Clinical And Dosimetric Research Of Radiotherapy In Brain Metastatic Tumors

Objective: To explore the clinical significance of intensity-modulated radiotherapy of the brain metastases.Methods: In the period between June 2009 and July 2010,A total of 18 patients were treated by 5-field intensity modulated radiotherapy. There were 11 male and famale patiens ,with a mean age of 62yr (range47-73 yr),The primary tumor were diagonosed by histologic or cytological with 14 lung cancer and 1 submandibular gland cancer and 1 esophagus cancer and 2 breast cancer , Before the treament all the patients have neurologic symptom like headache ,nauseating, vomiting or movement disorders, All the brain metastasis tumors were diagnosed by brain MRI, There were 0 case for GPAⅠand GPAⅡ, 11 cases for GPAⅢ,7 cases for GPAⅣaccording to GPA grade. There are 12 patients with stageⅢand 6 patients with stageⅣaccording to RPA grade. The prescription dose was 40-56Gy (PTV-G: brain metastasis tumors) , 2.2-3.0Gy per fraction; 36-42Gy (PTV-C: whole brain) in 20 fractions, 1.9-2.4Gy per fraction. Simultaneously integrated boosting, The 95% equi-dosage line included the target area. Response rate was evaluated by brain MRI after radiotherapy according to response evaluation criteria in solid tumors: Revised RECIST guidline.(version 1.1) , We evaluate the acute side effect according to Radiation therapy oncology group (RTOG) acute radiation injury standard. The Kaplan-Meier methods were used for calculation of the survival rate; The effective rate =(CR+PR)/all the patients in group ,Results: The mean follow up period was 6 months(4-13months), the follow up rate is 94.4%, survival rate of one year was 71.2%. The complete response (CR) rate was 22.2%(4/18), partial response(PR) was 66.7%(12/18), stable disease(SD) was 5.6%(1/18) and progressive disease(PD) was 5.6%(1/18) respectively, The effective rate was 88.9%(16/18). The main toxicities were bone marrow depression, nausea, vomiting and brain edema ,but all toxicities were grade 1 or 2. The syndrome can be alleviated after treatment. All the patients can tolerate the radiation toxicities. There are not apparent radiation-induced brain injure.Conclusion: IMRT can bring about high local control rate and low toxicities , so it is feasible and highly effective Objective: To evaluate the characteristics of three-dimensional conformal radiotherapy and intensity modulated radiation therapy plans of the brain metastasis and to find out the better technique to achieve improved dose homogeneity and sparing of normal tissues for the brain metastasis tumors.Methods: We selected 10 brain metastasis tumor patients to compare the treatment plan, who hospitalized in the radiation Department of our Hospital and were accepted IMRT. We designed(2fields for the whole brain+ 3fields as a boost treatment for the GTV ) three-dimensional conformal radiotherapy(3DCRT) and 5fields intensity modulated radiation therapy(IMRT)treatment plans for each patient by treatment planning system(TPS), and evaluated the target isodose distribution of target and normal tissue like CI, IC,Dmean,Dmax according to dose-volume histogramResults: Between the three-dimensional conformal radiotherapy and IMRT plans, statistically significant differences were found in CI(t=6.082 p=0.000 ) and IC(t=-6.534 p=0.000 ) of PTV-G, there were statistically significant differences were found in CI(t=5.57 p=0.000 )and IC(t=-4.227 p=0.002 ) of PTV-C,with the higher for IMRT and lower for 3DCRT. There was no statistically significant difference in Dmean of the organs like lens-L(t=0.330 p=0.753 ) and Lens-R(t=2.379 p=0.055 ) and eyeball-L(t=-0.668 p=0.529 ) and eyeball-R(t=2.111 p=0.079 )。There was also no statistically significant difference in Dmax of the organs like brain stem(t=2.447 p=0.05 ),optic nerve-L (t=-1.047 p=0.336 )and optic nerve-R (t=-1.848 p=0.114 )and optic chiasm. (t=2.409 p=0.053 )Conclusion: There is statistically significant differences in CI and IC(p<0.05), with the higher for IMRT and lower for 3DCRT. But the advantage that the normal organ can be preserved better in the IMRT is not found obviously.