PROSPECTIVE PHASE II STUDY ON LOW-DOSE 5-AZACYTIDINE FOR TREATMENT OF SYMPTOMATIC PATIENTS WITH LOW/INT-1 RISK MYELODISPLASIA

Background. Aberrant DNA-methylation in the CpG sites of several tumor suppressor genes is considered the dominant pathogenetic mechanism in MDSs and the main cause of progression to AML. The use of hypomethylating agents significantly modified the therapeutic approach to MDS patients, primarily in higher-risk MDS patients. In lower-risk MDSs the use of 5-AZA hypomethylating agent is less understood. Aims. We prospectively evaluated the efficacy and safety of 5-AZA low-dose in Low or Int-1 risk MDS patients who were symptomatic and/or unresponsive to previous treatments. Furthermore, we studied the genetic profile by single nucleotide polymorphism (SNP) arrays and the molecular effects of 5-AZA on PI-PLCbeta1 promoter methylation, in order to identify these biological factors possibly correlated with the response to 5- AZA. Methods. 5-AZA was administered at a dose of 75 mg/mq/daily s.c for 5 consecutive days every 28 days for a total of 8 cycles. Final response was checked at the end of the 8th course. SNP microarray analysis was performed from mononuclear cells isolated from bone marrow aspirate samples before treatment. PIPLC beta1 gene expression was evaluated on peripheral blood samples from patients at baseline, and monthly until the 8th cycle of 5-AZA administration. Results. Between September 2008 and February 2010, 32 MDS patients with IPSS risk Low- or Int-1 were enrolled into the study. Most patients had a normal karyotype (63%) by metaphase cytogenetics, were BRC transfusion-dependent (81%), receiving a median of 4 units/mo, and were previously unresponsive to treatment including ESAs (69%). Twenty-six patients (81%) completed the treatment plan (8 cycles). The Overall Response Rate after the 8th cycle was 58% (15/26 pts) whereas 42% of patients maintained a stable disease; no patient progressed towards a high-risk MDS or AML. Five (19%) patients reached a complete remission whereas 10 (38%) achieved an hematological improvement. Transfusion independent was achieved in 8/26 patients (31%). The median duration of the response was 10 months; five patients maintain their response, that is CR in 2 cases (+24 and +30 months) and HI-E in 3 cases (+14, +25,+26 months) without any treatment or supportive therapy. All but one patients (14/15) who achieved an hematologic response during treatment with 5-AZA showed a statistically significant increase in PI-PLCbeta1 mRNA expression. In all patients the increase of PI-PLCbeta1 levels anticipated the clinical response obtained at the 8th cycle. SNP array karyotyping identified genomic abnormalities in all analyzed patients (100%) compared with only 9/26 (35%) with metaphase cytogenetics; although, SNP array-based assay has been demonstrated to enable the identification of genetic abnormalities in all analyzed patients, the type and the number of copy number abnormalities were not correlated with clinical response to 5-Aza. By contrast, LOH alterations showed to have a trend with stable disease. Conclusions. The current results of our study showed that 5-Aza low-dose schedule may be a safety and effective treatment for low risk MDS pts and may induce durable responsesThe correlation between the hematologic response and the PI-PLC1 expression indicate that PI-PLC1 may be a realiable marker of response to AZA.