tumors/herceptin

I'm curious to know how many are on Herceptin only and NOT NED. In other words, who still has tumors, but is not receiving chemo. My sister was wondering how long she would stay on chemo. Do you think she could stop chemo and take only Herceptin to keep the cancer from spreading more? At this point she's been on Taxol/Herceptin for almost 6 months. This combo has managed to stop the spread, though there is still much of her liver diseased, as well as bones, brain and spots on spleen and kidney (which may be gone by now.) Doctor want to switch her to Navelbine/Herceptin at the end of the month due to neuropathy. Any thoughts on this would be SO appreciated.