Prognostic value of the individual rate of BCR-ABL decline for major molecular response achievement for chronic myelogenous leukemia patients

Relevance. CML patients remain heterogeneous group. Several studies in recent years were aimed to personalize treatment based on individual patients' characteristics. Aim of study. The aim of our study was to assess prognostic value of individual BCR-ABL decline rate in the first three months of CML therapy to predict optimal response. Patients and methods. Fifty-four patients with chronic phase CML were included in the study. Forty-one patients started treatment with Imatinib 400 mg/day, 12 patients started with Nilotinib 600 mg/day and 1 patient started with Dasatinib 100 mg/day. BCR-ABL level was determined by International Scale at diagnosis, 3, 6 and 12 months of ITK therapy. The ratio of BCR-ABL levels at 3 months to baseline for each patient, frequency of achieve early molecular response at 3 months (10% by IS) and MMR at 12 months were assessed; in addition, we calculated ratio of BCR-ABL levels at 3 months to BCR-ABL levels at 1 month. Results. Twenty-six out of 34 patients (76,5%) with ratio of BCR-ABL levels at 3 months to baseline below than 0,1 achieved MMR at 12 months, while only 9 of 20 patients (45%) with ratio more than 0,1 had optimal response (p=0,02). Ratio of BCR-ABL levels at 3 months to 1 month showed much better results with the same (0,1) cut-off value - 5 out of 6 patients (83,3%) with ratio BCR-ABL at 3 months to 1 month below than 0,1, while only 1 patient (16,7%) with ratio more than 0,1 achieved optimal response (p=0,04), respectively. Application of early molecular response at 3 months (10% by IS) yielded worse discrimination results: 33 of 46 (71,7%) patients with BCR-ABL level ≤10% at 3 months, whereas 2 of 8 (25%) patients with BCR-ABL >10% had MMR at 1 year (p=0,02), respectively. Furthermore, application of our ratio cut-off value among patients with BCR-ABL level ≤10% at 3 months allowed us to revealed additional 5 high-risk patients have not reached MMR at 1 year of therapy. Conclusion. Our study showed that individual rates of BCR-ABL decline from baseline to 3 months and to 1 month might be useful as an optimized predictors of outcome for CML patients (MMR at 1 year of treatment).