The Left Side Of Breast Cancer After Radiotherapy In Patients With Heart Main Sub-structure Outlined And The Physical Dose And Biological Dose Radiotherapy

Partâ… Delineation of the cardiac sub-structures based on PET-CT and contrast enhanced CT in patients with left-sided breast cancer treated with post-operative radiotherapyPurpose:To evaluate and compare the discrimination of volume between contrast enhanced CT-based left ventricle(LV) and PET-CT-based LV in left-sided breast cancer patients treated with adjuvant radiotherapy.To assess the impact of dose and volume in interrelations for heart and cardiac sub-structures using dose-volume histograms.Material and methods:From October 2008 to February 2009,14 patients with post-operatively confirmed left-sided breast cancer were enrolled in this study. Patients were scanned using contrast enhanced CT for simulation and ¹⁸F-FDG PET-CT were applied to display the structure of left ventricle in each patient before radiotherapy(RT).The LV was delineated based on both contrast enhanced CT and PET-CT.Other critical sub-structures,such as left anterior descending coronary artery(LAD) were contoured in each patient.The six-field simple intensity modulated radiotherapy(sIMRT) technique were created in all patients.Results:The mean volumes of left ventricle based on contrast enhanced CT (LV-CT) and PET-CT(LV-PET) were 107.296 cm³ and 112.931 cm³,respectively (p=0.06).The volume of LV receiving≥50%prescription dose highly correlated with the volume of heart receiving≥50%prescription dose(γ=0.869).Less correlation between the volume of LAD and the volume of heart receiving≥50% prescription dose was observed(γ=0.22).Conclusion:The left ventricle could be delineated efficiently based on imaging of PET-CT.Moreover,the contrast enhanced CT based LV could be an appropriate substitute in contouring LV for left-sided breast cancer patients.The volume of LV receiving higher dose in RT has high correlation with the volume of heart using sIMRT technique.It may pave the way for further exploring radiation induced cardiac injury in patients with breast cancer. Partâ…¡Estimating cardiac sub-structures exposure from diverse radiotherapy techniques in treating left-sided breast cancer patientsPurpose:To compare intensity-modulated radiotherapy(IMRT) plans to plans created by 3D-planned tangent fields using variety parameters derived from dose-volume histograms in predicting the dose and biologically effective dose(BED) to the heart and the cardiac sub-structures for left-tangential breast or chest wall irradiation.Material and methods:For 14 computed tomography data sets of patients with left-sided breast cancer,a 3D treatment plan(3D-CRT),a six-field IMRT plan(IMRT) and a six-field simple IMRT plan(sIMRT) were created.BED to the critical organs and subunits in heart has been calculated and converted from physical dose using BED calculation formula based on L-Q model.Results:IMRT and sIMRT reduced the average maximal dose to heart(50.38Gy vs 53.46Gy)(p＜0.05),and IMRT reduced 4%of average maximal dose to the LV (p=0.054) in comparison with 3D-CRT.The average heart volume receiving≥50% prescription dose in IMRT,sIMRT and 3D-CRT were 73.98 cm³,76.75 cm³and 60.34 cm³,respectively.The average LV volume receiving≥50%prescription dose in IMRT,sIMRT and 3D-CRT were 23.37 cm³,24.68 cm³ and 17.61 cm³,respectively. BED to the critical subunits which located in high physical dose area was substantially lower in IMRT in comparison with 3D-CRT or sIMRT.Conclusion:IMRT for left-sided breast cancer significantly reduced the maximal dose to the heart and left ventricle,which might translate into reduced cardiac mortality.The calculation of BED could be extrapolated to predict and assess the long-term risk of radiation induced cardiac toxicity.