND The increasing application of multi-color flow cytometry assays for staging and follow-up in mantle cell lymphoma necessitates that the specificity and sensitivity of this technique are evaluated. Data from prospective clinical trials comparing the clinical applicability of flow cytometry to routine diagnostic methods and to polymerase chain reaction are currently lacking. DESIGN AND METHODS We applied a standardized four-color flow cytometry assay to 281 prospectively collected peripheral blood and bone marrow samples from 98 patients with mantle cell lymphoma participating in a multi-center clinical trial and compared the results to those obtained with conventional clinical staging and consensus primer IGH-polymerase chain reaction. RESULTS The maximum sensitivity of flow cytometry using light chain restriction in CD19+CD5+ subpopulations was 8.0 x 10(-4) while flow cytometry that relied on immunophenotypic aberrations was less sensitive (2.4 x 10(-3)). Mantle cell lymphoma cells were detected in 87.3% of 110 pre-treatment samples from 84 patients by flow cytometry and in 94.5% by polymerase chain reaction. Eight out of 84 patients (9.5%) diagnosed clinically as having stage II or III disease showed peripheral blood or bone marrow involvement according to flow cytometry, thus documenting more advanced disease. At follow-up residual lymphoma cells were detected by flow cytometry and concordantly by polymerase chain reaction in 10/171 samples (5.8%); however, 31 follow-up samples (18.1%) were positive for minimal residual disease according only to polymerase chain reaction analysis. CONCLUSIONS The sensitivity of four-color flow cytometry is comparable to that of IGH-polymerase chain reaction at initial staging but is less sensitive at follow-up after immuno-chemotherapy. Both techniques are highly valuable methods for accurate initial staging.