Analyzing The Dose-volume Parameters Of The Lung In Lymphoma Patients After Mediastinal Radiotherapy

Purpose:To analyze the relationship of radiation induced lung injury and the dose of irradiated lung in Hodgkin's lymphoma patients who have received mediastinal irradiation;and to estimate the differences of the dose and volume of the irradiated lung among the three different radiation treatment plannings(2D mantle field,3DCRT and sIMRT) in lymphoma patients.Materials and Methods:Among 50 lymphoma patients who had receivedmediastinal irradiation between July,2006 and May,2008 in Fudan University Cancer Hospital,20 patients with complete follow-up were investigated.All the patients had CT simulation,and the clinical target volumes(CTV) and the normal tissues were outlined following the principle of involved field.These patients were divided into two groups,one with radiation-induced lung injury(fibrosis group) and the other without radiation-induced lung injury(non-fibrosis group).We delineated the lung fibrosis and analyzed the dose of normal lung tissue and fibrosis.Ten patients were randomly chosen from all the 50 patients,all their target volumes and normal tissues were outlined.Three different treatment plannings(two dimensional mantle field,2D RT;three dimensional conformal radiotherapy,3DCRT;simplified intensity modulated radiotherapy,sIMRT) were worked out for each patient.We analyzed the differences of the dose and volume of the irradiated lung.Results:Among the 20 patients with sufficient follow-up,radiation induced lung fibrosis was found in 12 patients.The difference in V15,V20,V25,V30,MLD were significant between the fibrosis group and non fibrosis group(P＜0.05). V5,V10,V40 are also higher in the fibrosis group but not significant(P＞0.05).The mean dose of the fibrosis regions of all patients in the fibrosis group is 3800.56±260.79 cGy.Comparing the 2D RT and 3DCRT,the V5,V10,V15,V20, V25,V30,V35 and MLD were reduced with 3DCRT(P＜0.05).V40 was increased (P＞0.05);the V5,V10,V15,V20,V25,V30,V35 and MLD were also lowered with sIMRT(P＜0.05),and V40 became higher with sIMRT when comparing with 2D RT (P=0.02).The V5 was increased whereas V10,V15,V40 and MLD were reduced (P＞0.05) with sIMRT comparing with 3D CRT,and the V20,V25,V30,V35 were lowered down with sIMRT.(P＜0.05).There was a reduction in V5,V10,V15,V20, V25,V30 and the mean dose(P＜0.05),and a rise in V35(P＜0.05) while V40 is the same with 3DCRT compared with the 2D RT.There was also a reduction in V5,V10, V15,V20,V25,V30 and the mean dose(P＜0.05),and a rise in V35 and V40(P＞0.05) with sIMRT compared with the 2D RT.compared with 3DCRT,there was a reduction in V10,V15,V20,V25,V30,V35 and the mean dose(P＜0.05) while V5 was reduced and V40 was increased(P＞0.05)Conclusions:Radiation induced lung injury would occur with a relatively higher V15,V20,V25,V30 and MLD.Radiation induced lung fibrosis took place in region with high radiation dose of the lung.Compared with 2D mantle field irradiation, either 3DCRT or sIMRT can reduce the radiation dose and protect the normal lung tissue.Compared with 3DCRT,sIMRT can reduce the volume of high-dose region without an increase of the volume of the low-dose region within the lung.sIMRT can not reduce the MLD statistically.3DCRT and sIMRT can also reduce the dose delivered to the heart compared with 2D mantle field irradiation.Compared with 3DCRT,sIMRT can reduce the volume of the high dose region and the mean dose of the heart.