Will a Peripheral Blood (PB) Sample Yield the Same Diagnostic and Prognostic Cytogenetic Data as the Concomitant Bone Marrow (BM) In Myelodysplasia? An International Study Comparing Cytogenetics and Interphase FISH Using Parallel PB and BM Samples

Abstract 2922

The myelodysplastic syndromes (MDS) are a heterogeneous group of hematological malignancies characterized by ineffective hematopoiesis and a highly variable clinical course, for which novel treatments are beginning to emerge. Conventional cytogenetic studies (CCS) of bone marrow (BM) are routinely used in clinical practice to detect abnormal clones in proliferating (metaphase) cells, identifying clonal aberrations in ∼50% of de novo MDS cases. Cytogenetics is also one of the key International Prognostic Scoring System (IPSS) components used to estimate overall survival and leukemia-free survival in MDS. Chromosome abnormalities may be quantified at presentation and during treatment by the use of fluorescence in situ hybridization (FISH) with DNA probes for specific chromosome loci (e.g., chromosomes 5, 7, 8 and 20) in non-proliferating (interphase) nuclei. However, it is not clear whether or not peripheral blood CCS will yield the same diagnostic and prognostic data as bone marrow CCS at disease presentation or whether patients without apparent chromosome abnormalities by CCS have “hidden” abnormalities that can be identified by interphase FISH. To answer these questions, 15 members of the International Working Group on MDS Cytogenetics agreed to perform CCS and FISH in parallel on both peripheral blood and bone marrow samples collected from MDS patients. To be certain that all participating sites scored and interpreted their individual FISH data in a similar fashion, a quality assurance (QA) study was completed with each site studying two identical test (proficiency) samples. Concordance among sites was very good to excellent allowing for the establishment of a standardized protocol with clear scoring criteria before patient samples were processed. In the second phase of the study, a total of 77 MDS patients were accrued to the study with 61% showing an abnormal karyotype. A FISH panel consisting of eight probe sets [-5/5q-, -7/7q-/der(1;7), +8/8q-, -11/+11/11q-/add(11q), 12p-/+21/t(12;21), -13/13q-, 17p- and 20q-/i(20q)/i(20p), Abbott Molecular, Inc.] was performed on both specimen types. While CCS was frequently unsuccessful (57.5%) in the PB specimens, FISH was informative (concordant with BM/PB CCS) in 92% of cases, with 49% of PB FISH demonstrating an abnormal clone. FISH was discordant in 4 of 77 BM and PB samples (5%), while CCS and FISH on BM and PB were discordant in 6 of 77 BM specimens (8%) and 6 of 73 PB specimens (8%). The data suggest that evaluation of interphase nuclei from PB on follow-up (non-diagnostic) FISH studies on MDS patients will be equally informative (and less costly and stressful) as a BM sample.