Our knowledge on cardiovascular side effects of immune checkpoint inhibitors (ICIs) is restricted to this date to observational retrospective data (mainly case series and pharamcovigilance analysis). We aim at assessing the incidence of cardiovascular adverse side effects of ICIs by means of a prospective interventional single centre study using multiple biomarkers.

Immune checkpoint inhibitors (ICIs) are drastically improving cancer prognosis. Cardiovascular adverse side effects of ICIs are though to be rare but may be responsible for ~50% death rates.

Prospective screening for cardiovascular and muscular immune related side effects has not been undertaken independently from the industry.

The aim is to describe the incidence of these side effects by means of serial assessment in patients undergoing ICI therapy for cancer. Biomarkers as ECG, echocardiography, cardiac magnetic resonance imaging and long-term ECG monitoring will be undertaken at inclusion (before ICI therapy is started), and during the first cycle treatments and at 6 months follow-up.

Mean endpoint encompasses cardiovascular and muscular adverse side effects between the 2nd and the 3rd ICI cycle. Secondary endpoints include cardiovascular and muscular adverse side effects at 6 months follow-up, and the incidence of individual side effects.

4 ancillary studies based on patients' blood biobanking are also planned. Their objectives are:

• to assess sensitivity of heart failure biomarkers in predicting cardiovascular events under ICI,
• to assess sensitivity of cytokine biomarkers in predicting cardiovascular events under ICI,
• to bank cells to induce cardiomyocytes from stem cells
• to bank DNA to identify genetic factors related to occurrence of cardiovascular events under ICI

Inclusion Criteria:

- prescribed treatment by immune checkpoint inhibitors (ICI) for cancer

Exclusion Criteria:

• previous treatment by any ICI
• any contraindication to cardiac resonance magnetic imaging
• contraindication to gadoteric acid, meglumin or any gadolinium-based contrast agent
• pace maker or automated implantable defibrilator
• pregnancy, breastfeeding
• women of childbearing potential who do not use one of the following methods of birth control: hormonal contraception or intrauterine device or bilateral tubal occlusion
• patient under legal protection
• renal failure defined by creatinine clearance <30ml/min/m² (CKD-EPI)
• current participation or exclusion period of another interventional clinical study

Exclusion Criteria for ancillary studies:

- hemoglobinemia < 9 g/dl

Patients undergoing ICI therapy for cancer before the start of treatment.

Individual participant data (IPD) that underlie results in publication could be shared. IPD detailed in the protocol of a planned metaanalysis could be shared

Two years after the last publication

Data sharing must be accepted by the sponsor and the PI based on a scientific project and scientific involvement of the PI team. Collaboration will be fostered.

Teams wishing obtain IPD must meet the sponsor and IP team to present scientific (and commercial) purpose, IPD needed, format of data transmission, and timeframe. Technical feasibility and financial support will be discussed before mandatory contractual agreement. Processing of shared data must comply with European General Data Protection Regulation (GDPR).