Low Dose Ara-C Versus Low Dose Ara-C and Arsenic Trioxide: the UK NCRI AML16 “Pick a Winner” Comparison.

A significant proportion of older patients with AML are not treated with conventional intensive chemotherapy [1] because they are unfit or not considered likely to benefit from an intensive treatment approach. Their outcomes are poor. Such patients have typically been treated with low-dose Ara-C (LDAC) or best supportive care (BSC) with hydroxyurea, and unrandomised studies of new agents have been used in this population. A recent randomised trial has shown that LDAC is superior to BSC in these patients [2]. Randomised trials are underway to assess the value of other novel treatments compared to LDAC. In an unrandomised phase 2 trial in 64 patients, Roboz et al found encouraging results using the combination of Arsenic Trioxide and LDAC. [3].

The UK NCRI AML16 trial is a programme of development which aims to test novel agents or combinations in untreated older patients with AML or high risk MDS (marrow blasts >10%) following a “pick a winner” design. The intention is to identify a “winner” which will produce a remission rate in excess of 30%, compared with 15-20% with LDAC. Using LDAC as the standard arm,the design allows unpromising treatments to be identified early (typically after 50 patients per arm), so that only those arms which show promise will continue to a trial with OS and DFS as endpoints.

We report our experience of LD Ara-C (20mg bd days 1-10 for 4 courses) versus LDAC combined with Arsenic Trioxide (ATO, 0.25 mg/kg d1-5, d9, d11 for 4 courses at 6-8 week intervals).

Between December 2006 and until its conclusion in May 2009, 166 patients were randomised, 84 to LDAC plus ATO, 82 to LDAC. The median age was 74 years; 80% of patients were aged over 70 years, 62% were male. There were no differences between the treatment arms with respect to age distribution, gender, performance status, de novo/secondary AML, high risk MDS, presenting WBC or cytogenetic risk group. Follow-up is complete to 1^st January 2009, with median follow up for survivors of 8 months (range 0.1-17), at which point 122 patients had been recruited, and there were a total of 60 deaths (LDAC n=25; LDAC+ ATO, n=35). CR status is known on 113 patients. Overall, 24 patients have entered CR/CRi (LDAC n=13, LDAC+ATO n=11) with 8 relapses (2 vs 6; 1 vs 3 patients have died following relapse).

The causes of death (60) were:-

The DMEC recommended closure of the LDAC + ATO arm of the trial because follow-up data on the first 50 patients per arm showed that ATO had failed to provide the 2.5% improvement in CR/CRi required for continued recruitment and that the required improvement in remission was unlikely with LDAC + ATO.

While ATO has a definite role in treating patients with APL, and may be of benefit in combination with other drugs in AML, the combination of LDAC + ATO in this patient population was not beneficial.

[1] Juliusson G et al. Blood 2009; 113: 4179—4187

[2] Burnett et al. Cancer 2007 109: 1114—1124

[3] Roboz Gail J et al. Cancer 2008;113(9):2504—11.

Off Label Use: Arsenic Trioxide is not licensed in this indication.