A landmark study from the Spanish National Center for Cardiovascular Research elucidated immune system alterations that predict cardiotoxic events in cancer patients treated with immune checkpoint inhibitors (ICIs). Analysis of 215 patients showed shifts in immune populations correlating with heightened myocarditis risk, underscoring the need for early identification and monitoring strategies. This research offers a new avenue for mitigating life-threatening cardiac side effects associated with ICI therapies, advancing personalized safety management in oncology.