For patients with cancer and heart failure with reduced ejection fraction (HFrEF), ACEI is the most common renin-angiotensin-aldosterone system (RAAS) inhibitor prescribed by the respondents, followed by angiotensin receptor-neprilysin inhibitor (ARNI) (17.1%) and ARB (16.4%) (Supplementary Table 2). This evidence concerns the gene REN and heart failure.