Analysis of the Short-Term Efficacy of Decitabine Combined with Low-Dose Cytarabine in the Treatment of JMML

Objective: Juvenile myelomonocytic leukemia (JMML) has both the disease characteristics of myelodysplastic syndrome and myeloproliferative neoplasm. Currently, hematopoietic stem cell transplantation (HSCT) is the only possible cure. Most of the newly diagnosed pediatric patients with JMML have high tumor burden, rapid disease progression, and may not tolerate HSCT. This study explored the short-term efficacy of decitabine combined with low-dose chemotherapy in the treatment of JMML before transplantation.

Methods: A retrospective analysis of the patient files of 9 cases of JMML was performed from January 2019 to May 2020. All patients were given decitabine 20mg/m²× 5 days, supplemented with a small dose of cytarabine (50-100mg/m²×3~5 days), and/or etoposide (50mg/m²×3~5 days) chemotherapy. Each treatment interval is 3~4 weeks, bridging with HSCT after 3~4 treatment courses.

Results: The median age of onset of 9 cases of JMML was 2 years old (0.5~4 y), male to female ratio was 8:1, the median size of spleen was 6.4cm (2.9~9.8cm) under the costal arch, and WBC was 28.03×10⁹/L (7.3~127.69×10⁹/L), monocytes were 9.25×10⁹/L (1.66~15.79×10⁹/L) at diagnosis. There were 8 cases in the high-risk group and 1 case in the low-risk group. Second-generation sequencing results show that 7 cases carried PTPN11 somatic mutations. Five in 9 cases had two kinds of classic JMML mutations, and 1 case had only NRAS mutation. Seven patients had normal chromosomal karyotypes, and 3 patients had abnormal 8, 11, and 18 chromosomes, respectively. Median treatment courses with decitabine are 3 courses (1~5 courses), the response rate of one course is 77.8% (7/9), the response rate of three courses is 80% (4/5), one case from high-risk group achieved complete remission after treated with 4 courses of decitabine and low-dose chemotherapy. The five-month progression-free survival rate was 77.8% (7/9).

Conclusion: Treating JMML with decitabine combined with low-dose chemotherapy, can reduce patients' tumor burden, improve the general condition, and obtain approximately 80% clinical response rate. Decitabine combined with low-dose chemotherapy can be used as a treatment option for JMML before HSCT.