Delayed Cytogenetic Response and Reduced Rate of Major Molecular Response Associated to Increased Body Mass Index At Baseline in Chronic Phase Chronic Myeloid Leukemia Patients Treated with Imatinib.

Abstract 2784

Obesity, measured as body mass index (BMI), has been identified as a possible risk factor for the onset of several solid tumors as well as for chronic myeloid leukemia (CML). To date, no correlations have been reported in this latter disease between BMI at baseline and response to targeted therapies. We refer here on the impact of BMI on clinical response in CML.

Three hundred and thirty-nine chronic phase (CP) CML patients treated with imatinib entered the study: 142 patients first received interferon alpha outside clinical trials and were then switched to imatinib for failure. For this group of patients, BMI was collected at the time of start of imatinib. The remaining patients were consecutively treated with imatinib first-line from January 2000 onward. BMI was defined as the individual's body weight divided by the square of his of her height and patients were categorised according to WHO into four categories: underweight (BMI < 18.5), normal weight (BMI 18.5-< 25), overweight (BMI 25-<30) and obese (BMI ≥ 30). All patients were followed according to ELN guidelines. We also analysed 25 CP-CML patients treated frontline with nilotinib.

One hundred and fifty-six patients (46%) were categorized as underweight/normalweight, while 183 patients (54%) were classified as overweight/obese. BMI increased with age, with a median age of 29 years in underweight category, 43.4 years in normal weight, 54.9 years in overweight and 62.4 years in obese patients (p=0.001). We did not reveal statistically significant association between BMI and prognostic risk stratification at baseline, even when we used new EUTOS score, or type of BCR/ABL transcript. No statistically significant difference was revealed in terms of overall CCyR rate which was 87% for underweight/normal weight categories compared to 84% for overweight/obese group (p=0.34). If compared to patients with low BMI (< 18.5–25), patients with increased BMI (> 25–40) at diagnosis who received imatinib, showed a significantly longer median time to reach CCyR (6.8 months vs 3.3 months, p=0.01), a reduced rate of MMR (77% vs 58%, p=0.01) which was also achieved in a longer median time (29 months compared to 14 months, p=0.03). At 18 months, molecular kinetics revealed that median BCR-ABL/ABL ratio was 0.6% ^IS (range 0.001%-2%) in underweight/normal weight group compared to 1.6% ^IS (range 0.01%-3%) in overweight/obese category (p=0.01). Conversely, no differences were revealed with respect to BMI in patients treated frontline with nilotinib and also patients with increased BMI obtained rapidly CCyR and MMR, with an incidence similar to that of underweight/normal weight patients.

These results suggest that CML patients with increased weight at baseline should be followed and carefully monitored if treated with standard dose imatinib frontline for a possible early switch to a second generation TKI or, as an alternative, should preferably be candidate to receive these drugs as a first line therapy.