Well, let's see -- guests are supposed to respond to any invitation, whether or not it says "RSVP," unless I guess it says "regrets only" and they are attending. So whiting out the RSVP line won't really change anything (and it will be a pain and look icky; I wouldn't do it).

But I suppose if you want, you could just cross it out with a pen stroke or add the words "not necessary."

Don't be so sure you don't want people to respond, though, even though you won't change your food plans. There might be other reasons you'd like to know if this one or that one is coming or not.

I wouldn't white out anything on a pre-printed invitation. It will ruin the look of your invitation as it infers there was a mistake that needed to be erased. Perhaps you could write the words "Regrets Only" w/your phone number in the spot for the response date.