FxCycle™ Based Ploidy Correlates with Cytogenetic Ploidy in B-Cell Acute Lymphoblastic Leukemia and Is Able to Detect the Aneuploid Minimal Residual Disease CloneKey terms

Background Flow cytometry (FCM) is a simple, sensitive, and specific technique that can potentially determine DNA ploidy in B-cell precursor ALL (BCP-ALL) and is complementary to cytogenetics. Methods A prospective FCM DNA ploidy analysis using FxCycle (TM) Violet (assay sensitivity 0.01%) was done in 125 consecutive new cases of BCP-ALL (90 cases <15 years of age) and compared with corresponding cytogenetic ploidy (karyotyping and/or FISH) data wherever available. This assay was also subsequently evaluated for detection of residual aneuploid clone in few BCP-ALL cases. Results Of the total 125 BCP-ALL cases evaluated, flow ploidy analysis revealed diploidy (DI 0.96-1.05) in 44.8% (n = 56), low-hyperdiploidy (DI 1.06 to 1.15) in 13.6% (n = 17), high-hyperdiploidy (DI 1.16-1.39) in 32.8% (n = 41) and near-tetraploidy (DI >= 1.80) in 2.4% (n = 3) cases. The high risk sub-group of low-hypodiploidy (DI 0.70 to 0.88)/near-triploidy (DI 1.40 to 1.79) constituted 5.6% (n = 7) cases while there was only one case with haploidy (DI 0.58). Overall, high concordance of 90.4% (n = 113) was noted between the combined cytogenetics ploidy and FCM ploidy. Of the total discordant cases (n = 12), the maximum discordance was seen in the low-hyperdiploid DI subgroup (n = 10), which included seven cases with low DNA index high hyperdiploidy (LDI-HHD). FCM DNA ploidy assay was able to detect the residual clone in all six MRD positive aneuploid cases evaluated. Conclusions FxCycle (TM) based DNA ploidy ascertains strong correlation with cytogenetic profiles and yields complementary information that can be used by the cytogenetics laboratories or otherwise. (c) 2019 International Clinical Cytometry Society