CLAG-Based Chemotherapy in Previously Untreated AML Patients: 12 Year Follow-up

Introduction:

The 7+3 combination of cytarabine plus an anthracycline is the most commonly used induction regimen for AML in the US. There is evidence FLAG-IDA may be superior to 7+3 (Solh et al Leuk Res 2020), and that cladribine is superior to fludarabine (Holowiecki et al JCO 2012). Currently we report the results of CLAG-based chemotherapy in newly-diagnosed AML patients.

Methods: This single-center retrospective cohort studied all patients with newly-diagnosed AML who received CLAG-based induction therapy (with or without an anthracycline, depending on cardiac function) between February 2011 and June 2023. Chemotherapy consisted of cladribine 5 mg/m ² daily times 5 days, cytarabine 2 gm/m ² over 4 hrs daily times 5 days (given 2 hours after the completion of each cladribine dose), plus G-CSF 300 ug daily during chemotherapy and then based on weight after that. Patients with adequate cardiac function also received 3 days of mitoxantrone 12 mg/m ² (CLAG-M) or idarubicin 12 mg/m ² (CLAG-IDA) on days 1-3 or 2-4. Many of these patients were treated prior to the current era of targeted therapies and thus most received chemotherapy without targeted agents. Post-remission therapy was given at the physician's discretion based on the patient's tolerance of induction chemotherapy. Complete response (CR) was defined as less than 5% blasts in the marrow with recovery of ANC >1000/mm ³ and platelets >100,000/mm ³. Lesser responses included CRi, CRp and PR. All others were considered failures or early deaths (within 30 days). This study was approved by the IRB of New York Medical College.

Results: We analyzed all 87 newly-diagnosed AML patients that were treated with CLAG-based induction therapy (CLAG alone: 10%, CLAG-IDA: 87%, CLAG-M: 3%). 4 patients with a FLT-3 mutation received a FLT-3 inhibitor concurrently. Post-remission therapy included allo transplant (13%), further CLAG+/- IDA, reduced to 4+2 days (84%), HiDAC (27%), and hypomethylators (36%), in that order of priority. The intensity of the post-remission therapy was matched with the perceived ability of the patient to tolerate it. Many patients received more than one post-remission therapy in sequence. The median age of the cohort was 65 (33-85) years. 59% were male, 47% were smokers, 6% had prior MDS and 13% had therapy-related AML. The median baseline WBC was 9.7 (0.4-392) k/mm ³. 10% of patients were stratified as favorable ELN cytogenetic risk, 45% as intermediate, and 45% as adverse. TP53 mutation was present in 22% patients and FLT3 mutation in 14% patients.

CR was obtained in 67% of patients overall and did not differ significantly by age (<60: 65%, 60-70: 70%, >70: 64%). Early deaths (within 30 days) were more common in older patients (<60: 3%, 60-70: 3%, >70: 8%). The CR rate was similar across all cytogenetic risk groups (good risk: 67%, intermediate risk: 68%, poor risk: 62%) and was favorable in patients with a TP53 mutation (68%), as well as those with therapy-related AML (69%).

The median overall survival (OS) was 13 months. By cytogenetic risk the median OS was good: not reached, intermediate: 25.6 months and poor: 6.8 months (Figure 1). It should be noted that two patients with good risk cytogenetics who expired included an 80-year-old woman with therapy-related AML after treatment for breast cancer who declined further therapy after cycle 1 and survived 20 months with no further therapy, as well as a second unvaccinated patient who expired due to complications of COVID. Median OS by age was <60: 18 months, 60-70: 25.6 months and >70: 8 months (Figure 2). Median overall survival for patients with TP53 mutation was 5.6 months.

Conclusion: CLAG provides an alternative induction regimen to 7+3. Interestingly, in contrast to 7+3, CR rates did not differ significantly by age or cytogenetic risk group. The older patients treated on this trial were a select group that were considered eligible for intensive chemotherapy. Many of the patients on this trial would be treated differently today, with the availability of more targeted therapies. However the relatively high response rates in patient with poor risk cytogenetics and/or TP53 mutation gives fit patients the opportunity of pursuing stem cell transplantation.