What's my best plan of action?

The rails, I guess you'd call it, inside the rear passenger doors has started to rust through on just the tops of both sides. [passenger side a bit worse than the drivers side]
What are my options to fix this? What are the positives/negatives of each, and costs involved?

Thanks!

Anyone?

The rails? Do you mean the drip rails on the side of the car?

I guess that's what they are. it's the sill under the doors. The back ends of it where rear doors are.