Interobserver Variability of Target Volumes Delineated in the Supine and Prone Positions Based on Computed Tomography Images for External-Beam Partial Breast Irradiation After Breast-Conserving Surgery: A Comparative Study.

Background: Although the supine position remains the dominant position for external-beam partial breast irradiation (EB-PBI), the advantages of administering EB-PBI in the prone position have been recognized. The interobserver variability between target volumes delineated in the different positions for EB-PBI after breast-conserving surgery needs to be investigated. Methods: Twenty-seven patients suitable for EB-PBI were enrolled from July 2016 to April 2017. Supine and prone simulation CT images were sequentially acquired for all enrolled patients during free breathing. Five experienced radiotherapists delineated the target volumes for all patients on supine and prone simulation CT images. The selected parameters, including target volumes, the coefficient of variation (COV), the matching degree (MD), and so on, were calculated to analyze the interobserver variability. Results: Regardless of the patient position, the interobserver variability between tumor bed (TB) and clinical target volume (CTV) measurements in supine and prone positions were statistically significant (F = 31.34, 19.467; 44.000, 41.985; P = 0.000, 0.001; 0.000, 0.001). The interobserver variability of COVCTV was significantly greater in the supine position than in the prone position (T = 2.64, P = 0.014). Furthermore, the interobserver variabilities of MDTB and MDCTV were statistically lower in the supine position than in the prone position (Z = -3.460, -3.195, P = 0.000, 0.001). Conclusion: When delineating the target volume for EB-PBI, the interobserver variability in the prone position was lower than that in the supine position. Hence, the administration of EB-PBI in the prone position during free breathing is a reasonable option.

Setup Error Assessment and Correction in Planar kV Image- Versus Cone Beam CT Image-Guided Radiation Therapy: A Clinical Study of Early Breast Cancer Treated With External Beam Partial Breast Irradiation.

OBJECTIVE: To compare differences in setup error assessment and correction between planar kilovolt images and cone beam computed tomography images for external beam partial breast irradiation during free breathing. METHODS: Nineteen patients who received external beam partial breast irradiation after breast-conserving surgery were recruited. Interfraction setup error was acquired using planar kilovolt images and cone beam computed tomography. After online setup correction, the residual error was calculated, and the setup error was compared. The residual error and setup margin were quantified for planar kilovolt and cone beam computed tomography images. RESULTS: The largest setup error was observed in the anteroposterior direction for both cone beam computed tomography and planar kilovolt imaging (-1.45 mm, 1.74 mm). The cone beam computed tomography-based setup error (systematic error [Σ]) was less than the planar kilovolt images based on Σ in the anteroposterior direction (-1.2 mm vs 2.00 mm; P = .005), and no significant differences were observed for random error (σ) in 3 dimensions ( P = .948, .376, .314). After online setup correction, cone beam computed tomography significantly reduced the residual setup error compared with planar kilovolt images in the anteroposterior direction (Σ: -0.20 mm vs 0.50 mm, P = .008; σ: 0.45 mm vs 1.34 mm, P = .002). The cone beam computed tomography-based setup margin was smaller than the planar kilovolt image-based setup margin in the anteroposterior direction (-1.39 mm vs 5.57 mm, P = .003; 0.00 mm vs 3.20 mm, P = .003). CONCLUSIONS: Discrepancy between the setup errors observed with planar kilovolt and cone beam computed tomography was obvious in the anteroposterior direction. Compared to cone beam computed tomography, the elapsed treatment time was smaller when the initial alignment used kilovolt planar imaging. Whether using planar kilovolt or cone beam computed tomography, residual errors can be reduced to 1.5 mm for external beam partial breast irradiation procedures.

A comparative study based on deformable image registration of the target volumes for external-beam partial breast irradiation defined using preoperative prone magnetic resonance imaging and postoperative prone computed tomography imaging.

BACKGROUND: To explore the differences and correlations between the target volumes defined using preoperative prone diagnostic magnetic resonance imaging (MRI) and postoperative prone computed tomography (CT) simulation imaging based on deformable image registration (DIR) for external-beam partial breast irradiation (EB-PBI) after breast-conserving surgery (BCS). METHODS: Eighteen breast cancer patients suitable for EB-PBI were enrolled. Preoperative prone diagnostic MRI and postoperative prone CT scan sets for all the patients were acquired during free breathing. Target volumes and ipsilateral breast were all contoured by the same radiation oncologist. The gross tumor volume (GTV) delineated on the preoperative MRI images was denoted as the GTVpreMR and the tumor bed (TB) delineated on the postoperative prone CT images was denoted as the GTVpostCT. The MIM software system was used to deformably register the MRI and CT images. RESULTS: When based on the coincidence of the compared target centers, there were statistically significant increases in the conformity index (CI) and degree of inclusion (DI) values for GTVpostCT-GTVpreMR, GTVpostCT-CTVpreMR + 10, CTVpostCT + 10-GTVpreMR, and CTVpostCT + 10-CTVpreMR + 10 when compared with those based on the DIR of the thorax (Z = - 3.724, - 3.724, - 2.591, - 3.593, all P < 0.05; Z = -3.724, - 3.724, - 3.201, - 3.724, all P < 0.05, respectively). CONCLUSIONS: Although based on DIR, there was relatively poor spatial overlap between the preoperative prone diagnostic MRI images and the postoperative prone CT simulation images for either the whole breast or the target volumes. Therefore, it is unreasonable to use preoperative prone diagnostic MRI images to guide postoperative target delineation for EB-PBI.

A comparative study of target volumes based on deformation registration using preoperative prone magnetic resonance imaging and postoperative prone computed tomography imaging for patients undergoing breast-conserving surgery / 中华放射医学与防护杂志

Objective@#To explore the differences and correlation between the target volumes based on deformation registration (DIR) using preoperative prone diagnostic magnetic resonance (MR) imaging and postoperative prone computed tomography (CT) simulation imaging for patients undergoing breast-conserving surgery (BCS).@*Methods@#Eighteen breast cancer patients suitable for external-beam partial breast irradiation (EB-PBI) after BCS were enrolled. Preoperative prone diagnostic MR and postoperative prone CT scan sets were acquired during free breathing for all patients. The gross tumor volume (GTV) delineated on the preoperative diagnostic MR images was defined as GTVMRI, the clinical target volumes (CTVMRI+ 1 and CTVMRI+ 2)were defined as 10 and 20 mm margins around the GTVMRI, and the planning target volume (PTVMRI+ 1 and PTVMRI+ 2) were defined as 15 and 25 mm margins around the GTVMRI, respectively. Tumor bed (TB) delineated on the postoperative prone CT simulation images acquired during free breathing was defined as GTVTB, CTV and PTV were defined as 10 and 15 mm margins around the GTVTB, respectively. The target volume of the whole breast contoured on the MR and CT images were defined as CTVBreast-MRI and CTVBreast-CI, respectively. The MR and CT images were registered deformably in MIM software system.@*Results@#The GTVTB, CTVTB and PTVTB were significantly greater than GTVMRI, GTVMRI+ 1 and PTVMRI+ 1, respectively (Z=-3.593, -3.593, -2.983, P<0.05). Meanwhile, the CTVTB and PTVTB were significantly less than the CTVMRI+ 2 and PTVMRI+ 2, respectively(Z=-2.722, -2.853, P<0.05). The conformal index (CI) and degree of inclusion (DI) of GTVTB-GTVMRI, GTVTB-CTVMRI+ 1, CTVTB-GTVMRI and CTVTB-GTVMRI+ 1 based on center-coincidence of the compared targets were better than those based on DIR of the thorax(Z=-3.724、-3.724、-2.591、-3.593, P<0.05; Z=-3.724、-3.724、-3.201、-3.724, P<0.05).@*Conclusions@#For the patients enrolled for prone EB-PBI, target volumes delineated on the preoperative prone MR images were significantly smaller compared to that on the postoperative prone CT images, but a statistically significant positive correlation was found between the MR and CT target volumes. There were still relatively poor spatial overlap whether for the whole breast or the targets between the preoperative prone diagnostic MR images and the postoperative prone simulation CT images based on DIR. Therefore, it is infeasible to guide postoperative EB-PBI target delineation using the preoperative prone diagnostic MR images.

A comparison of dosimetric variance for external-beam partial breast irradiation using three-dimensional and four-dimensional computed tomography / 中华肿瘤杂志

Objective@#To investigate the potential dosimetric benefits of four-dimensional computed tomography (4DCT) compared to three-dimensional CT (3DCT) in the planning of radiotherapy for external-beam partial breast irradiation (EB-PBI).@*Methods@#Three-DCT and 4DCT scan sets were acquired for 20 patients who underwent EB-PBI. For each patient a conventional 3D conformal plan (3D-CRT) was generated based on end-inhalation phase (EI). The treatment plan based on the 4DCT EI phase images was copied and applied to the end-exhalation phase (EE) and 3DCT images (defined as EB-PBIEI, EB-PBIEE, EB-PBI3D, respectively).@*Results@#The median volumes of the tumour bed based on 3DCT, EI and EE were 20.99 cm3, 19.28 cm3, and 18.78 cm3, respectively. The tumour bed volume based on 3DCT was significantly greater than that of EI and EE volumes (P<0.05). The planning target volumes (PTV) coverage of EB-PBI3D, EB-PBIEI and EB-PBIEE were 96.85%, 97.51%, 97.03%, respectively. The planning target volume (PTV) coverage of EB-PBI3D was significantly less than that of EB-PBIEI and EB-PBIEE (P<0.05). The median homogeneity indexs (HI) based on 3DCT, EI and EE were 0.13, 0.13, 0.13, respectively. The median conformal indexs (CI) based on 3DCT, EI and EE were 0.68, 0.69, 0.68, respectively. The median mean doses (Dmean) based on 3DCT, EI and EE were 36.20 Gy, 36.20 Gy, 36.22 Gy, respectively. However there were no significant differences in the homogeneity index, conformity index and the mean dose of PTV between the three treatment plans (P>0.05). The EB-PBI3D plan resulted in the largest organs at risk dose (P<0.05).@*Conclusion@#There was a significant benefit when using 4DCT to plan 3D-CRT for EB-PBI with regard to reduced non-target organ exposure, and might result in poor dose coverage when the PTV is determined using 3DCT.

A comparison of dosimetric variance for external-beam partial breast irradiation using three-dimensional and four-dimensional computed tomography.

PURPOSE: To investigate the potential dosimetric benefits from four-dimensional computed tomography (4DCT) compared with three-dimensional computed tomography (3DCT) in radiotherapy treatment planning for external-beam partial breast irradiation (EB-PBI). PATIENTS AND METHODS: 3DCT and 4DCT scan sets were acquired for 20 patients who underwent EB-PBI. The volume of the tumor bed (TB) was determined based on seroma or surgical clips on 3DCT images (defined as TB3D) and the end inhalation (EI) and end exhalation (EE) phases of 4DCT images (defined as TBEI and TBEE, respectively). The clinical target volume (CTV) consisted of the TB plus a 1.0 cm margin. The planning target volume (PTV) was the CTV plus 0.5 cm (defined as PTV3D, PTVEI, and PTVEE). For each patient, a conventional 3D conformal plan (3D-CRT) was generated (defined as EB-PBI3D, EB-PBIEI, and EB-PBIEE). RESULTS: The PTV3D, PTVEI, and PTVEE were similar (P=0.549), but the PTV coverage of EB-PBI3D was significantly less than that of EB-PBIEI or EB-PBIEE (P=0.001 and P=0.025, respectively). There were no significant differences in the homogeneity or conformity indexes between the three treatment plans (P=0.125 and P=0.536, respectively). The EB-PBI3D plan resulted in the largest organs at risk dose. CONCLUSION: There was a significant benefit for patients when using 3D-CRT based on 4DCT for EB-PBI with regard to reducing nontarget organ exposure. Respiratory motion did not affect the dosimetric distribution during free breathing, but might result in poor dose coverage when the PTV is determined using 3DCT.

The impact of respiratory motion for target dose during external-beam partial breast irradiation / 中华放射医学与防护杂志

Objective To evaluate the impact of respiratory motion for dose of target and organ at risk during external-beam partial breast irradiation (EB-PBI).Methods 4D-CT scan sets were acquired for 20 patients who underwent EB-PBI.The volume of the tumour bed (TB) was determined based on seroma or surgical clips on the ten sets of 4D-CT images.For each patient a conventional 3D conformal plan (3D-CRT) was generated based on the 4D-CT end inhalation phase images,then copied and applied to the other phases.The following parameters were calculated to analyse:mean dose (D),homogeneity index (HI),conformal index (CI),and the volumes that received ≥ x Gy (Vx).Results During free breathing,the TB centroid motion was 0.90,0.75 and 0.80 mm in the lateral,anteroposterior and superior-inferior directions,respectively.The medium spatial motion vector was 0.95 mm.In the superiorinferior direction,TB motion significantly correlated with D HI,and CI of PTV (r =-0.458,-0.451 and 0.462,P ＜ 0.05),as well as D V20 and V30 received by the ipsilateral normal breast (r=0.527,0.488 and0.526,P ＜0.05).And in the motion vector,the D V5,V10,V20 of the ipsilateral lung all correlated with TB motion (r =0.416,0.503,0.522 and 0.498,P ＜ 0.05).A correlation also existed between dose and percent volume of heart and volume variation of heart (Dmean,V5 and V10) (r =0.727,0.704 and 0.695,P ＜ 0.05).Conclusions Small TB motion caused by respiratory motion during free breathing result in dosimetric variation of the target and potential dosimetric off-target or suboptimal dose coverage for EB-PBI.The doses of lung during free breathing were relatively sensitive to TB motion and thorax expansion,while heart doses were not influenced notably.

Dosimetric effects of target volume delineation with metal clip and seroma, alone or in combination, on external-beam partial breast irradiation :a study based on four-dimensional computed tomography / 中华放射肿瘤学杂志

Objective To evaluate the dosimetric effects of target volume delineation with metal clip and seroma,alone or in combination,on external-beam partial breast irradiation (EB-PBI) based on four-dimensional computed tomography (4DCT).Methods Twenty female patients undergoing EB-PBI from 2009 to 2013 were enrolled as subjects.The gross tumor volumes (GTVs),GTVC,GTVS,and GTVC+S,were delineated on 4DCT images at 10 phases using metal clip,seroma,and both of them,respectively.The GTVS on 4DCT images at 10 phases were fused to generate the internal gross tumor volumes (IGTVS),IGTVC,IGTVS,and IGTVC+S.The planning target volumes (PTVS),PTVC,PTVS,and PTVC+S,were obtained via expansion of margin by 15 mm.The three-dimensional conformal radiotherapy plans were made by one physician based on PTVC,PTVS,and PTVC+S on end-inhalation images.The target volume,homogeneity index (HI),conformity index (CI),and doses to organs at risk were compared between the three groups.Results The C+S group had the largest IGTV,PTV,and the ratio of PTV to diseased breast volume,which was followed by the C group and the S group (all P＜ 0.05).The S group had significantly lower doses to the ipsilateral normal breast and lung than the C group and the C+S group (all P＜0.05).There were no significant differences in HI or CI between the three groups (all P＞ 0.05).Conclusions The volume variation caused by target volume dehneation on 4DCT images based on different references has little impact on dose distribution in target volume.However,it has substantial impact on radiation doses to the ipsilateral normal breast and lung.

Dosimetric impact of tumor bed delineation variability based on 4DCT scan for external-beam partial breast irradiation.

This study sought to evaluate the dosimetric impact of tumor bed delineation variability (based on clips, seroma or both clips and seroma) during external-beam partial breast irradiation (EB-PBI) planned utilizing four-dimensional computed tomography (4DCT) scans. 4DCT scans of 20 patients with a seroma clarity score (SCS) 3~5 and ≥5 surgical clips were included in this study. The combined volume of the tumor bed formed using clips, seroma, or both clips and seroma on the 10 phases of 4DCT was defined as the internal gross target volume (termed IGTVC, IGTVS and IGTVC+S, respectively). A 1.5-cm margin was added by defining the planning target volume (termed PTVC, PTVS and PTVC+S, respectively). Three treatment plans were established using the 4DCT images (termed EB-PBIC, EB-PBIS, EB-PBIC+S, respectively). The results showed that the volume of IGTVC+S was significantly larger than that of IGTVCand IGTVS. Similarly, the volume of PTVC+S was markedly larger than that of PTVC and PTVS. However, the PTV coverage for EB-PBIC+S was similar to that of EB-PBIC and EB-PBIS, and there were no significant differences in the homogeneity index or conformity index between the three treatment plans (P=0.878, 0.086). The EB-PBIS plan resulted in the lowest ipsilateral normal breast and ipsilateral lung doses compared with the EB-PBIC and EB-PBIC+S plans. To conclude, the volume variability delineated based on clips, seroma or both clips and seroma resulted in dosimetric variability for organs at risk, but did not show a marked influence on the dosimetric distribution.

When is respiratory management necessary for partial breast intensity modulated radiotherapy: a respiratory amplitude escalation treatment planning study.

PURPOSE: The impact of typical respiratory motion amplitudes (∼2 mm) on partial breast irradiation (PBI) is minimal; however, some patients have larger respiratory amplitudes that may negatively affect dose homogeneity. Here we determine at what amplitude respiratory management may be required to maintain plan quality. METHODS AND MATERIALS: Ten patients were planned with PBI IMRT. Respiratory motion (2-20 mm amplitude) probability density functions were convolved with static plan fluence to estimate the delivered dose. Evaluation metrics included target coverage, ipsilateral breast hotspot, homogeneity, and uniformity indices. RESULTS: Degradation of dose homogeneity was the limiting factor in reduction of plan quality due to respiratory motion, not loss of coverage. Hotspot increases were observed even at typical motion amplitudes. At 2 and 5 mm, 2/10 plans had a hotspot greater than 107% and at 10 mm this increased to 5/10 plans. Target coverage was only compromised at larger amplitudes: 5/10 plans did not meet coverage criteria at 15 mm amplitude and no plans met minimum coverage at 20 mm. CONCLUSIONS: We recommend that if respiratory amplitude is greater than 10 mm, respiratory management or alternative radiotherapy should be considered due to an increase in the hotspot in the ipsilateral breast and a decrease in dose homogeneity.

Radioterapia externa parcial acelerada en pacientes con cáncer de seno en estado temprano / External Beam Partial Breast Irradiation for Early Breast Cancer

Objetivo: Demostrar la eficacia y efectividad de la radioterapia parcial acelerada en cáncer temprano de mama en pacientes tratadas con cirugía conservativa. Método: Se trataron cien mujeres con radioterapia externa parcial acelerada, con dosis en un rango de 35 a 38,5 Gy, en 10 fracciones en 5 días dos veces al día con un intervalo de 6 horas. Todas se trataron con 4 campos no cooplanares. El volumen tumoral clínico estuvo cubierto de forma homogénea con la isodosis del 100 %; así mismo el volumen de planeación del blanco, incluido en la isodosis del 95 %. Resultados: El seguimiento promedio fue de 54,3 meses. La tolerancia al tratamiento fue buena y ninguna mujer presentó toxicidad grado 2 o 3. Hasta el momento una paciente presentó recaída ganglionar, local y a distancia. Conclusión: El tratamiento fue bien tolerado, con toxicidad baja y con buenos resultados, en un tiempo corto, con posibles beneficios económicos especialmente en la población de países en vías de desarrollo...

Objective: In this study, our purpose was todemonstrate the feasibility and effectiveness ofexternal beam partial breast irradiation (PBI) inpatients with early-stage breast cancer treated withbreast-conserving surgery. Methods: 100 patientswere treated with PBI with doses ranging from 35to 38.5 Gy, in 10 fractions b.i.d. All patients weretreated with four non-coplanar fields. The clinicaltumor volume was well encompassed withinthe isodose line of 100 % as well as the planningtarget volume which was within the isodose lineof 95 %. Results: The median follow-up was of54.3 months. The treatment was well tolerated,with no more than grade I toxicity. So far, therehas been one patient with local and axillar recurrence.Conclusions: In our experience, thetreatment was well tolerated with low toxicityand with good results, in a shorter treatment time,with the economical benefits this has, especiallyfor populations in developing countries...

Comparison of displacement of the geometry constituted by silver clips in cavity in the different state of respiration assisted by active breathing control system in external-beam partial breast irradiation / 中华放射肿瘤学杂志

ObjectiveTo investigate the effect of the displacement of the selected silver clip in the different respiratory state achieved by active breathing control ( ABC ) system on the displacement of the geometry constituted by all of the silver clips at the border of the cavity in external-beam partial breast irradiation (EB-PBI).MethodsTwo sets of CT images in state of moderate deep inspiratory breathing hold (mDIBH),deep expiratory breathing hold (DEBH),and free breath (FB) were acquired in the same CT simulation assisted by ABC system for each of the 27 patients after breast conservative surgery.All silver clips in the cavity were delineated based on each set of CT images.Thereafter,the irregular geometry based on the silver clips as the vertices was automatically formed.Four selected clips located at the top,bottom,lateral border and medial border of the cavity were correspondingly manually registered based on automatic registration of the CT images acquired in the same or different state of respiration including mDIBH,FB,and DEBH.The displacement of center of the geometry in the direction of right-left (RL),anterior-posterior (AP),and superior-inferior (SI) separately based on automatic registration and manual registration was evaluated.The difference of the displacement was analyzed by Kruskal-Wallis H-test and Kolmogorov-Smirnov Z-test.Results When registered between mDIBH and mDIBH,FB and FB,DEBH and DEBH,the differences of the displacement of the center of geometry were not statistically significant (H =0.00 - 1.76,P=0.184-0.954). When registered between mDIBH and DEBH,the differences were statistically significant ( Z =11.31 - 23.00,P =0.000 - 0.001 ).There were statistically significant differences in the displacement of geometry center based on the selected silver clip between different registration forms in AP and SI directions (Z=4.76-25.54,P=0.000-0.029).ConclusionsThe difference of intrafraction displacement of the geometry constituted by the clips between the same respiratory states in the three dimensional direction is not statistically significant,but the difference is statistically significant between the different respiratory states in AP and SI directions.

Dosimetric comparison of three-dimensional conformal radiotherapy,intensity-modulated radiotherapy and volumetric modulated arc radiotherapy in partial breast irradiation / 中华放射医学与防护杂志

Objective To compare the dosimetric differences of three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and volumetric modulated arc radiotherapy(V-MAT) for external beam partial breast irradiation.Methods Twelve patients with breast cancer receiving breast-conserving surgery and external beam partial breast irradiation were enrolled.Three different techniques including 3D-CRT,IMRT and V-MAT were designed for each patient.The dosimetry in the target,the dose to the organs at risk(OAR),the MU and delivery time were compared.Results All three plans met the clinical requirement. 3D-CRT showed the worst conformity in target. V-MAT provided the lowest target coverage and homogeneity in target.3D-CRT plans showed the lowest values for the V5,V10,mean dose and the highest values for V30 in the ipsilateral lung.No statistically significant differences were observed in V20 of the ipsilateral lung among three plans.V-MAT showed the lowest values in ipsilateral normal breast volume 15,20 and 25 Gy post-irradiation.For V5,the mean and max dose in heart,the mean dose in contralateral lung and the mean,max dose in thyroid,IMRT and 3D-CRT showed the highest and lowest value respectively(z =-2.94 - -2.09,P ＜ 0.05 ).The MUs in 3D-CRT,IMRT and V-MAT were 417.6 ± 34.4,772.8 ± 54.4 and 631.0 ± 109.0,respectively (z =- 2.93, - 2.76,-2.93,P ＜ 0.05 ). V-MAT significantly reduced the delivery time. Conclusions V-MAT shows significant advantages in reducing the dose in the ipsilateral normal breast and the delivery time compared with 3D-CRT and IMRT.