Impact of Novel M-Component Based Biomarkers On to Progression Free Survival After Treatment in Intact Immunoglobulin Multiple Myeloma.

Multiple Myeloma (MM) is characterized by bone marrow (BM) plasma cell infiltration and the presence of serum/urine monoclonal immunoglobulin (Ig). The depth of response has been associated with longer PFS in MM causing subsequent prolonged survival.

Recently novel M-based biomarker immunoassays have been developed (Freelite™, Hevylite™) and their significance in MM diagnosis and prognosis has been demonstrated.^1,2  Furthermore serum Free Light Chains (sFLC) are used for better assessment of treatment response, thus patients are considered to achieve stringed Complete Response (sCR) by having CR criteria plus normal serum Free Light Chains Ratio (sFLCR) and absent clonal cells on BM.³  The significance of Hevylite™ on response has not been assessed so far. Patients in nCR or better do not automatically restore their ratio of intact monoclonal Ig/intact polyclonal Ig of the same class (Hevylite™ or HLCR). We therefore investigated the importance of sFLCR and HLCR normalisation at plateau on PFS, in a series of patients with intact Ig MM.

50 intact immunoglobulin MM patients were studied from diagnosis to last follow up. Immunofixation was IgG (26 -kappa and 12 –lamdba) and IgA (6 –kappa and 6 -lambda). All patients were symptomatic at diagnosis. Sera samples (n=312) were analyzed for sFLC-kappa and sFLC-lambda with Freelite™ and sFLCR were calculated, and for IgGkappa, IgGlambda IgAkappa, IgAlambda with Hevylite™ and ratios IgGkappa/IgGlambda, IgGlambda/IgGkappa, IgAkappa,/IgAlambda and IgAlambda/IgAkappa (HLCRs) were calculated. sFLCRs and HLCRs values above the 95%-ile of normal individuals were considered abnormal. Statistical analysis was performed using SPSS ver 15.0. File data were reviewed.

At diagnosis sFLCR was abnormal in 86% of patients while HLCR was abnormal in all. All treatment lines were initiated according to standard criteria and median lines of therapy were 2 (range 1–11). Median follow up was 33 months (7–145). During patients' cumulative follow-up, 145 lines of therapy were studied and the subsequent responses were estimated. Thirty eight percent of responses were sCR, CR and nCR, 20% PR, 18% MR and 24% refractory and progressive disease. HLCR normalized in 44% of patients with sCR, CR and nCR. The depth of response correlated to PFS and patients in sCR, CR and nCR had longer PFS than the others (p<0.001). Serum FLCR and HLCR normal values at response were both strong parameters of increased PFS after treatment at any line (p=0.035 and p=0.046 respectively).

Serum HLCR normalization at plateau reflects prolonged responses in intact Ig MM.

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