Analysis Of Changes In Pulmonary Function In Patients With Lung Cancer Between Pre-intensity Modulated Conformal Radiotherapy And Post-intensity Modulated Conformal Radiotherapy

Objective:To investigate the impact of intensity modulated conformal radiotherapy(IMRT)on pulmonary function in patients with lung cancer,try to find a sensitive indicator of radiation-induced lung injury. We conducted a controlled study of pulmonary function changes between pre- and post-IMRT on patients with mid and advanced lung cancer or that can not tolerate surgery.Methods:Excluding serious kidney and heart disease,69 patients with lung cancer were selected in study from January 2014 to June 2014. Based on the presence of obstructive ventilatory dysfunction before radiotherapy,patients were divided into two groups,ventilatory dysfunction group(40 cases)and normal ventilatory function group(29 cases). First,patients in both group took intravenous enhanced CT scaning to get imitative position and sketch gross target volume of tumer(GTV) and endanger organs. Second, expanded GTV equably for 6~8mm to get clinical target volume(CTV). In the end, expanded CTV flatly for 5mm and vertically for 10 mm to get planning target volume(PTV). Simultaneously integrated boosting(SIB) prescribed dose:PTV 60Gy/30times;Conventional fractionation irradiation: 2.0 Gy per time,five times per week,meet the standards for bilateral pulmonary V10≤40%,V20≤30%,V30≤18%(V10,V20,V30 stands for the percentage that the volume of irradiation with 10 Gy,20Gy and 30 Gy accounts for the whole lung). Determined resting pulmonary function test pre-IMRT and post-IMRT within one week respectively,including pulmonary ventilation function, diffusion function and airway resistance. According to patients’ gender,age,height,weight and measurement of hemoglobin calculated the expected value automatically. According to European respiratory society(ERS)of Lung function and pulmonary function testing standards guide,the procedure of pulmonary function testing as follows: For diffusion function testing,patients should take a upright sitting position, inhale quickly within 2~4s then take a breath holding for about 10 s without air leadage or Muller and Valsalva motions,then exhale smoothly without hesitation and interrupt within 2 ~ 4s. For impulse osillometry airway resistance measurement,patients should take a upright sitting position,maintain head the natural level or slightly pitching and bite the mouthpiece tightly preventing air leakage and breath unobstructed;At the status of functional residual volume position let patients breath in normal frequency,without breathholding,leakage and swollowing,to make a smooth driftless curve. Tidal volume respectively male>450ml/min,female>350 ml/min. Start recording for about 40 seconds when breathing steady. Pay attention to the trend of impedence changes with tidal breathing(Z-time)as quality control. Repeated for 3 times then elected the best one. Pulmonary function examination executed in 8:30am~10:30am before which must conduct environmental calibration including room temperature,room pressure,humidity,ambient atmosphere and body temperature pressure saturated(BTPS). At room temperature for 18 ~24℃,relative humidity of 50% to 70%. Instrument’s volume calibration had to use 3.0L calibration tube for high, medium and low flow. Standard test gas composed of 21.3% oxygen, 0.3% carbon monoxide,0.3% methane,0.3% acetylene. And filling the rest with nitrogen for balance.Results:According to the radiation therapy oncology group(RTOG)and European organization for research and treatment of cancer(EORTC)’s criteria, general acute radiation-induced lung injury occurrence as follow:Level 0 73.7%,1 level 1 of radioactive pneumonia by 15.8%;level 2 of radiation pneumonia by 7.9%,level 3 of radioactive pneumonia by 2.6%. 10.5% incidence of acute radiation pneumonia in level 2 and above. Resting state of pulmonary function changes before and after radiotherapy:In ventilation dysfunction group,in the end of IMRT for 1 month within 1 week. After radiotherapy,DLCOc-SB which can reflect Lung diffusion function was significantly reduced(P=0.049,P<0.05). In the same time,DLCOc/VA was also significantly reduced(P=0.000,P< 0.01). And air resistance indicators such as Zrs(Respiratory Impedance),Rc(Central airway resistance),Rp(peripheral airway resistance),Fres(Resonant frequency),R5(Resistance at 5 Hz),R20(Resistance at 20 Hz),X5(Reactance at 5 Hz)all reduced more or less,but only the Rc and the R20 reducing were statistically significant(P=0.038,P=0.008,respectively). Lung ventilation function indicators VC(vital capacity),FEV1(forced expiratory volume in one second),FEV1% all partly increased but not statistically significant(P > 0.05). In normal ventilation function group,DLCOc/VA was significantly reduced after IMRT(P=0.006,P <0.01)but not in DLCOc-SB(P=0.077). In air resistance indicators,only 3 of them reduced statistically significant,and they were Fres,R5 and R20(P=0.022,P=0.045,P=0.035,respectively).Lung ventilation function indicators VC,FEV1,FEV1% and FEV1/FVC had no statistically significant chang(P>0.05).Conclusions:Intensity modulated conformal radiotherapy(IMRT)can lead to certain diffuse lung function reducing in patients with lung cancer,but can improve the airway resistance in the same time. IMRT had no statistically significant influence in pulmonary ventilation function. Diffuse lung function indicators are more sensitive than all the others and could adopt as a functional sensitivity index to supervise the radiation interstitial pneumonia.