ABSTRACT
Purpose A relationship between mean heart dose (MHD) and acute coronary event (ACE) rate was reported in a study of patients with breast cancer (BC). The main objective of our cohort study was to validate this relationship and investigate if other dose-distribution parameters are better predictors for ACEs than MHD. Patients and Methods The cohort consisted of 910 consecutive female patients with BC treated with radiotherapy (RT) after breast-conserving surgery. The primary end point was cumulative incidence of ACEs within 9 years of follow-up. Both MHD and various dose-distribution parameters of the cardiac substructures were collected from three-dimensional computed tomography planning data. Results The median MHD was 2.37 Gy (range, 0.51 to 15.25 Gy). The median follow-up time was 7.6 years (range, 0.1 to 10.1 years), during which 30 patients experienced an ACE. The cumulative incidence of ACE increased by 16.5% per Gy (95% CI, 0.6 to 35.0; P = .042). Analysis showed that the volume of the left ventricle receiving 5 Gy (LV-V5) was the most important prognostic dose-volume parameter. The most optimal multivariable normal tissue complication probability model for ACEs consisted of LV-V5, age, and weighted ACE risk score per patient (c-statistic, 0.83; 95% CI, 0.75 to 0.91). Conclusion A significant dose-effect relationship was found for ACEs within 9 years after RT. Using MHD, the relative increase per Gy was similar to that reported in the previous study. In addition, LV-V5 seemed to be a better predictor for ACEs than MHD. This study confirms the importance of reducing exposure of the heart to radiation to avoid excess risk of ACEs after radiotherapy for BC.
Subject(s)
Breast Neoplasms/radiotherapy , Heart/radiation effects , Myocardial Infarction/epidemiology , Radiation Dosage , Adolescent , Adult , Age Factors , Aged , Breast Neoplasms/surgery , Dose-Response Relationship, Radiation , Female , Follow-Up Studies , Heart Ventricles/radiation effects , Humans , Imaging, Three-Dimensional , Incidence , Mastectomy, Segmental , Middle Aged , Myocardial Ischemia/mortality , Percutaneous Coronary Intervention/statistics & numerical data , Probability , Proportional Hazards Models , Radiotherapy Planning, Computer-Assisted , Risk Assessment/methods , Risk Factors , Tomography, X-Ray Computed , Young AdultABSTRACT
BACKGROUND AND PURPOSE: To develop a method based on electronic portal images (EPIs) for the position verification of breast cancer patients that are treated with a simultaneous integrated boost (SIB) technique. METHOD: 3D setup errors of the breast outline and the thoracic wall were determined from EPIs of the tangential treatment fields and anterior posterior (AP) verification field. The method was verified with repeated CT scans of 38 patients with an average setup error larger than 5 mm. RESULT: The 3D position deviation of the boost volume can best be determined from the position deviation of the breast outline in the ventrodorsal direction and the thoracic wall in the lateral and longitudinal directions from the tangential and AP EPIs. The method gives an average overestimation of the deviation of the boost volume in the ventrodorsal, lateral and longitudinal directions by 28%, 20% and 6%, respectively and an average underestimation of the deviation of the whole breast by 32%, 17% and 39%. CONCLUSIONS: The described method is superior to using tangential EPIs only and is recommended for position verification of breast cancer patients that are treated with a SIB technique if no Cone beam CT (CBCT) or fiducial markers can be used.
