Abstract P1-09-10: Impact of radiation on cardiovascular outcomes in breast cancer patients
Authors: Qin Angel , Silverman Paula , Lyons Janice , Thompson Cheryl L 
Published: May 2015

Background: Radiation therapy is a key component in the treatment of breast cancer. Recent studies have attempted to detail the potential impact that radiation may have on the development of cardiovascular complications in patients with breast cancer. The results of these studies, however, are conflicting regarding the magnitude and clinical significance of the cardiovascular effects with the use of modern radiation techniques. The aim of our study was to examine cardiovascular outcomes in breast cancer patients who received radiation therapy compared to those who did not.

Methods: After IRB approval, all breast cancer patients who received systemic chemotherapy at University Hospitals Case Medical Center between 1998 and 2006 and with known radiation data were included in this retrospective study. A complete patient medical history including risk factors, comorbidities, and tumor and treatment characteristics were obtained from the institutional tumor registry and were confirmed by the medical record. Billing data provided dates of diagnosis for heart failure (HF), coronary artery disease (CAD), and arrhythmia. The patients were divided into three groups: no radiation, right sided radiation, and left sided radiation. The groups were compared to one another and then further subdivided and analyzed based on timing of diagnosis of CAD and HF. Multivariate analyses using a Cox proportional hazards model were conducted for each outcome adjusting for age and comorbidities.

Results: 1277 patients were included in this study with average follow-up of 7.3 years (SD =3.5). CT based planning was used for the majority of the patients. Radiation start dates were not available for 186 patients; these were estimated at 5.5 months after the initiation of chemotherapy. There was no significant difference between groups in the incidences of the cardiovascular outcomes (p&gt;0.05). Further analysis after accounting for timing of diagnosis of CAD and HF showed there was a significantly shorter time to onset of CAD in the left sided radiation group compared to the right sided radiation group; 4.5 years (SD=2.2) compared to 6.5 years (SD=3.6) respectively, p&lt;0.001. However, multivariate analyses were not statistically significant (p=0.47). The onset to HF was shorter in the right sided radiation group compared to the left sided radiation group; 3.5 years (SD 3.1) compared to 4.3 years (SD=3.5) respectively, p&lt;0.001, but again, multivariate analyses were not statistically significant (p=0.43).

Discussion: In our study, we did not find a difference in the incidence of adverse cardiovascular outcomes among patients who did and did not receive radiation, both before and after correcting for timing of diagnosis. We did find a difference in the time to development of these adverse cardiovascular outcomes between the two radiation groups, but no difference was found in either the incidence or time to development when controlled for age and co-morbid conditions. This study suggests that there is little impact of radiation on cardiovascular outcomes using modern techniques that limit radiation exposure. Prospective longitudinal studies focused specifically on cardiac endpoints may be needed to fully understand the cardiovascular impact of radiation.

Citation Format: Angel Qin, Paula Silverman, Janice Lyons, Cheryl L Thompson. Impact of radiation on cardiovascular outcomes in breast cancer patients [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-09-10.