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The present retrospective analysis evaluated the efficacy and safety of the VTD (bortezomib, thalidomide, dexamethasone) regimen in 205 newly-diagnosed patients with multiple myeloma (MM) eligible for high dose therapy and autologous stem cell transplantation (HDT/ASCT) in routine clinical practice. With a median of 6 cycles (range, 1–8), at least partial response was achieved in 94.6% and at least very good partial response (VGPR) was achieved in 67.8% of patients. Peripheral neuropathy (PN) grade 2–4 was observed in 28.7% of patients. In 72% of patients undergoing stem cell mobilization one apheresis allowed the number of stem cells sufficient for transplantation to be obtained. Following HDT/ASCT the sCR rate increased from 4.9 to 14.4% and CR from 27.8 to 35.6%. The results demonstrated that VTD as an induction regimen was highly efficient in transplant eligible patients with MM with increased at least VGPR rate following prolonged treatment (≥6 cycles). Therapy exhibited no negative impact on stem cell collection, neutrophils and platelets engraftment following ASCT. Therapy was generally well tolerated and PN was the most common reason of dose reduction or treatment discontinuation.

Studies exploring the significance of minimal residual disease (MRD) in plasma cell myeloma (PCM) have proven its prognostic value, regardless of the type of administered treatment. In order to assess the current practice for evaluating MRD in Poland, we conducted a survey on the methods for assessing MRD and on the MRD testing time points at Polish hematological centres. Seven out of 15 institutions surveyed use of the flow cytometry (FC) method for MRD assessment. The FC-MRD assessment is performed uniformly only in those patients achieving complete remission (CR). However, the specific indications and assessment time points differed at the tested centres including: testing MRD only after autologous hematopoietic stem cell transplantation (auto-HSCT), after auto-HSCT and consolidation, after completion of first line chemotherapy or after obtaining CR in any line of treatment. The study also showed considerable heterogeneity in the FC-MRD methodology, which affects test sensitivity (from 10–3 to 10–5). None of the surveyed centres uses molecular techniques for MRD assessment. In 8 of the 15 institutions, patients are monitored by imaging techniques. Our survey may thus be useful for developing guidelines and standardization of MRD assessment in PCM in Poland.

Abstract 4097 A small subset of patients with hypereosinophilic syndrome (HES) presents an interstitial deletion in chromosome 4q12, which leads to the expression of an imatinib -responsive fusion gene- called FIP1L1-PDGFRA (F/P). These patients have chronic eosinophilic leukemia (CEL). Here, we treated twenty five F/P-positive CEL patients (22 male, 2 female; median age of 50 years) with imatinib using initial daily doses ranging from 100 – 400 mg. At diagnosis a median peripheral blood eosinophilia and eosinophil marrow infiltration were 12×109/L (range 2.5–40.8) and 39% (range 7–80), respectively. Splenomagaly was the most frequent clinical manifestation in this patient subgroup. All imatinib-treated patients achieved clinical and molecular response. A complete haematological remission (CHR) was demonstrated after median of 13 days (range 3–90) whereas molecular response (MR) was confirmed after median of 9 months (range 3–24). In a remission maintenance phase, imatinib doses were de-escalated and they were following: 100mg once weekly (n=11), 100mg twice weekly (n=6), 100mg daily (n=5), 200mg once weekly (n=2) and 400mg once weekly (n=1). Plasma imatinib level was measured 24 hours after the last drug intake in 7 patients treated in once weekly schedule and it remained extremely low, ranging between 44–167 ng/ml. Molecular studies performed at the same time points confirmed molecular remission. With a median follow-up of 40 months all patients remained in CHR and FIP1L1-PDGFRA expression was undetectable in all treated patients. These data indicate that even very low imatinib doses are highly effective in remission maintenance of patients with F/P-positive CEL. Disclosures: No relevant conflicts of interest to declare.