Prospective, monocentric clinical study. Patients selected for nivolumab therapy in AP-HM for melanoma and non-small cell lung cancer will be eligible. Do not include patients with conditions that do not allow MRI, prior cardiovascular disease with LVEF<50%, cardiomyopathy, history of cardiac arrhythmia, history of cardiovascular toxicity under anticancer therapy, coronary artery disease or stroke less than 3 months Therapeutic management will not be modified and treatment will be administrated as usual.