Optimizing FISH Results in Multiple Myeloma: Plasma Cell Selection via Flow Cytometry
Cancer Genetics and Therapeutics
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Primary Categories:
- Laboratory Genetics
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Secondary Categories:
- Laboratory Genetics
Introduction:
Multiple myeloma is a malignancy of plasma cells in the bone marrow. Identification of abnormal plasma cells can be done by flow cytometry. Current genetic testing for prognosis and evaluation of multiple myeloma includes chromosomal analysis, fluorescence in situ hybridization (FISH), and next-generation sequencing. FISH is critical for identifying genetic abnormalities that are associated with disease risk and treatment outcomes.
In cases with a low percentage of abnormal plasma cells, plasma cell separation improves the sensitivity of FISH by enriching the sample with plasma cells, thereby increasing the likelihood of detecting relevant genetic abnormalities.
Our study aims to establish a threshold for the percentage of clonal plasma cells that correlates with positive FISH findings, providing a practical guide for selecting cases that would benefit from plasma cell separation. By identifying this threshold, we can streamline the testing process, ensuring that FISH is utilized efficiently for cases most likely to yield clinically relevant genetic information.
Methods:
Bone marrow was collected from 144 patients diagnosed with multiple myeloma. Flow cytometry was performed to characterize plasma cells. FISH was performed to detect common chromosomal abnormalities associated with multiple myeloma, including probes to target the following genomic regions: CSK1B (1q21), CDKN2C (1p32), FGFR3 (4p16), chromosome 9 centromere, CCND1 (11q13), RB1 (13q14), IGH (14q32), chromosome 15 centromere, MAF (16q23), TP53 (17p13.1), and MAFB (20q12).
Flow cytometry was used to quantify the percentage of abnormal cells in each patient. Patients were then divided into groups based on their percentage of abnormal plasma cells (0-0.09%, 0.1-0.4%, 0.41-1.0%, 1.1-2%, 2.1-5%, 5-10%, 10.1-100%). For each group, we calculated the percentage of cases with positive FISH results. Comparisons between groups were then made to assess any correlations between FISH findings and the percentage of abnormal plasma cells.
Results:
Positive FISH results were observed in 34 cases and 110 cases had no FISH findings. Only 4% of the patients in the <0.09% (n=24) group had positive FISH results. 42% of the patients that had 0.1-0.4% of abnormal plasma cells had positive FISH results. 60% of the patients with 0.41-1.0% abnormal plasma cells had positive FISH results. The percentage of positive FISH results reached 100% for the 1.1-2.0% abnormal plasma cell group and stayed at 75% or greater for all groups with more than 1.1% of abnormal plasma cells.
Conclusion:
Identifying genetic abnormalities in multiple myeloma cases is critical for diagnosis, prognosis, and treatment planning. We investigated various multiple myeloma cases to correlate the percentage of abnormal plasma cells as determined by flow cytometry and the FISH findings of those patients. Our initial study showed that cases with ≥ 1.1% abnormal plasma cells had a positive FISH finding at least 75% of the time indicating a potential threshold for cases that would benefit from plasma cell separation. A larger cohort of multiple myeloma cases is required to further refine this threshold limit. This study seeks to identify a threshold for abnormal plasma cell levels that reliably predicts positive FISH results in patients with multiple myeloma and determine which cases would benefit from plasma cell separation.
Multiple myeloma is a malignancy of plasma cells in the bone marrow. Identification of abnormal plasma cells can be done by flow cytometry. Current genetic testing for prognosis and evaluation of multiple myeloma includes chromosomal analysis, fluorescence in situ hybridization (FISH), and next-generation sequencing. FISH is critical for identifying genetic abnormalities that are associated with disease risk and treatment outcomes.
In cases with a low percentage of abnormal plasma cells, plasma cell separation improves the sensitivity of FISH by enriching the sample with plasma cells, thereby increasing the likelihood of detecting relevant genetic abnormalities.
Our study aims to establish a threshold for the percentage of clonal plasma cells that correlates with positive FISH findings, providing a practical guide for selecting cases that would benefit from plasma cell separation. By identifying this threshold, we can streamline the testing process, ensuring that FISH is utilized efficiently for cases most likely to yield clinically relevant genetic information.
Methods:
Bone marrow was collected from 144 patients diagnosed with multiple myeloma. Flow cytometry was performed to characterize plasma cells. FISH was performed to detect common chromosomal abnormalities associated with multiple myeloma, including probes to target the following genomic regions: CSK1B (1q21), CDKN2C (1p32), FGFR3 (4p16), chromosome 9 centromere, CCND1 (11q13), RB1 (13q14), IGH (14q32), chromosome 15 centromere, MAF (16q23), TP53 (17p13.1), and MAFB (20q12).
Flow cytometry was used to quantify the percentage of abnormal cells in each patient. Patients were then divided into groups based on their percentage of abnormal plasma cells (0-0.09%, 0.1-0.4%, 0.41-1.0%, 1.1-2%, 2.1-5%, 5-10%, 10.1-100%). For each group, we calculated the percentage of cases with positive FISH results. Comparisons between groups were then made to assess any correlations between FISH findings and the percentage of abnormal plasma cells.
Results:
Positive FISH results were observed in 34 cases and 110 cases had no FISH findings. Only 4% of the patients in the <0.09% (n=24) group had positive FISH results. 42% of the patients that had 0.1-0.4% of abnormal plasma cells had positive FISH results. 60% of the patients with 0.41-1.0% abnormal plasma cells had positive FISH results. The percentage of positive FISH results reached 100% for the 1.1-2.0% abnormal plasma cell group and stayed at 75% or greater for all groups with more than 1.1% of abnormal plasma cells.
Conclusion:
Identifying genetic abnormalities in multiple myeloma cases is critical for diagnosis, prognosis, and treatment planning. We investigated various multiple myeloma cases to correlate the percentage of abnormal plasma cells as determined by flow cytometry and the FISH findings of those patients. Our initial study showed that cases with ≥ 1.1% abnormal plasma cells had a positive FISH finding at least 75% of the time indicating a potential threshold for cases that would benefit from plasma cell separation. A larger cohort of multiple myeloma cases is required to further refine this threshold limit. This study seeks to identify a threshold for abnormal plasma cell levels that reliably predicts positive FISH results in patients with multiple myeloma and determine which cases would benefit from plasma cell separation.