Abstract: Objective:To reduce the hematologic toxicity and adverse reactions of ruxolitinib on myelofibrosis（MF）patients,a pilot study of low dose ruxolitinib combined with TCP therapy was conducted and the results were presented as follows.Method:A total of 19 patients with MF,who were treated in the Department of Hematology,Shanghai No.6 People's Hospital,were given low dose of ruxolitinib combined with TCP（ruxolitinib 5 mg,Bid;thalidomide 50 mg QN;calcitriol 25 mg,Bid;prednisone 10 mg QD）from February 1,2019 to March 31,2020.Ordinary blood test and hepatic and renal functions were tested monthly,liver and spleen ultrasound and myeloproliferative neoplasm symptom assessment form total symptom score（MPN-SAF-TSS）were checked every three months during the study.Result:Among 19 patients,10 cases were male and 9 cases were female;the median age was 63（31-82）,7 cases（36.84%）were＜60 years old,7 cases（36.84%）were 60-74 years old and 5 cases（26.32%）were ≥75 years old.There was 1 case with hyperleukocytosis（WBC≥25×10⁹/L）,5 cases with anemia（Hb＜100 g/L）,and 3 cases with thrombocytopenia（PLT＜100×10⁹/L）.Thirteen patients（68.42%）were with PMF,3 patients（15.79%）with post-ET MF and 3 patients（15.79%）with post-PV MF.DIPSS prognostic grading group:9 cases（47.37%）in the intermediate-risk-1 group and 10 cases（52.63%）in the intermediate-risk-2 group.MIPSS70 score:13 cases（68.42%）in the middle-risk group and 6 cases（31.58%）in the high-risk group.Karyotype:1 case（5.26%）with very-high-risk karyotype,16 cases（84.21%）with favorable karyotype and 2 cases（10.53%）with unfavorable karyotype.Second-generation sequencing:14 cases（73.68%）were positive for JAK2 V617 F mutation,2 cases（10.53%）were positive for CARL mutation,3 cases（15.79%）were triple negative for JAK2,CALR and MPL,5 cases（26.32%）had one high risk mutation,1 case（5.26%）had two high-risk mutations.Before treatment,the MPN-SAF-TSS score was 33（11-60）points and 15 patients（78.95%）were confirmed to have splenomegaly by ultrasound.The median treatment time was 6（3-13）months.There was 1 case of alleviated hyperleukocytosis,anemia and thrombocytopenia after treatment,respectively.After treatment of 19 patients,the lowest MPN-SAF-TSS score was 17（8-35）points,and the score decreased by 13（3-45）points,4 patients（21.05%）had a score reduction of ≥50%（maximum 75%）.Thirteen cases（86.67%）out of 15 patients with splenomegaly achieved different degrees of spleen response,with a shrinkage ratio of 38.67%（4.36%-53.26%）,and 8 cases（53.33%）achieved a ≥35% reduction from baseline in spleen size.The 19 patients receiving this treatment had not withdrawn at present.One case showed a decrease in hemoglobin and platelet counts during the first month of treatment（returned to normal after 2 months of treatment）,and another case showed severer anemia during the second month of treatment（rebounded after 3 months of treatment）,and the remaining 17 patients had no hematological adverse events.No grade Ⅲ/Ⅳ non-hematological adverse event was observed.Grade Ⅰ/Ⅱ non-hematological adverse events,including 1 case of constipation and 2 cases of abdominal distension,were improved after gastrointestinal treatment.No patients discontinued or adjusted the dosage of therapies due to adverse events.Conclusion:Low dose ruxolitinib combined with TCP therapy appears to be a safe and effective treatment for MF patients.It reduces incidence of anemia and thrombocytopenia compared with conventional doses of ruxotinib and offers a treatment option for elderly MF patients,even for those super elderly patients over 75 years old.For cases of insensitivity to spleen reduction,the dose of ruxotinib needs to be adjusted.