Determination Of Internal Target Volume For Esophageal Carcinoma

Objective: Esophageal carcinoma is the most common cancer in China. Radiotherapy has always been the main treatment methods because most of patients suffered from the locally advanced stage of this disease.However,the 5-year local control rate was only 10% for patients treated at routine radiotherapy. Recent technologic advances in radiotherapy, such as the routine clinical use of three-dimensional conformal radiotherapy (3D-CRT) ,have made high-dose radiation feasible in routine clinical practice. 3D-CRT is a mode of precision radiation therapy which offers the prospect of improved locally control rate and survival rate.But the potential dosimetric superiority of 3D-CRT offers the advantage of better tumor target coverage and critical normal tissue sparing.In 3D-CRT for esophageal carcinoma, the tumour position will change with the breath motion. This change is one important gist for confirming the scope of the internal target volume (ITV). How to confirm and control the scope of the affection moving with the breath motion, and nicely sketch the treatment target volume,not leave out the affection section when reducing the radiation to well organic around, have become to an important problem in current research. Recently, the several different methods that the scholar have bring forward which resolve the problem for confirming the ITV because of the breath motion are not very well.This study depend on three dimensional conformal treatment planning system (TPS) and image fusion, To observe the respiratory effects on 3D-CRT of the esophageal carcinoma targets in order to obtain optimal values for ITV.Method: From December 2007 and December 2008,13 patients with Stage II to IIIa of esophageal carcinoma were obtained at the General Hospital of Armed Police Forces. 9 were squamous cell carcinoma (SCC) and 4 were adenocarcinoma (ADC) . 6 patients with middle esophageal carcinoma and 7 patients with lower esophageal carcinoma.All of the patients were performed the CT scanning in three levels: one acquisition in free breathing (FB), one at end expiration (EBH), and one at end inspiration (IBH).The scope of scanning must include all esophagus.The interval between two scanning is one minute at least in order to help the patient to resume the quiet breath rhythm. Results of all scans were transferred to the treatment planning system(TPS)and fused each other.Then outlined the gross tumor volume(GTV) and named the target in free breathing (GTVFB), and named the target at end expiration (GTVEBH), and named the target at end inspiration (GTVIBH).The motion of tumor and disphragmatic muscle were measured between two point which was markd by the target center of GTV for each respiratory level. statistical analysis using SPSS13.0 software.Result:The target center of GTV had some deviations along X,Y,Z axis. The deviation In 6 patients with middle esophageal carcinoma were (0.50±0.42)cm;(0.23±0.26)cm;(0.35±0.40)cm;The deviation In 7 patients with lower esophageal carcinoma were(1.73±0.94)cm;(0.40±0.33)cm;(0.89±0.53)cm.In all 13 patients,to take GTVFB as the isocenter, the deviation of target between GTVIFB and GTVEFB were (0.50±0.34)cm at superior(;1.17±0.72)cm at inferior(;0.56±0.33)cm at left lateral;(0.35±0.23)cm at right lateral;(0.57±0.39)cm at anterior;(0.40±0.31)cm at posterior.The ITV margin for 3D conformal radiotherapy was 0.86cm at superior,1.92cm at inferior,0.72cm at left lateral,0.47cm at right lateral,0.77cm at anterior,0.55cm at posterior when 95% of GTV motions were taken into measured.Conclusion: The GTV geometrical center of esophageal carcinoma had some deviations along X,Y,Z axis. It is show that the breathing motion of tumor had statistical significance in madeing ITV. This numerus of ITV margin is so justified that use of esophageal carcinoma be recommended in clinic.This study succeed to collecting the scan image which in the end of the inspiration and the exhalation when the patient locating on the quietly breathing state, and measured the motion by image fusion technique in the radiotherapy plan system, This method is so precise to obtain the numerus of ITV margin,then recommend to confirm the individualized ITV for every patient use this method.