Cardiac Structure Doses in Women Irradiated for Breast Cancer in the Past and Their Use in Epidemiological Studies

Abstract

Purpose Incidental cardiac exposure during radiation therapy may cause heart disease. Dose-response relationships for cardiac structures (segments) may show which ones are most sensitive to radiation. Radiation-related cardiac injury can take years to develop; thus, studies need to involve women treated using 2-dimensional planning, with segment doses estimated using a typical computed tomography (CT) scan. We assessed whether such segment doses are accurate enough to use in dose-response relationships using the radiation therapy charts of women with known segment injury. We estimated interregimen and interpatient segment dose variability and segment dose correlations. Methods and Materials The radiation therapy charts of 470 women with cardiac segment injury after breast cancer radiation therapy were examined, and 41 regimens were identified. Regimens were reconstructed on a typical CT scan. Doses were estimated for 5 left ventricle (LV) and 10 coronary artery segments. Correlations between cardiac segments were estimated. Interpatient dose variation was assessed in 10 randomly selected CT scans for left regimens and in 5 for right regimens. Results For the typical CT scan, interregimen segment dose variation was substantial (range, LV segments <1-39 Gy; coronary artery segments <1-48 Gy). In 10 CT scans, interpatient segment dose variation was higher for segments near field borders (range, 3-47 Gy) than other segments (range, <2 Gy). Doses to different left-anterior descending coronary artery (LADCA) segments were highly correlated with each other, as were doses to different LV segments. Also, LADCA segment doses were highly correlated with doses to LV segments usually supplied by the LADCA. For individual regimens there was consistency in hotspot location and segment ranking of higher-versus-lower dose. Conclusions The scope for developing quantitative cardiac segment dose-response relationships in patients who had 2-dimensional planning is limited because different segment doses are often highly correlated, and segment-specific dose uncertainties are not independent of each other. However, segment-specific doses may be reliably used to rank segments according to higher-versus-lower doses.

Exposure of the heart and cardiac valves in women irradiated for breast cancer 1970–2009

“…A “typical CT-scan” was selected by reconstructing commonly-used regimens on ten CT-scans randomly selected from the radiotherapy database of women irradiated in 2010. The CT-dataset that was typical for heart dose, and did not have unusual anatomy, was selected as the “typical CT-scan” [20] , [22] . The treatment position was supine, with both arms above the head.…”

Radiobiological models in prediction of radiation cardiotoxicity

“…Nevertheless, studies by Duane et al, and McGale et al indicate an increase in the risk of chronic pericarditis in patients after left breast radiotherapy 1.6 times compared to the group treated for right cancer. 27,28 The latest epidemiological data indicate that radiation-induced cardiomyopathy, RICM, occurs, on average, after 40 years following the end of treatment in nearly 25 % of patients, although the majority of these cases are induced by heart damage (valvular disease or myocardial infarction). Statistically, the risk of symptoms increases after five years from the end of therapy but may evolve many years later.…”

Heart atlas for retrospective cardiac dosimetry: a multi-institutional study on interobserver contouring variations and their dosimetric impact

“…Better survival mandates a focus on long-term adverse treatment effects which can affect more patients. Aside from potentially cardiotoxic chemotherapy and anti-HER2 immunotherapy [ 4 ], breast cancer RT can expose the heart to high levels of radiation [ 5 , 6 ]. The need to address late cardiac effects of breast cancer treatment is now widely recognized [ 4 , 7 ].…”