Clinical Application Of Optical Surface Monitoring System In Radiotherapy For Breast Cancer

ObjectivesOur research was divided into two parts.The first part aims to investigate the precision and stability of optical surface monitoring system(OSMS)in guiding radiotherapy positioning compared with traditional laser-based positioning.In the second part,we reported the experience of our single institution with organs at risk(OARs)-sparing radiotherapy(RT)with deep inspiration breath hold(DIBH)using OSMS in left breast conservative patients and compare the dosimetric parameters with that of free breathing(FB).Besides,we constructed a controlled trail evaluating the influence of DIBH on cardiac function and complications over patients with the use of FB.In addition,predictors of cardiac exposure were assessed to better select patients for DIBH.MethodsWe performed a prospective single-institution research.In the first part,twenty-six patients with left-sided breast cancer were collected from October 2020 to February 2021.All patients were divided into control group(13 cases)and the experimental group(13 cases),using traditional positioning and OSMS positioning,respectively.The errors between two groups were recorded and compared using the t test analysis after cone-beam computed tomography(CBCT)verification.At the same time,the correlation between OSMS and CBCT values was assessed by Pearson correlation analysis.In the second part of the research,ten cases(group DIBH)diagnosed as early stage left-sided breast cancer scheduled for postoperative fixed field intensity-modulated radiation therapy(FF-IMRT)with the use of DIBH were enrolled from February 2021 to April 2021.The dosimetric analysis of the heart,left anterior descending(LAD)coronary artery,lungs were performed under FB and DIBH plans.Meanwhile,the anatomical parameters cardiac contacting distance(CCD)and heart-to-chest distance(HCD)were introduced and the correlation with cardiac dose was assessed.In addition,another ten cases underwent FF-IMRT in the state of FB were enrolled as control group(group FB)compared with group DIBH.The quantified cardiac function within and between the two groups were analysed.ResultsA dataset of 165 CBCT values were collected in the frrst part of the research.Compared with traditional positioning,OSMS positioning reduced the system deviation in three translation directions(VRT,LNG and LAT)by 0.1 cm,0.01cm and 0.17cm.There is no significant difference in LAT.Random deviations are also reduced in most directions,and the reduction ratios are.21%(VRT),35%(LNG),29%(LAT),63%(Pitch)and 25%(Yaw),respectively.In the second part of the research,the mean value of DIBH positioning for 10 cases were within lmm/1°.Compared with FB plan,DIBH resulted in significantly changed in the average mean Heart dose(P=0.004)and volumes to the heart receiving irradiation dose.Significant were differences for all cardiac structures.There was 9.7%reduction of V5(P=0.000)and 6.2%reduction of V25(P=0.009).For LAD,we found significantly reduced maximum radiation dose of 16.5Gy(P=0.001)and 14.4%reduction of V40.FB-CCDps and FB-HCD are two potentially good predictors for cardiac exposure and the mean heart dose reduction.Compare with another ten cases of Group FB,there were no significant differences in cardiac function before and after radiotherapy(P>0.05).ConclusionsOSMS is an effective technology that may allow easier-to-achieve precise positioning compared with traditional positioning.Meanwhile,compared with FB,DIBH was characterized by lower doses to OARs,which may reduce the probability of cardiac and pulmonary complications in the future.FB-CCDps and FB-HCD are two potentially good predictors for cardiac exposure.