Study Of Craniospinal Irradiation With Tomotherapy In Patients With Medulloblastoma

Objective To compare the dosimetric difference of craniospinal irradiation in patients withmedulloblastomabetween Three dimensional conformal radiotherapy(3D?CRT)?volumetric modulated arc therapy(VMAT)and Tomo Therapy(TOMO),analyse the setup errors and acute toxicity in radiotherapy,give a best choice to patient with medulloblastoma.Methods Between October 2012 and September 2016,the records of 20 patients with medulloblastoma received craniospinal irradiation(CSI)with tomotherapy(TOMO)10 patients?s CT images were transferd to 3D?CRT?VMAT and TOMO planning stations respectively.After that we compared the conformity index(CI),homogeneity index(HI)and dose of organ at risk(OAR);All patients received MVCT scaning before radiation was delivered,The MVCT images were registered with the kilovoltage CT(k VCT)images,the setup errors of left?right(X)? anterior?posterior(Y)?superior?inferior(Z)and transverse profile rotation(Roll)were obtained by matching MVCT with k VCT;A study of acute toxicity during CSI was conducted according to CTCAE v4.0.In acute toxicity,patients were divided into normal/mild suppression group(0/I/II)and severe suppression group(III/IV)according to the decline in the degree.The correlation of gender?age?induction chemotherapy,radiation dose of spinal cord and acute toxicity was examined.Results Dosimetry The HI of 3D?CRT?VMAT and TOMO was 1.16±0.04?1.12±0.04?1.05±0.002,respectively.The CIwas 0.62±0.08?0.76±0.07?0.81±0.04,respectively.TOMO has obviously advantagein terms of HI and CI(P<0.05).In organ at risk,TOMO and VMAT has obviously advantage in terms of Dmean and V10 of heart and Dmax of lens?optic nerve?stomach and bowel(P<0.05).3D?CRT has obviously advantage in terms of Dmean and V5 of lung and Dmean and V10 of kidney(P<0.05),TOMO has the lowest Dmean and V10 of liver(P<0.05).Setup errors Three hundred and sixteen MVCT images of the part of head?neck,the setup error in X,Y?Z and Roll axis were(?0.72±2.95)mm?(?0.54±3.43)mm?(0.19±2.95)mm and(?0.18±2.93)°;One hundred and twenty five MVCT images of the part of chest?abdomen,the setup error in X,Y?Z and Roll axis were(?1.35±7.34)mm?(?0.14±0.97)mm?(0.06±4.40)mm and(0.51±1.13)°Acutetoxicity The incidence of fatigue?vomiting and headache was 55%(11/20)?45%(9/20)and 25%(5/20),respectively;the incidence of leucopenia was 95%(19/20)while that of thrombocytopenia was55%(11/20)and 45%(9/20)for hemoglobin.Severe suppression of themwere 35%?20% and 0.Leucopenia appeared with in 2 weeks from the beginning of radiotherapy.Chemotherapy was correlated with haematological toxicity(P<0.05)and was not correlated with gender,age,induction chemotherapy and radiation dose of spinal cord(P>0.05).Conclusion TOMO has obviously advantage compared to 3D?CRT?VMAT in terms of homogeneity index(HI)and coverage index(CI)and the protection of organ at risk,and it has low incidence of severe acute toxicity;The MVCT image guide of Tomo Therapy can correct the setup errors of craniospinal irradiation and improve the accuracy of radiotherapy.Therefore we suggested TOMO might be a good clinical choice for CSI treatment.