How long on Herceptine if you have secondaries?

[DebsP]

Hello

I wonder if anyone can help me - I have mets to my liver and am currently on herceptine (since Jan this year). I know eventually the tumors will get immune to the drug - but just wondered the longest that someone with secondaries has stayed immune with the help of herceptin. I know everyone is unique and it depends on the mets, person etc - but as I say I just wondered. My onc says he has a lady that has been on it for 18 months.

Thank you for your help

Debs