RESUMO
Objective To investigate the impact of four different collimator angle optimization techniques on the planning target volume (PTV) and organ at risk (OAR) during intensity-modulated radiotherapy (IMRT) for gastric cancer.Methods Ten patients with gastric cancer undergoing IMRT in Zhongnan Hospital of Wuhan University from 2015 to 2016 years were recruited in this study.All IMRT plans were designed by conventional five fields (330°,10°,45°,90°and 180°).In the Eclipse treatment planning system,four different collimator angle optimization techniques with consistent planning optimization parameters were employed to design the IMRT plan.Collimator angle optimization techniques included the following aspects.The collimator angle was set at 0 degree (CL0),collimator angle was set at 90 degree (CL90),Eclipse automatic collimator angle optimization (CLA) was adopted and collimator angle was set as the angle when the distance between X-Jaws and PTV (CLx) was the shortest.The dosimetric parameters mainly included the conformal index (CI) of PTV,the homogeneity index (HI),the mean dose (Mean),and the dosage of OAR.The treatment time (Time),monitor unit (MU),control point (CP),split field (SF) and conformal distance (Fx) were also considered.Results Regarding CL0 as the control,the CI,HI and Mean did not significantly differ among four collimator angle optimization techniques (all P＞0.05),whereas CLx could significantly increase the average dose of PTV in the target area (P＜0.05);CLx optimization reduced the liver (V30 reduction by 1.54％),left kidney (V12 decrease by 1.46％),right kidney and other OARs,whereas it slightly increased the maximum dose of the small intestine and spinal cord (＜1％).CLgo and CLA optimization elevated the dose of OAR in gastric cancer.Among four different collimator angle optimization techniques,CLx optimization reduced the MU (25.02％),CP (26.03％),Fx (20.27％) and SF (by 1.3separate fields on average) and treatment time (10.03％).CLgo and CLA optimization could decrease the MU,CP,Fx and SF.CL90 optimization had certain advantages in shortening the treatment time,whereas CLA optimization could prolong the treatment time by 5.04％.Conclusions During IMRT for gastric cancer,CL90,CLA and CLx collimator angle optimization techniques can obtain comparable dosimetry distribution to CL0 optimization technique,which can reduce the MU,decrease the radiation leakage,shorten the treatment time and improve treatment efficiency.
RESUMO
Objective To compare the efficacy and resistance between S?1 combined with radiotherapy and S?1 alone in the treatment of elderly patients with locally advanced gastric cancer. Methods Fifty?eight elderly patients with unresectable locally advanced ( stage Ⅲ) gastric cancer were randomly and equally divided into S?1 combined with concurrent radiotherapy group ( experimental group ) and S?1 alone group ( control group ) . The experimental group received 4 cycles of S?1 treatment with each cycle containing two?week oral administration of S?1 at a dose of 40 mg/m2 twice a day followed by one?week drug withdrawal. Gastric intensity?modulated radiotherapy was performed concurrently with a dose of 45 Gy ( 1. 8 Gy per fraction) . The control group received the same dose of S?1 alone. Short?term outcomes and adverse reactions were evaluated in the two groups. Comparison was made by chi?square test. Results All patients completed the planning treatment. The experimental group had significantly higher objective response, disease control, and symptom remission rates than the control group ( 52% vs. 24%, P=0. 03;76% vs. 45%, P=0. 016;86% vs. 48%, P=0. 005) . There were no significant differences in the incidence of nausea and vomiting, anorexia, leukopenia, diarrhea, or thrombocytopenia between the two groups ( all P>0. 05) . Conclusions S?1 treatment combined with concurrent radiotherapy improves the short?term outcomes and causes tolerable toxicities in the treatment of elderly patients with locally advanced gastric cancer.
