Acute Haematological Toxicity And Dosimetric For Patients Treated With Craniospinal Irradiation:Helical Tomotherapy Versus Conventional Radiotherapy

Objective①To compare the acute haematological toxicity for patients treated with craniospinal irradiation (CSI) using helical tomotherapy (HT) and conventional radiotherapy (CRT).②To compare the dosimetric for patients treated with CSI using HT,3DCRT and CRT.Methods①We retrospectively analyzed the acute haematology data of70hospitalized patients treated with CSI from Jan2000to Mar2013. Patients were divided into helical tomotherapy group (CSI-HT,14cases) and conventional radiotherapy group (CSI-CRT,56cases). Myelosuppression of two groups were recorded and compared according to CTCAE v3.0. Difference was compared by X2test.②10patients treated with CSI were enrolled. The scanning CT images were transmitted to Treatment Planning System (TPS), where painting the volumes of PTV and organ at risks (OARs). CRT plan,3DCRT plan and HT plan were designed for each patient simultaneously with the same prescription dose(PTV DT36Gy/18f). Then the dose distributions of PTV and organ at risks were analyzed with TPS. Difference was compared by t test. Results①The incidence of leucopenia, thrombocytopenia and decreased hemoglobin were100%,100%,78.6%in CSI-HT group and91.1%,67.9%,32.1%in CSI-CRT group, respectively (P<0.05); Moreover, the incidence at grade Ⅲ～Ⅳ were85.7%,50%,14.2%in CSI-HT group and35.8%,10.7%,0in CSI-CRT group, respectively (P<0.05). There were10.7%(6/56) patients in CSI-CRT group and 92.8%(10/14) patients in CSI-HT group were delayed radiotherapy due to myelosuppression (P<0.05). The average myelosuppression time was11.5d in CSI-HT group and17.37d in CSI-CRT group (P<0.05). Myelosuppression was more serious in patients treated with induction chemotherapy than those without induction chemotherapy before radiotherapy.(2) HI,CI and DVH in HT group is superior to CRT and3DCRT group. The HI and CI in CRT group,3DCRT group, HT group are1.16±0.05and1.02±0.01、1.2±0.04and1.01±0.01、1.03±0.01and1.01, respectively (P<0.05). The Dmean, Dmax and V20of OAR is CRT>3DCRT> HT;The V5of OAR is HT>3DCRT>CRT; difference in V10is not significant.Gonclusion①CSI-HT shows more serious hematologic toxicity compared with CSI-CRT, which may relate to low dose exposure range for bone marrow and whole body, chemotherapy, etc. More attention and researches should be applied to the acute haematological toxicity of CSI-HT.②HT resulted in more homogeneous PTV dose distribution and better sparing of OAR. However, the long-term effects of tomotherapy dose avoidance on large volume low dose radiation are not yet known.