Objective: To investigate the incidence and clinical features to probe the risk factors of hemorrhagic cystitis (HC) in children and adolescents with hematological diseases post haplo-hematopoietic stem cell transplantation (haplo-HSCT) . Methods: Medical records of 62 children and 27 adolescents with hematological diseases treated with haplo-HSCT between 2015 and 2016 were analyzed. Results: Of 89 cases (56 boys and 33 girls) , 44 patients were diagnosed with ALL, 33 AML, 3 AHL and 9 MDS. HC occurred in 32 of the 89 patients with an incidence of 36%, including 6 with grade Ⅰ, 16 with grade Ⅱ, 8 with grade Ⅲ, 2 with grade Ⅳ HC, respectively. The median time of HC onset was 25 days (range 2-55 days) after haplo-HSCT with the median duration as 19 days (range 3-95 days) , all of them were cured. The incidence of HC was lower in the group of children than that in the group of adolescents (27.4% vs 55.6%, χ²=6.466, P<0.05) , and the incidence of HC was higher in the group of patients who were ≥5 years old than that in the group of patients who were <5 years old (0 vs 34%, χ²=4.043, P<0.05) . Conclusion HC is one of common complications in children and adolescents with hematological diseases post haplo-HSCT, older age was associated with increased mortality.

Objective To compare the dosimetric differences of volumetric modulated arc therapy (VMAT) with flattening filter(FF) and flattening filter-free(FFF) modes in hippocampal avoidance whole brain radiotherapy. Methods We included 15 patients with hippocampal-sparing whole brain radiotherapy, and designed two radiotherapy plans of FF-VMAT and FFF-VMAT for each patient. On the premise of meeting clinical dose requirements, the two plans’ dosimetry, total number of monitor units, and beam-on time were compared. Results There were no significant differences in the target coverage, conformity index, and dose gradient of the FF-VMAT and FFF-VMAT plans (P > 0.05). The D_max, D_100%, and D_mean to the hippocampal tissue were significantly lower with FFF-VMAT [(15.13 ± 0.38) Gy, (7.12 ± 0.34) Gy, and (9.76 ± 0.43) Gy, respectively)] than with FF-VMAT (16.46 ± 0.56) Gy, (7.72 ± 0.28) Gy, and (10.54 ± 0.48) Gy, respectively)] (P < 0.05). The D_max to the left and right lenses and the D_mean to the left and right eyeballs with FFF-VMAT were (7.26 ± 0.43) Gy, (6.29 ± 1.13) Gy, (11.01 ± 0.94) Gy, and (9.78 ± 1.13) Gy, respectively, which were significantly lower than FF-VMAT’s corresponding doses of (8.09 ± 0.66) Gy, (7.80 ± 0.74) Gy, (11.38 ± 1.09) Gy, and (11.05 ± 0.90) Gy, respectively (P < 0.05). The doses to other organs at risk including the optic nerve and optic chiasm were all controlled within the safe dosage ranges, with no significant differences between the two plans (P > 0.05). The FFF-VMAT plan had a significantly greater number of monitor units and a significantly shorter beam-on time than the FF-VMAT plan (P < 0.05). Conclusion Both FF-VMAT and FFF-VMAT can meet the clinical requirements, with FFF-VMAT having better hippocampus and lens protection, shorter beam-on time, and higher treatment efficiency.