Correlation between conventional karyotype, interphase FISH and immunophenotype in risk stratification of newly diagnosed plasma cell myeloma: An observational study

Background: Plasma cell myeloma (PCM) is a common adult hematological neoplasm of terminally differentiated B-cells resulting in accumulation of monoclonal plasma cells. PCM is heterogeneous disease with survival time varies from months to years, determined by age, stage, cytogenetics abnormalities, and treatment response. There is conflicting evidence in role of immunophenotype as a prognostic indicator. This study identified frequency of cytogenetics abnormalities and established correlation between cytogenetics and immunophenotyping in risk stratification in newly diagnosed PCM.

Methods: Pilot study was undertaken on 30 newly diagnosed PCM over 4 years. Apart from extensive myeloma laboratory and imaging profile, multicolor flow cytometry using panel of CD138, CD38, CD45, CD56, CD19, CD20, CD28, CD200, CD117, κ, and λ light-chains. Karyotyping was done using GTG banding and interphase fluorescence in situ hybridization analysis on magnetically sorted plasma cells for t(4;14), t(11;14), del(13)q, and del(17)p probes.

Results: Of 30 myeloma patients, 16(53.3%) were men with mean age 57.23 ± 11.90 years. The del(13)q was commonest cytogenetics abnormality. CD56-positive cases were strongly associated with presence of del(17)p and stage III of disease (p < 0.05). Negative expression of CD117 was seen in advanced stage of disease and high-risk genetic factor, t(4;14) (p = 0.049). Absent CD28 expression was associated with higher albumin levels, lower levels of β2MG, and lack of high-risk genetic abnormalities. Advanced clinical stages were associated with expression of CD56, CD28, and absent expression of CD45 and CD117.

Conclusion: Immunophenotypic antigens positive and negative expressions are associated with high-risk genetic abnormalities and advanced clinical stages of PCM.

Institution ethic committee reference number: IEC/2017/230, AFMC, Pune.