Radiation Dose and Cardiac Risk in Breast Cancer Treatment: An Analysis of Modern Radiotherapy Including Community Settings

Publication date: Available online 20 July 2017
Source:Practical Radiation Oncology
Author(s): Julian C. Hong, Elham Rahimy, Cary P. Gross, Timothy Shafman, Xin Hu, James B. Yu, Rudi Ross, Steven E. Finkelstein, Arie Dosoretz, Henry S. Park, Pamela R. Soulos, Suzanne B. Evans
PurposeAdjuvant radiotherapy (RT) for breast cancer improves outcomes, but prior studies have documented substantive cardiac dose and cardiac risk. We assessed mean heart dose (MHD) of RT, and estimated risk of RT-associated cardiac toxicity in women undergoing adjuvant RT for breast cancer in contemporary (predominantly) community practice.Methods and MaterialsWe identified women with left-sided breast cancer receiving adjuvant RT during 2012 through 2014 from 94 centers across 16 states. We used bivariate analyses and multivariable linear regression to assess associations between RT techniques and MHD. Excess RT-related cardiac risk by age 80 was estimated for women diagnosed at age 60 using previously reported relationship between MHD and cardiac risk.ResultsAmong 1161 women, 77.3% were treated in community practice and with breast-conservation (77.8%). The most common techniques were free-breathing (92.2%), supine (94.8%), and fixed gantry intensity modulated RT (FG-IMRT; 46.9%). Median MHD was 2.76Gy (IQR 1.47–5.03). In multivariable analyses, predicted median MHD with deep inspiration breath hold was 2.41Gy compared to 3.86Gy with free-breathing (p<0.001). Three-dimensional conformal RT (3D–CRT) was associated with lower predicted median MHD (2.78Gy) than FG-IMRT (4.02Gy) or rotational IMRT (R-IMRT, 6.60Gy, p<0.001). For 60-year old women with the median MHD of the study population (2.76Gy) and no cardiovascular risk factors, the 20-year predicted excess risk of death from ischemic heart disease attributable to radiation was 3.5 excess events/1000 patients, in contrast to estimates of 8 events/1000 from prior analyses. The predicted risk of cardiac events varied based on radiation technique, with 4 excess events/1000 with 3D–CRT, 5 excess events/1000 with FG-IMRT, and 8 excess events/1000 with R-IMRT.ConclusionsMHD varies substantially across patients and is influenced by technique in predominantly community settings. Overall risk of cardiac toxicity is modest.SummaryWe assessed mean heart dose of radiotherapy (RT), and estimated risk of RT-associated cardiac toxicity in women undergoing adjuvant RT for left-sided breast cancer in a large contemporary cohort. For 60-year old women without cardiovascular risk factors, the predicted excess risk of death from ischemic heart disease 20years post-radiation was 3.5 excess events/1000 patients, lower than estimates derived in prior studies (8 per 1000). Mean heart dose varied substantially and was influenced by technique.



http://ift.tt/2uPaKsL