Tomorrow's targeted therapies in breast cancer patients: what is the risk for increased radiation-induced cardiac toxicity?

Ongoing clinical trials are now investigating the benefits of new targeted therapies, including ErbB and tyrosine kinase inhibitors (TKI) and antiangiogenics. Those may carry a potential risk for additional cardiac toxicity, particularly in association with radiotherapy. Although the risk of symptomatic cardiotoxicity is low, more subtle functional declines may increase mortality with longer follow-up and necessitate caution when assessing concurrent or sequential trastuzumab or lapatinib with radiotherapy. Potential additive toxicity encourages more conformal irradiation modalities minimizing cardiac dose, such as gating, intensity-modulated radiotherapy or Helical Tomotherapy. We recommend the collection of substantial information relevant to cardiac radiotoxicity in further clinical trials of targeted agents in breast cancer treatment, including doses delivered to cardiac structures, especially the coronary arteries. The incorporation of new biomarkers or modalities for assessment of cardiac function may also become necessary to detect cardiac toxicity at earliest stage.