Prevalence of poor cardiac anatomy in carcinoma of the breast treated with whole-breast radiotherapy: reconciling modern cardiac dosimetry with cardiac mortality data
Department of Radiation Oncology
Adult; Aged; Aged, 80 and over; Body Mass Index; Breast; Breast Neoplasms; Carcinoma; Coronary Artery Disease; Female; Heart; Humans; Middle Aged; Multivariate Analysis; Organ Size; Radiation Injuries; Radiotherapy Dosage
Neoplasms | Oncology
PURPOSE: : The purpose of the study was to identify patient characteristics that predict for increased cardiac exposure through dosimetric analysis of the anatomy of a cohort of women treated with left-sided tangential breast radiation. Statistical analyses estimations for the appropriate sample sizes required for detection of significant differences in cardiac mortality at 15 years were conducted, assuming a threshold V25 for radiation-induced coronary artery disease (CAD) beyond which women are at risk for radiation-induced coronary artery disease.
METHODS AND MATERIALS: : Detailed heart dosimetry was recorded. Clinical factors (age, history of CAD, diabetes, receipt of cardiotoxic agents, weight/body mass index) and anatomic factors (heart volume, breast volume, cardiac contact distance) were recorded for each patient.
RESULTS: : The average heart V25 was 3.57%. The median percentage of the heart included in the tangential beam was 4.02%. There were no clinical or anatomic factors that predict suboptimal heart anatomy (ie, V25 of >/=6%) on multivariate analysis. The sample size calculations using thresholds for induction of CAD of V25 >/=1%, 6%, and 10% yielded sample sizes of 1314, 9504, and 61,342, respectively; considering node-positive breast cancer mortality and 15% loss to follow-up, these change to 2237, 16,166, and 104,334, respectively.
CONCLUSIONS: : Current studies with modern radiotherapy techniques would be underpowered to detect a difference in cardiac mortality where only some women are at risk. The heart, chest wall, and breast have a complex relationship to tangential breast radiation, and their interplay prevented this anatomic metric's success.
DOI of Published Version
Am J Clin Oncol. 2012 Dec;35(6):587-92. doi: 10.1097/COC.0b013e31822d9cf6. Link to article on publisher's site
American journal of clinical oncology
Evans SB, Sioshansi S, Moran MS, Hiatt J, Price LL, Wazer DE. (2012). Prevalence of poor cardiac anatomy in carcinoma of the breast treated with whole-breast radiotherapy: reconciling modern cardiac dosimetry with cardiac mortality data. Radiation Oncology Publications. https://doi.org/10.1097/COC.0b013e31822d9cf6. Retrieved from https://escholarship.umassmed.edu/radiationoncology_pubs/15