[Clinical Characteristics of Patients with Ph⁺ Mixed Phenotype Acute Leukemia]

To investigate the clinical biological characteristics and prognosis of the patients with mixed phenotype acute leukemia with t(9;22)(q34;q11.2) and/or BCRABL1 (Ph⁺ MPAL).

The morphological, immunological, cytogenetic, and molecular features of 33 in patients with Ph⁺ MPAL were retrospectively analyzed in our center from June 2002 to June 2016 according to the scoring proposal of European Group for the Classification of Acute Leukemia(EGIL )1998 and WHO 2008 criteria. All the cases were either treated with acute lymphoblastic leukemia (ALL) induction regimen or combined chemotherapy regimens for both acute lymphoblastic and acute myeloid leukemia,part of which also received tyrosine kinase inhibitor(TKI) and 5 cases underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT) after complete remission.

Ph⁺ MPAL occurred predominantly in male patients (ratio of M/F was 1.75∶1), and a high WBC counts at diagnosis; the WBC count was higher than 30×10⁹/L in 25 patients( 75.8% )， and appeared higher than 100 ×10⁹/L in 13 patients ( 39.4%). Among all the 33 Ph⁺MPAL patients, 32 (97.0%) had a myeloid / B-lymphoid (M/B) phenotype， and 1 case(3.0%) had a myeloid/ B-lymphoid/ T-lymphoid/ (M/B/T) phenotype. There was no patients displayed myeloid / T-lymphoid (M/T) or B-lymphoid/ T-lymphoid/ (B/T) phenotype. 19 of all cases(57.6%) met the diagnosis criteria of Ph⁺MPAL based on EGIL 1998 criteria, while the remaining 14 cases can be diagnosed as Ph⁺ MPAL by WHO 2008 classification,but excluded as Ph⁺MAPL by EGIL 1998.Karyotype analysis was successfully performed in 31 cases, and out of them 13 (41.9%) had a sole Ph chromosome, 10 (32.3%) had additional chromosome aberration and Ph chromosome was not found in 8 cases (25.8%) .In 31 patients the fusion gene BCR/ABL (P190、P210) was detected,including 17 (54.8%) cases with the p190 BCR/ABL transcript, 8 (25.8%) cases with the p210 BCR/ABL transcript, 4 (12.9%) expressing both transcripts and 2 (6.5%) without any one of these 2 transcripts. 24 out of 33 patients (77.4%) achieved complete remission after induction therapy. The median time achieving CR was 43(26-98)days. The CR rate of patients treated with and without imatinib after the first inducion treatment was 81.3% and 46.7%,respectively (P⁺0.05). Within the 17 patients treated with imatinib at induction stage，2 of which became BCR/ABLnegative．At consolidation chemotherapy stage, 9 out of 16 patients became BCR/ABL negative, including 3 patients already subjected to HSCT. The median time reached to BCR/ABL negative was 2.87（1.13-9.20）months.

Ph⁺ MPAL is more common in male, and inclined to high WBC counts at diagnosis. Myeloid/B lymphoid phenotype is more common, and the prognosis of patients with Ph⁺MPAL is poor. Imatinib and allogeneic hematopoietic stem cell transplantation may improve survival of patients with Ph⁺MPAL.