Interphase fluorescence in situ hybridization analysis of CD19-selected cells: Utility in detecting disease in post-therapy samples of B-cell neoplasms

Abstract

Context: The detection of low-level persistent or relapsed B-cell neoplasms, particularly post-therapy, can be challenging, often requiring multiple testing modalities. Objective: Here we investigate the utility of CD19-based selection of neoplastic B-cells (CD19S) as an enrichment strategy to improve the detection rate of cytogenetic abnormalities in post-therapy samples of B-cell neoplasms, especially those with low-level disease. Design: In a cohort largely comprised of post-therapy B-ALL and CLL samples, we performed fluorescence in situ hybridization (FISH) analysis on CD19-selected cells (CD19S FISH) in 128 specimens from 88 patients, and on non-selected cells (NS FISH) in a subset of cases. The FISH findings were compared with the concurrent flow cytometry (FC) results in all samples and molecular analysis in a subset. Results: CD19S FISH was able to detect cytogenetic aberrations in 86.0% of post-therapy samples with evidence of disease as determined by routine or MRD FC, compared to 59.1% of samples by NS FISH. CD19S FISH detected significantly higher percentages of positive cells compared to NS FISH (p < 0.001). Importantly, CD19S FISH enabled the detection of emergent subclones (clonal evolution) associated with poor prognosis. Conclusions: CD19S FISH can be useful in daily diagnostic practice. Compared to NS FISH, CD19S FISH is quantitatively and qualitatively superior for the detection of cytogenetic aberrations in B-cell neoplasms, which are important for risk stratification and optimal management of patients with B-cell neoplasms, especially in the relapsed setting. Although CD19S FISH has a diagnostic sensitivity inferior to that of MRD FC, the sensitivity of this modality is comparable to routine FC for the evaluation of low-level disease in the post-therapy setting. Moreover, CD19S samples are invaluable for additional molecular and genetic analyses.