Maintenance Treatment with 5-Azacitidine for Patients with High Risk Myelodysplastic Syndr–ome (MDS) or Acute Myeloid Leukemia Following MDS (MDS-AML) in Complete Remission (CR) after Induction Chemotherapy

Around 50% of patients with high-risk MDS or MDS-AML may enter CR after induction chemotherapy, but CR duration, as well as overall survival is usually short. To address this clinical problem the Nordic MDS Group designed a prospective multicenter phase II study, which assessed the clinical feasibility and utility of long-term maintenance treatment with azaciditine. Sixty patients with high-risk MDS (IPSS intermediate-2 or high) (n=23) or AML following a previous known MDS (n=37) were enrolled between 2004 and 2006. The mean age was 68 (54–83) and patients should not be eligible for stem cell transplantation. Induction treatment consisted of standard doses of daunorubicin and ara-C. Patients in CR received low dose azacitidine subcutaneously 5/28 days until relapse, unless unacceptable toxicity developed. Methylation status of the P15^ink4b (P15), E-cadherine (CDH) and Hypermethylated in Cancer 1 (HIC) gene was analysed at study start, in CR and in some patients during follow up. Last follow up was on August 1 2008, 24 months after the last CR was reported. Twenty-four patients (40%) reached CR and 23 of these started maintenance treatment with azacitidine. The initial dose of azacitidine was 75 mg/m² but as four of the first five enrolled patients developed grade 4 cytopenia, the starting dose was lowered to 60 mg/m², and was allowed to be reduced to 45 or 30 mg/m² to avoid severe cytopenias. The mean dose of azacitidine was 54.3 mg/m². Azacitidine was well tolerated. In 52% of the cases no side effects at all were reported. The most commonly reported side effect was mild rashes at the injection site (35%). Twenty-two percent developed fever or some kind of infection, mostly mild. Myelosuppression (grade 1–3) was seen in 22% of the cases. As previously reported, the probability of reaching CR was negatively correlated to promoter hypermethylation of CDH (p=0.008) and none of the 6 patients hypermethylated on all 3 genes reached CR (p=0.03) and hence only four patients hypermethylated on other genes than P15 received demethylating therapy. The median CR duration for the azacididine treated group was 13.5 months (2–49+) and median survival time from time of inclusion in the study for the same group was 20 months (4–52+). Four of 23 patients (17%) had a CR exceeding 24 months (32–52+). The two patients hypermethylated on CDH pre-induction had CR durations of only 2 and 5 months respectively. By last follow up 3 patients were still in CR. Of 10 patients without any methylation pre-treatment, all but one maintained this pattern in CR. Of the nine patients with pre treatment methylation of at least one gene, only one remained hypermethylated in CR. This patient had a CR duration of only 5 months. One patient showed development of P15 hypermethylation in the bone marrow sampled at 12 months and relapsed at 15 months. These findings support previous reports on P15 hypermethylation as a marker for minimal residual disease (MRD) and threatening relapse. In the whole group, survival was significantly shorter in patients with CDH methylation (3 vs 9 months, p=0.005), while pre-treatment p15 methylation status did not affect CR duration or overall survival. In conclusion, we show for the first time that maintenance treatment with azacytidine is feasible and associated with a median CR duration of 13.5 months, and very mild side effects. However azacytidine does not seem to prevent relapse in the majority of patients, including those with hypermethylation pre-treatment and/or in CR. Hypermethylation of multiple genes is a strong negative factor for survival, probability of CR, and CR duration. We observe a subset of patients, 17%, with a CR duration of >24 months; but no persistent pattern regarding cytogenetics, methylation or morphology could be identified in this group. The strong negative impact of E-Cadherin methylation, a gene involved in adhesion, warrants further investigation.