BACKGROUND

Deeper depth of response (DpR) after induction therapy, especially gain of negative minimal residual disease (MRD), has been linked to prolonged survival in multiple myeloma (MM). However, flow-MRD examination focuses on the numbers but not on the biological characteristics of residual plasma cells (PCs).

OBJECTIVES

To explore whether the genetic features of residual tumor cells affect the survival time of patients with MM.

DESIGN

A retrospective cohort study.

METHODS

We investigated the clonality of cytogenetic abnormalities (CAs) of the residual PCs using interphase fluorescence hybridization (iFISH) in the National Longitudinal Cohort of Hematological Diseases in China (NCT04645199). Here, a longitudinal cohort of 269 patients with patient-paired diagnostic and post-induction iFISH results was analyzed.

RESULTS

Persistent CAs after induction therapy were detected in about half of the patients (118/269, 43%), and patients with undetectable CAs showed significantly improved survival compared with those with genetically detectable MRD [median progression-free survival (mPFS): 59.7 35.7 months, < 0.001; median overall survival (mOS): 97.1 68.8 months, = 0.011]. In addition, different patterns of therapy-induced clonal evolution were observed by comparing the clonal structure of residual PCs with paired baseline samples. Patients who maintained at a high risk during follow-up had the worst survival (mPFS: 30.5 months; mOS: 54.4 months), while those who returned to lower risk or had iFISH- at both time points had the best survival (mPFS: 62.0 months, mOS: not reached).

CONCLUSION

These findings highlighted the prognostic value of genetic testing in residual tumor cells, which may provide a deep understanding of clonal evolution and guide clinical therapeutic strategies.