In this large Canadian population-based cohort of over 76,000 women treated with contemporary photon-based breast radiation, there was no significant difference in long-term cardiovascular events or mortality between left- and right-sided treatments suggesting modern radiation has largely mitigated prior cardiovascular risks. Small increases in certain outcomes (e.g., heart failure and ischemic heart disease) were observed in select subgroups, such as women younger than 50 and/or those receiving chemotherapy. An accompanying editorial puts it best: These patterns reinforce a multiple-hit model in which modest radiotherapy-related injury becomes clinically meaningful when layered on systemic therapy effects and a longer survivorship horizon” … implying “meticulous heart-sparing and aggressive cardiovascular risk prevention are likely to yield the greatest marginal benefit where baseline lifetime risk is highest.” | Nakajima, JAMA Netw Open 2026 & Guha, JAMA Netw Open 2026
