The Vanguard Study is a feasibility study to explore several aspects of evaluating multi-cancer detection (MCD) tests in a future definitive randomized controlled trial. An MCD test measures markers in the blood in order to screen for multiple cancers simultaneously. There is a need to understand how MCDs may work as cancer screening tools. The goal of cancer screening is to reduce the burden of cancer by identifying cancers before they show symptoms or signs, when treatment is likely to be most effective. In this study, adults aged 45-75 without cancer will be randomly assigned to one of 3 groups: 2 separate MCD test groups or a control group. These two MCD tests will not be compared to each other but will be compared to cancers detected in the control group. This study will provide early information on how well MCD tests perform as cancer screening tools. It will also help researchers understand how patients and their doctors make decisions about their care when the MCD test result comes back as normal (negative) or abnormal (positive).