Can we use "RSVP" interchangeably with "RRSP"?

I received an email with the "RRSP" abbreviation.

"RRSP by 1 Nov 2011 to Willy Milly."

Upon checking with Thesaurus.com, it is a synonym of "RSVP".

Can one use "RRSP" and "RSVP" interchangeably?

RSVP means répondez, s’il vous plaît – “please reply.”

While Thesaurus.com lists RRSP as a synonym of RSVP, the link for RRSP takes you right back to RSVP.

This person faced the same dilemma of seeing RRSP on an invitation:

At the bottom of the invitation, it says “RRSP” – which is, obviously, the acronym for “Registered Retirement Savings Plan”.

So now I simply don’t know what to do. Should I reply to these people to tell them that we would love to come to their party, or should I simply donate some money to their RRSP?

The bottom line: RRSP is not a synonym of RSVP. Use RSVP when you mean RSVP.