Rusty cast-iron sewer pipes - any options other than replace?

[Andrew S.]

I have a problem with a cast-iron sewer pipe in one of my rentals.  It clogs up frequently and according to the plumber who just snaked it, the issue is likely paper getting hung up on the rusty insides of the pipes.  We are talking basement apartment here and replacing the pipe will involve opening up the concrete floor (expensive, obviously), so before I bite the bullet, I wanted to see if someone knows of any alternative fixes.  Are there liners that one could install at least for a semi-permanent fix?  Has anyone had any luck with such products?

I know roto-rooter peddles an additive (60 bucks a gallon) that you are supposed to dump down the drain (just writing that makes me cringe...) that they claim will form some sort of a smooth film, but that sounds rather far-fetched to me - has any had luck with that?

Any suggestions appreciated!