Uneven tire wear

we have a 2005 toyota siena minivan all wheel drive It has run flat tires. The rear tires are wearing on the out side. 1.Can this be corrected with an alingnment 2. I have been told that all four tires mst be replaced or can Ireplace just the rears.

How many miles on the tires? Yes, it should be correctable with alignment, and yes, with AWD you probably have to replace them all. What does your owner’s manual say?