Normal SFLC Ratio in Newly Diagnosed Myeloma: A Potential Biomarker of Non-High-Risk and Nonaggressive Disease

The myeloma patients with baseline normal/near-normal serum free light chain (SFLC) ratio have been reported to respond favorably to the treatment, unlike patients with extreme/abnormal SFLC ratio. We hypothesized that this normal SFLC ratio could serve as a biomarker for favorable cytogenetic and outcome profiles.

The flow cytometric immunophenotyping (FCM-IPT) and interphase FISH analysis of marrow aspirate were performed as per recommended guidelines, in all the newly diagnosed patients of plasma cell proliferative disorders, enrolled during this prospective study. Patients were risk-stratified as per ISS, R-ISS, and R2-ISS criteria. The outcome evaluation, in patients treated with standard 3-/4-drugs induction, was done at least 3 months after initiation of therapy.

A total of 306 patients with plasma cell proliferative disorders were enrolled; myeloma patients were 240 (n_SFLC = 23/240, 9.6%) and (ab_SFLC = 217/240, 90.4%). IgG lambda M-protein was more significantly seen in (n_SFLC) patients. None of the patients in the (n_SFLC) group showed circulating blood plasma cells. The (n_SFLC) patients did not show the presence of TP53 gene deletion and relatively lacked other high-risk genetics. The outcome analysis showed that more patients in the (n_SFLC) group attained ≥ VGPR (88.9% vs. 65.4% of ab_SFLC).

Based on this, we infer that the patients with a normal SFLC ratio are enriched with non-high-risk features and behave less aggressively.