Contributions
Abstract: PB1603
Type: Publication Only
Background
Flow cytometry (FCM) is a simple technique that can accurately determine DNA ploidy in B-cell precursor ALL (BCP-ALL).
Aims
We tried to analyze the applicability of FxCycleTM based DNA ploidy analysis in risk stratification of BCP ALLs at diagnosis. We also tried to assess the utility of FCM ploidy for monitoring Minimal Residual Disease (MRD) during follow-up.
Methods
A prospective FCM DNA ploidy analysis using FxCycleTM Violet dye was done in 125 consecutive new cases of BCP-ALL from May 2016 to July 2017. The FCM DNA Index (DI) was compared with karyotyping / FISH data wherever available. As a pilot study, in 16 MRD positive cases (n=6 with hyperdiploid diagnostic DI and n=10 diploid diagnostic DI), DNA ploidy based MRD analysis was also performed.
Results
Of the total 125 cases (age range 10 months - 66 years, M:F ratio 1.7:1), n=90 (72%) were pediatric (aged ≤ 15 years). Karyotype was available in n=119 cases (with 77.3% success rate). Overall cytogenetic ploidy was assessed by both karyotyping and FISH in n=81 cases, only karyotype in n=11 cases and only FISH in n=33 cases. Flow ploidy analysis revealed diploidy (DI 0.96 - 1.05) in 56/125 (44.8%), low-hyperdiploidy (DI 1.06 to 1.15) in 17/125 (13.6%), high-hyperdiploidy (DI 1.16 – 1.39) in 41/125 (32.8%) and near-tetraploidy (DI ≥ 1.80) in 3/125 (2.4%) cases. The high-risk sub-group (Figure 1) of Low-Hypodiploidy (DI 0.70 to 0.88) / Near-triploidy (DI 1.40 to 1.79) (i.e. endoreduplication) was seen in n=7 (5.6%) cases while one single case had near haploidy (DI 0.58) with modal chromosome number (MN) 25. Of the 56 cases with diploid DI, successful karyotype was available in n=39 cases of which 10/39 (25.6%) were classic diploids (46,XX or 46,XY) while 29/39 (74.4%) were pseudo-diploids having additional balanced / un-balanced translocations or structural chromosomal abnormalities. Of the n=17 low hyperdiploid DI cases, n=7 cases were concordant with cytogenetic ploidy (MN 47-50 and/ or by FISH) while n=7 cases had MN > 50 fitting with description of low DNA index high hyperdiploid subtype (LDI-HHD). Of the n=41 high-hyperdiploid DI cases (karyotype available in n=29 cases), n=26 cases had MN 51-65 (FISH concordant), while in n=15 cases FISH alone confirmed high-hyperdiploidy. DNA ploidy (DI of hematogones 0.96 - 1.05) could confirm the residual hyperdiploid clone in n=6/6 hyperdiploid MRD positive cases tested.
Conclusion
FxCycle based DNA ploidy analysis is simple, sensitive and specific technique, which is complementary to cytogenetics in the diagnosis as well as follow-up of BCP-ALLs.
Session topic: 1. Acute lymphoblastic leukemia – Biology & Translational Research
Keyword(s): B cell acute lymphoblastic leukemia, Cell cycle, Cytogenetics, flow cytometry
Abstract: PB1603
Type: Publication Only
Background
Flow cytometry (FCM) is a simple technique that can accurately determine DNA ploidy in B-cell precursor ALL (BCP-ALL).
Aims
We tried to analyze the applicability of FxCycleTM based DNA ploidy analysis in risk stratification of BCP ALLs at diagnosis. We also tried to assess the utility of FCM ploidy for monitoring Minimal Residual Disease (MRD) during follow-up.
Methods
A prospective FCM DNA ploidy analysis using FxCycleTM Violet dye was done in 125 consecutive new cases of BCP-ALL from May 2016 to July 2017. The FCM DNA Index (DI) was compared with karyotyping / FISH data wherever available. As a pilot study, in 16 MRD positive cases (n=6 with hyperdiploid diagnostic DI and n=10 diploid diagnostic DI), DNA ploidy based MRD analysis was also performed.
Results
Of the total 125 cases (age range 10 months - 66 years, M:F ratio 1.7:1), n=90 (72%) were pediatric (aged ≤ 15 years). Karyotype was available in n=119 cases (with 77.3% success rate). Overall cytogenetic ploidy was assessed by both karyotyping and FISH in n=81 cases, only karyotype in n=11 cases and only FISH in n=33 cases. Flow ploidy analysis revealed diploidy (DI 0.96 - 1.05) in 56/125 (44.8%), low-hyperdiploidy (DI 1.06 to 1.15) in 17/125 (13.6%), high-hyperdiploidy (DI 1.16 – 1.39) in 41/125 (32.8%) and near-tetraploidy (DI ≥ 1.80) in 3/125 (2.4%) cases. The high-risk sub-group (Figure 1) of Low-Hypodiploidy (DI 0.70 to 0.88) / Near-triploidy (DI 1.40 to 1.79) (i.e. endoreduplication) was seen in n=7 (5.6%) cases while one single case had near haploidy (DI 0.58) with modal chromosome number (MN) 25. Of the 56 cases with diploid DI, successful karyotype was available in n=39 cases of which 10/39 (25.6%) were classic diploids (46,XX or 46,XY) while 29/39 (74.4%) were pseudo-diploids having additional balanced / un-balanced translocations or structural chromosomal abnormalities. Of the n=17 low hyperdiploid DI cases, n=7 cases were concordant with cytogenetic ploidy (MN 47-50 and/ or by FISH) while n=7 cases had MN > 50 fitting with description of low DNA index high hyperdiploid subtype (LDI-HHD). Of the n=41 high-hyperdiploid DI cases (karyotype available in n=29 cases), n=26 cases had MN 51-65 (FISH concordant), while in n=15 cases FISH alone confirmed high-hyperdiploidy. DNA ploidy (DI of hematogones 0.96 - 1.05) could confirm the residual hyperdiploid clone in n=6/6 hyperdiploid MRD positive cases tested.
Conclusion
FxCycle based DNA ploidy analysis is simple, sensitive and specific technique, which is complementary to cytogenetics in the diagnosis as well as follow-up of BCP-ALLs.
Session topic: 1. Acute lymphoblastic leukemia – Biology & Translational Research
Keyword(s): B cell acute lymphoblastic leukemia, Cell cycle, Cytogenetics, flow cytometry