1996 Cadillac Deville Brake Pad

My right rear brake rotor has a peculiar wear pattern. The top of the rotor has a normal polished wear band from the pad, with another polished wear band at the bottom. Between them is a rust band indicating the center of the pad is not touching the rotor when the car is braked. It is almost as if the pad is warped in the middle and not contacting the rotor evenly across its surface.

Is this possible? What could the problem be? Does it require an entire brake job on the rear wheels?

I have never seen this in all my years working on cars.

Thanx.