A ring drawn from the Central West End buys clicks in two states
Radius targeting is a circle, and nothing about this metro is circular.
Draw a ring around a Central West End address and it will cover the city, a slice of St. Louis County, and a stretch of the Illinois side across the river. Draw one around a Chesterfield address and a good part of it lands in St. Charles County or in farmland. Neither circle matches the map of people who will actually drive to you.
Build geography from a list instead. Municipalities, ZIP codes, and where they exist, drive time polygons. The county is a patchwork of small separate cities, so a targeting list here is longer than in most metros. Fifteen named places beats one radius every time.
Then treat the city, the county and the Metro East as separate lines in the account rather than one blended blob. They convert differently, they cost differently, and blending them hides both facts.
The test for whether the geography is right: could your office manager read the list out loud and agree that a patient from each of those places would realistically show up on a Tuesday at four?