You might remember the factually misguided “death panel” attack on the Affordable Care Act, which preyed on discomfort with a governmental role in deciding what health care would or would not be paid for. (This discomfort also extends to private plans, exemplified by the backlash against managed care in the 1990s.)

Perhaps as a result, Americans don’t often talk about what treatments and services provide enough value to warrant coverage.

Two classes of Medicare

You can divide current Medicare coverage into two layers.

The first is relatively transparent. Traditional Medicare does not cover certain classes of care, including eyeglasses, hearing aids, dental or long-term care. When the classes of things it covers changes, or is under debate, there’s a big, bruising fight with a lot of public comment. The most recent battle added prescription drug coverage through legislation that passed in 2003.

Over the years, there have also been legislative efforts to add coverage for eyeglasses, hearing aids, dental and long-term care — none of them successful. Some of these are available through private plans. So a Medicare for all program that excluded all private insurance coverage and that resembled today’s traditional Medicare would leave Americans with significant coverage gaps. Most likely, debate over what Medicare for all would cover would center on this issue.

But there is a second layer of coverage that receives less attention. Which specific treatments does Medicare pay for within its classes of coverage? For instance, Medicare covers hospital and doctor visits associated with cancer care — but which specific cancer treatments?