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Background: CD20 antigen down-modulation by anti-CD20 rituximab treatment is a well-recognized phenomenon in patients with non-Hodgkin's lymphoma. However, few data are currently available on this topic in other lymphoproliferative disorders, in particular in chronic lymphocytic leukemia (CLL). Objective: The aim of this study was to establish how many patients with CLL show a disappearance of CD20 antigen after salvage treatment with rituximab and its possible clinical significance. Methods: We sequentially analyzed CD20 expression by flow cytometry in patients treated with rituximab in combination with other agents for relapsed/resistant disease. Results: Eleven white patients with CLL (6 females, 5 males; median age, 71.6 years [range, 60–84 years]) were included in the study. Three of the 11 patients were not positive for CD20 due to complete response at baseline. Four of the remaining 8 patients (50%) lacked CD20 antigen on neoplastic cells after monoclonal antibody treatment. Two of them developed Richter's syndrome and died within 4 months. The phenomenon was transient in the other 2 patients, who were alive after a follow-up of 25 and 26 months, respectively, with CD20-positive recurrent disease. Conclusions: In this study, CD20 antigen disappearance in patients with CLL treated with rituximab-containing salvage regimens occurred in 4 of 8 (50%) tested patients, half of whom developed Richter's syndrome. [Note: Since the initial writing and submission, a third patient developed Richter's syndrome.] In 2 patients (50%), CD20 returned at progression.

This was a retrospective, comparative study focused on the extended follow-up of 192 transfusion-dependent patients with myelodysplastic syndromes treated (n. 83) or not treated (n. 109) with recombinant erythropoietin alpha (r-EPO) as single agent during the course of their disease. The results supported the safety of this treatment in the long term and also showed a significant survival advantage (median 52 months vs. 31 months, p < 0.0095) in responding patients as compared to non-responding ones or to subjects never treated with r-EPO. At multivariate analysis, response to r-EPO maintained an independent prognostic value on OS.

The development of multiple myeloma (MM) bone disease is mediated by increased number and activity of osteoclasts (OCs). Using an in vitro osteoclastogenesis model consisting of unstimulated and unfractionated peripheral blood mononuclear cells (PBMCs) from patients with MM, we showed that T cells support the formation of OCs with longer survival. Different from T-cell–depleted MM PBMC cultures, exogenous macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor-κB ligand (RANKL) were necessary for the formation of OCs; however, they did not exhibit longer survival. We found up-regulated production of RANKL, osteoprotegerin (OPG), and TNF-related apoptosis-inducing ligand (TRAIL) by fresh MM T cells. Despite high OPG levels, the persistence of osteoclastogenesis can be related to the formation of the OPG/TRAIL complex demonstrated by immunoprecipitation experiments and the addition of anti-TRAIL antibody which decreases OC formation. OCs overexpressed TRAIL decoy receptor DcR2 in the presence of MM T cells and death receptor DR4 in T-cell–depleted cultures. In addition, increased Bcl-2/Bax (B-cell lymphoma-2/Bcl2-associated protein X) ratio, following Bcl-2 up-regulation, was detected in OCs generated in the presence of T cells. Our results highlight that MM T cells support OC formation and survival, possibly involving OPG/TRAIL interaction and unbalanced OC expression of TRAIL death and decoy receptors.

Abstract 729 Introduction: The prognosis of primary plasma cell leukemia (PPCL) remains poor. The “novel agents” have recently shown promising results in PPCL patients in case reports or small retrospective series. Here we describe the first prospective, multicenter, phase II clinical trial of PPCL, where lenalidomide in combination with low dose dexamethasone (Ld) was tested as initial therapy in newly diagnosed patients fulfilling the IMWG diagnostic criteria of PPCL. Patients and methods: Ld regimen consisted of lenalidomide 25 mg/d for 21 days and oral dexamethasone 40 mg on days 1, 8, 15, and 22 for each 28-day cycle. After 4 cycles, responding patients not eligible for stem cell transplantation (SCT) continued until 8 cycles of full-dose Ld, followed by a maintenance dose of single agent lenalidomide equal to 10 mg/d on days 1–21 of each 28-day cycle. Patients responding after 4 cycles and eligible for SCT proceeded according to the treatment centre's transplant policy. Patients not responding after 4 cycles or progressing during this treatment were considered off-study. Appropriate dose reductions (in particular for patients with reduced renal function at baseline), double contraception methods and anti-thrombotic/anti-infective prophylaxis were recommended. The primary end-point was early response rate according to IMWG uniform response criteria. Secondary end-points were PFS, OS, feasibility and efficacy of SCT, safety. Results: According to the Simon optimal two-stage adaptive design, twenty-three patients were enrolled in between March 2009 and May 2011. The male/female ratio was 1.1, and median age was 60 years (range 44–80). The median absolute number and percentage of circulating plasma cells were 4.280/μl (range 1.500–114.660) and 34% (range 21–90) respectively. Fifteen patients (65.2%) had abnormal renal function at presentation. Twenty-one patients (91.3%) were tested by FISH analysis and cytogenetic abnormalities were detected in all of them, del13q being the most frequently found (16 patients). Seventeen patients showed multiple chromosomal lesions. Involvement of chromosome 14 was observed in 18 patients, three of whom showed t(4;14). Chromosome 1q gain and del17p were detected in 10 and 7 patients, respectively. In the intention-to-treat (ITT) population, overall response rate (ORR) after at least one Ld cycle was 73.9% (17/23), with 8 patients (34.7%) achieving partial remission (PR), 5 (21.7%) very good PR (VGPR), 3 (13%) complete response (CR), and 1(4.3%) near CR (nCR) (VGPR or better: 39%). In the efficacy-evaluable (EE) population, 14 out of 15 patients who received the initially planned 4 Ld cycles (65.2% of the ITT population) responded (ORR 93.3%), achieving 5 PR (33.3%), 5 VGPR (33.3%), 1 near-CR (6.6%) and 3 CR (20%) (VGPR or better: 59.9%). The maintenance phase was reached and safely performed in 4 responding patients not eligible for SCT, 3 of whom relapsed after 2, 8 and 22 months, respectively. After Ld induction therapy, 8 patients received single (n. 4) or double (n. 4) autologous SCT (ASCT); another patient underwent a sequence of ASCT followed by non-myeloablative allogeneic SCT (AlloSCT). Six eligible patients did not receive ASCT frontline, due to initial Ld failure or adverse events; three of them underwent single ASCT (n. 2) or tandem ASCT/non-myeloablative AlloSCT (n. 1) after a bortezomib-based salvage therapy, achieving 2 CR and 1 PR. After a median follow-up of 23 months, median OS and PFS in ITT population were not reached and 22 months, respectively. All transplanted patients remained alive, although three of them relapsed and started salvage treatments; OS was 12 months in the 11 patients who did not receive ASCT (p < 0.001). The correspondent figures for PFS were 29 and 16 months, respectively (p < 0.01). Considering ITT population, multivariate analyses showed that SCT was positively correlated to both OS and PFS. There were 17 episodes of grade 3/4 non hematological toxicity, which occurred in 13 patients (5 infections, 3 renal, 3 metabolic, 2 gastro-intestinal, 2 skin, 1 fatigue, 1 thromboembolic), causing early interruption of Ld treatment in 4 patients. Grade 3/4 hematological toxicity (mainly neutropenia) occurred in 11 patients (47.8%). Conclusions: Ld may be a feasible and effective initial therapeutic option for PPCL, particularly in patients who receive ASCT after a short course of induction treatment. Disclosures: Musto: Celgene: Honoraria, Research Funding. Off Label Use: Lenalidomide as first line therapy of plasma cell leukemia. Petrucci:Celgene: Honoraria. Cascavilla:Celgene: Honoraria. Di Raimondo:Celgene: Honoraria. Caravita:Celgene: Honoraria. Morabito:Celgene: Honoraria. Offidani:Celgene: Honoraria. Bringhen:Celgene: Honoraria. Boccadoro:Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Palumbo:Celgene: Consultancy, Honoraria.

Abstract 2925 Primary plasma cell leukemia (PPCL) is an aggressive variant of multiple myeloma, accounting for 0.5–4% of all newly diagnosed myeloma cases and characterized by a short survival (generally less than 1 year), which is only moderately improved by transplant procedures. Novel agents seem to be able to ameliorate the poor clinical outcome of both primary and secondary leukemic phases of myeloma; however, no data are currently available on the use of lenalidomide as first line therapy in PPCL. On March, 2009, we started a multicenter, phase II trial aiming to evaluate safety and antitumor activity of lenalidomide in combination with dexamethasone (LD) in previously untreated PPCL. Here we report the final results of this study. Newly diagnosed PPCL patients received lenalidomide at a dose of 25 mg/d for 21 days and oral dexamethasone at a dose of 40 mg on days 1, 8, 15, and 22 for each 28-day cycle. After 4 cycles, responding patients not eligible for stem cell transplantation (SCT) continued until 8 cycles of full-dose LD, if tolerated, followed by a maintenance dose of single agent lenalidomide equal to 10 mg/d on days 1–21 of each 28-day cycle. Patients responding after 4 cycles and eligible for SCT proceeded according to single Centre transplant policy. Patients not responding after 4 cycles or progressing during this treatment were considered off-study. The primary endpoint was early response rate according to International Uniform Criteria. The secondary endpoints were PFS, OS, safety and percentage of eligible patients able to undergo autologous or allogeneic SCT. Appropriate dose reductions, contraception methods and anti-thrombotic prophylaxis were applied. Twenty-three patients, as requested by the Simon Optimal Two-Stage Adaptive Design adopted, were enrolled. The trial was therefore closed on May, 31, 2011. M/F ratio was 0.7, mean age was 62 years (range 44–80). Circulating plasma cells ranged from 2.1 to 115 × 10e9/l. Moderate renal failure, increased LDH and extramedullary disease occurred in 39.1%, 43.5% and 13 % of patients, respectively. Hb was < 10 g/dl in 19 patients (82.6%), while platelet count was < 50 × 10e9/l in 5 patients (21.7%). Karyotype abnormalities were detected by FISH in 21 out of 22 tested patients; in particular, 1p loss was found in 9 patients, 1q gain in 10 patients, del(13q) in 16 patients, del(17p13) in 7 patients, t(11;14) in 7 patients, t(4;14) in 3 patients and MAF translocations, including t(14;20) and t(14;16), in 8 patients. Seventeen patients had a combination of two (n. 5) or more (n. 12) cytogenetic lesions. On intention-to-treat analysis, 14 patients completed the initial four planned cycles and all of them responded. In particular, 6 PR (26.1%), 4 VGPR (17.4%), 1 near-CR (4.3%) and 3 CR (13%) were achieved (ORR 60.8%, VGPR or better 34.7%). Causes of early treatment discontinuation were: a) progressive disease (4 patients, after an initial, brief response in 2 cases); b) severe adverse events (4 patients: one acute renal failure, one Stevens-Johnson's syndrome, one pneumonia suspected for Pneumocystis carinii etiology, one multi-organ failure); c) death in PR due to causes unrelated to treatment or disease (one patient). Other relevant non-hematological toxicities included four episodes of pneumonia and one case of DVT. Grade 3–4 hematological toxicities occurred in about half of cases, requiring Lenalidomide dose adjustments. So far, among subjects achieving a response after 4 LD cycles, 8 eligible patients have successfully collected peripheral blood stem cells: 5 of them have completed single or double autologous SCT, one patient received tandem autologous-allogeneic non myeloablative SCT from a MUD donor. All patients transplanted after LD are currently alive and in remission phase. The maintenance phase has been reached in 3 responding patients not eligible for SCT, 2 of whom have relapsed after 2 and 8 months, respectively. With a mean follow-up of 15 months, OS and PFS are 65.2% and 52.1%, respectively. LD is a possible initial therapeutic option for PPCL, particularly in patients who receive SCT after a short course of induction treatment. Caution is required to prevent and to manage renal and hematological toxicities, as well as infectious complications. Considering some previous results obtained with other novel agents, the combination of lenalidomide and bortezomib might be an appealing approach to investigate prospectively in PPCL patients. Disclosures: Musto: Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Petrucci:Celgene: Honoraria. Cascavilla:Celgene: Honoraria. Di Raimondo:Celgene: Honoraria. Caravita:Celgene: Honoraria. Morabito:Celgene: Honoraria. Offidani:Celgene: Honoraria. Bringhen:Celgene: Honoraria. Boccadoro:Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Palumbo:Celgene: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau.

Abstract 4951 Background Primary Plasma Cell Leukemia (PPCL) is an aggressive, rare variant of multiple myeloma, with clinical, molecular and phenotypic peculiarities, which accounts approximately for 2% to 4% of all myeloma diagnoses. The prognosis of PPCL patients is usually poor, with less than half of patients responding to conventional chemotherapy and a median survival of 7 months. Even by using autologous or allogeneic transplant procedures, survival generally does not exceed three years. Bortezomib has recently provided some promising results in this setting, but, given all the above, new treatments for PPCL are greatly awaited. Lenalidomide is a new immunomodulating agent with great efficacy in multiple myeloma, especially when associated with dexamethasone or other drugs. There are, indeed, some sporadic case reports of PPCL patients treated with lenalidomide as salvage therapy, but no data are currently available on the use of this drug as first line therapy in this disease. Patients and Methods On March, 2009, we started an open label, prospective, multicenter, exploratory, single arm, two-stage study aiming to evaluate safety and antitumor activity of the lenalidomide/low dose dexamethasone combination (Rd), as first line therapy in patients with PPCL. The primary endpoint was early response rate according to International Uniform Criteria. The secondary endpoints were TTP, PFS, OS, percentage of eligible PPCL patients able to collect peripheral blood stem cells and to undergo autologous or allogeneic stem cells transplantation after Rd, serious and severe adverse event rate. According to this study protocol, all eligible, newly diagnosed adult patients with PPCL receive Lenalidomide at a dose of 25 mg daily for 21 days every 28 days. Oral dexamethasone is administered at a dose of 40 mg daily on days 1, 8, 15, and 22 for each 28-day cycle. After 4 cycles, patients who achieve at least PR and not eligible for autologous or allogeneic stem cell transplantation, continue with Rd until clinically appropriate (disease progression, unacceptable toxicity, patient's decision to leave the protocol). In these patients, a maintenance dose of lenalidomide alone equal to 10 mg/die days 1-21 every month is considered after at least 8 full dose Rd cycles. Patients responding after 4 Rd cycles and eligible for transplant procedures, proceed according to single Centre transplant policy. Patients not responding after 4 cycles or progressing under Rd treatment are considered off-study. Appropriate contraception methods and anti-thrombotic prophylaxis are planned. Results Four enrolled patients (1 male, 3 female, mean age 65 years, range 58-69) are currently evaluable for early response. All had unfavourable cytogenetics, including del13, t(4;14), t (14;16), or a complex karyotype. Circulating plasma cells ranged from 4.4 to 9.2 ×10e9/l. One patient had at baseline a moderate degree of renal failure (serum creatinine levels 2 mg/dl). After at least 2 Rd cycles (range 2-4), two PR and two VGPR were achieved (overall response rate 100%), with disappearance or near complete reduction of circulating plasma cells in all cases. The most relevant toxicities were grade 3 neutropenia and pneumonia, occurring in one patient and resolved by appropriate lenalidomide dose reduction, introduction of G-CSF and antibiotic therapy. One patient died in PR, due to causes unrelated to PPCL or treatment. As, according to the Simon, two-stage design adopted, more than two responses occurred within the first ten patients enrolled (stage 1), a total of 22 PPCL subjects will be accrued to complete the stage 2 of the trial. Conclusions These findings, though very preliminary, suggest that the combination of lenalidomide and dexamethasone may be a safe and promising initial therapy for PPCL patients, which can rapidly control the disease and could permit to perform following single patient-adapted therapeutic strategies. An update of this study, including molecular data, a larger number of patients and a longer follow-up, will be presented at the Meeting. Disclosures Musto: Janssen-Cilag: Honoraria; Celgene: Honoraria, Research Funding. Off Label Use: Lenalidomide is approved in Italy for advanced multiple myeloma, not for plasma cell leukemia. This is a clinical trial registered at AIFA (Italian regulatory Agency for Drugs), EudraCT No. 2008-003246 28. Petrucci:Janssen-Cilag: Honoraria; Celgene: Honoraria. Morabito:Celgene: Honoraria; Janssen-Cilag: Honoraria. Cavo:Celgene: Honoraria; Janssen-Cilag: Honoraria. Boccadoro:Celgene: Honoraria; Janssen-Cilag: Honoraria. Palumbo:Celgene: Honoraria; Janssen-Cilag: Honoraria.

Plasma cell leukemia (PCL) is an aggressive, rare variant of multiple myeloma (MM), with peculiar clinical and biological characteristics, which represents about 2–4% of all MM. PCL exists in two forms: primary PCL (about 60% of cases) presents “de novo”, without previous evidence of MM; secondary PCL, which accounts for the remaining 40%, consists of a leukemic transformation occurring in about 1% of patients with a previously diagnosed MM. We have recently shown that bortezomib is an effective agent for the treatment of both primary and secondary PCL, mainly in the setting of pre-treated disease (Musto et al, Cancer 2007). In the present study we conducted a multicenter retrospective survey focused on unselected patients with a diagnosis of primary PCL who had received bortezomib exclusively as first line therapy for the treatment of their disease, outside of clinical trials. To-date, 15 patients, diagnosed according to International Myeloma Working Group criteria, have been collected, 12 of whom (seven male and five female, 49 to 77 year-old) have been so far evaluated for response. Circulating plasma cells ranged from 3 to 95 × 10e9/L. Seven patients had an IgG M-component, two had IgA, two light chains, while one patient was not secretory. Five patients had concomitant extramedullary disease. Unfavourable cytogenetic abnormalities were observed in 4 out of 7 patients with available karyotype. Bortezomib was generally given using the standard schedule of 1.3 mg/sqm days 1, 4, 8, 11, with an interval of 10 days between cycles. Minor modifications were performed, according to tolerance. Three patients received dexamethasone (VD), two dexamethasone and thalidomide (VTD), six doxorubicin and dexamethasone (PAD), and one oral melphalan and prednisone (MPV) in combination with bortezomib, for 2–6 cycles. Three patients underwent autologous, two allogeneic and one a sequence of autologous followed by non-myeloablative allogeneic stem cell transplantation after induction therapy. One out of five eligible patients failed to collect peripheral blood stem cells. Grade 3–4 hematological, neurological, infectious and renal toxicities occurred in 6, 2, 1 and 1 patient, respectively. Other toxicities (diarrhoea, nausea, skin rash) never reached grade 3. According to the International Uniform Response Criteria, 4 partial remissions (reduction of M-component > 50%), 5 very good partial remissions (reduction of M-component > 90%, with positive immunofixation), and 3 complete remissions (negative immunofixation) were achieved (100% overall response). In all patients circulating plasma cells disappeared. One patient with pre-existing renal damage died of progressive disease after 3 months, developing more severe renal failure. Another patient died in CR 6 months after diagnosis, while performing allogeneic stem cell transplantation. Three patients relapsed after 5–8 months and 2 of them died with progressive disease within 4 months from relapse. The remaining 8 patients are alive, and 6 of them maintain their remission phase after 9 to 19 months. One-year progression-free survival and overall survival were 50% and 66.6%, respectively. Primary PCL is usually characterized by poor prognosis. Global response rate to standard chemotherapy is less than 50% and median survival is only 7 months. Stem cell transplantation may be more effective in some, but not all cases. Our findings suggest that, in these patients, the front-line use of bortezomib induces a very high rate of good quality responses, whose duration, however, may be short. This suggests that, in primary PCL, bortezomib should be integrated within more intensive therapeutic programs, including other active drugs and, when possible, stem cell transplantation.