Combination of Bortezomib and Dexamethasone (VD) or Bortezomib, Adriamycine and Dexamethasone (PAD) Followed by High Dose Therapy and Peripheral Blood Stem Cell Transplantation in First-Line Treatment of T(4;14) Multiple Myeloma : a Prospective Study of the MAG Group.

Abstract 3408

Poster Board III-296

The t(4;14)(p16.3;q32), leading to the ectopic expression of two potential oncogenes, the Multiple Myeloma Set Gene (MMSET) and the Fibroblast Growth Factor 3 (FGFR3), is found in 15% of patients with multiple myeloma (MM) and is associated with a very poor prognosis. We previously shown in patients under 65 years of age that High Dose Therapy followed by Peripheral Blood Stem Cell Transplantation (HDT-PBSCT) provides a high response rate (RR) but a very short median relapse-free survival of only 11 months. In addition, relapses are often aggressive and chemoresistant. Thus, more effective regimen is urgently needed. We prospectively studied 23 t(4;14) MM patients treated with 3 or 4 cycles of a combination of Bortezomib and Dexamethasone (VD) (n=4) or of Bortezomib, Adriamycine and Dexamethasone (PAD) (n=19) as induction treatment before HDT-PBSCT (Melphalan 200 mg/m²). T(4;14) was detected using real time quantitative PCR searching for IGH/MMSET and FGFR3 transcripts. RR, event-free survival (EFS) and overall survival (OS) were evaluated. Median age at diagnosis was 51 years (range, 33-64). Isotype was IgA in 12 (52%) patients. All patients had stage II or III MM. An elevated serum β2m level (>3.5 mg/L) was found in 14 (61%) patients, and a low haemoglobin (Hb) level (<10 g/dL) in 10. Four presented with renal failure and 5 with hypercalcemia. Three (16%) of 19 patients had a t(4;14) without expression of FGFR3. After induction treatment with VD or PAD, PBSC were successfully harvested with granulocyte-colony stimulating factor only (n=15) or following a cycle of high-dose cyclophosphamide (n= 7). RR after induction treatment was complete response (CR) in 6 (26%) patients, very good partial response (VGPR) in 9 (39%), partial response (PR) in 3. Five patients had refractory or progressive disease (PD), including 1 who died before stem cell mobilization. RR after HDT was CR in 11 (48%), VGPR in 4 (17%) and PR in 4 (overall RR of 82%). Three had PD. With a median follow-up of 18 months (range, 3-32), 9 (39%) patients are alive without relapse, including 4 with a 19, 27, 30 and 32 months follow-up respectively. Twelve (52%) patients relapsed. Two patients died in the first month post HDT from PD. We found a median EFS and OS from initiation of therapy of 14.7 and 30.9 months respectively. EFS was not influenced by Hb and/or serum β2m level. However, we found a significantly longer OS in patients with low β2m (median non reached) as compared to patients with high β2m (median=23.1 months, p=0.04). These preliminary results illustrate the heterogeneity of this disease and indicate that some t(4;14) MM patients seem to benefit from bortezomib containing regimen as induction treatment before HDT in term of EFS and OS. A larger series with a longer median time of follow up will be presented.