No Association Between Left-Breast Radiation Therapy or Breast Arterial Calcification and Long-Term Cardiac Events in Patients with Breast Cancer

BACKGROUND: Recent studies have suggested an association between radiation therapy (RT) of the left breast and increased incidence of coronary artery disease. However, the increased sparing afforded with modern RT may decrease long-term cardiac risk. The aims of our study were to evaluate the association between the RT and cardiac events in breast cancer patients who underwent contemporary RT and to examine whether breast arterial calcification (BAC) seen on mammogram predicts for cardiac events. METHODS AND MATERIALS: In our observational, descriptive pilot study, 2,439 patients with breast cancer between 1986 and 2007 and a minimum of 3 years since completing RT were asked to complete a questionnaire regarding cardiac events since RT completion. The preoperative and follow-up mammograms were coded for presence/absence of BAC by an experienced radiologist blinded to questionnaire results. Cardiac events were compared between patients who received left- and right-sided adjuvant radiation. RESULTS: At a mean follow-up of 7.5 years (range 3-24), 687 patients completed the questionnaire, with 602 eligible for analysis. Baseline characteristics (age, body mass index [BMI], surgery type, cardiovascular risk factors, and time since RT) were similar in patients who received left- versus right-sided RT. Hypertension before RT and during follow-up, baseline cardiovascular disease, age >50, BMI >30 kg/m², and subsequent development of diabetes were significantly associated with posttreatment cardiac events. BACs were associated with cardiac events reported before breast cancer diagnosis; however, no association was found between left-sided breast RT or BAC and subsequent cardiac events. CONCLUSION: In a large single-institutional observational study, no association was found between left-sided breast RT or BAC and subsequent cardiac events.