Molecular Remission After VTD or TAD As Induction for Multiple Myeloma: Results with Two Different Methods of Analysis.

Abstract 2929

The high rate of complete response (CR) effected by novel agents as induction has also renewed interest in the evaluation of minimal residual disease (MRD) in Multiple Mieloma (MM) [1]. For this purpose, In our hospital we conducted a retrospective study to compare the activity of VTD induction versus TAD. Using two different methods, as flow cytometric (FC) assay and polymerase chain reaction (PCR) technology we evaluated in the bone marrow the molecular residual disease (MRD), in the subgroup of patients that obtained CR.

We evaluated 87 multiple myeloma patients treated between February 2009 and April 2012 and eligible for autologous transplant. Patients (table I) had untreated, newly diagnosed and symptomatic MM. All patients provided written informed consent. Patients were treated with 4 cycles of TAD or VTD. TAD consisted of four cycles of intravenous doxorubicin on day 1 every 28 days in day-hospital, dexamethasone 40 mg orally on days 1 through 4 and 9 through 12, and thalidomide 100 mg/day continuously and orally administered. VTD consisted of four 3-week cycles of bortezomib 1.3 mg/m²administered intravenously on days 1, 4, 8, and 11 plus dexamethasone 40 mg days 1–2 and days 3–4, 8–9, 11–12 (all cycles) and thalidomide 100 mg/day continuously and orally administered. Our target was the evaluation of minimal residual disease (MRD) in patients that obtained CR. Immunophenotyping was carried out by a FacsCanto II cytometer equipped with 3 lasers (405, 488, 633 nm). A seven-color method was used, with monoclonal antibodies (MoAb) conjugated with the following fluorochromes: FITC, PE, PercCP-Cy5.5, Pe-Cy.7, APC, APC-Cy.7, AmCyan [2].

PCR analyses were performed on mononuclear cells separated by Ficoll/Hypaque gradient. High molecular weight DNA was extracted and suitable aliquots were utilized for PCR assays to identify BM infiltration represented by clonal IgH rearrangement. Capillary electrophoresis and fluorescence detection with a virtual filter C was performed using a ABI Prism 310 Genetic Analyzer (Applied Biosystems). Runs were executed with the module GS STR POP 4 (1 ml) C with 10-second and 15 kV injection and run voltage, 60°C constant temperature, 24 min run time, using polymer POP 4 and the running buffer Genetic analyzer 1X (Applied Biosystem). Genescan 2.1 software was then used to analyze the PCR products, with accurate sizing and quantification of the peak areas, according to our previously published method [3]. After 4 cycles, The overall response rate was 91% in the VTD group versus 84% in the TAD group (Table 2). However, the CR plus VGPR rate was significantly higher in the VTD arm (51% vs 18%, P= .001). The difference in CR rate was 28% (30% in VTD group vs 2% in TAD group). In the only patient that obtained CR in the TAD group FC and PCR were able to still detect MRD but in ten of thirteen (77%) patients that achieved CR in VTD group both additional assays confirmed absence of MRD. VTD regimen was able to induce a very high rate of CR including undetected MRD even if evaluated with two different methods. In conclusion, in comparison with TAD induction, VTD significantly increased the rate of molecular remissions.