To chemo break or not to break? - Need second opinion!

After 2 yrs w/NED, my wife recently decided to drop Navelbine and continue
with Herceptin only. This was done even if her onc expressed some
reservations, but my wife felt she needed a chemo break. A brief history
below:

- first diagnosed HER2+++, w/mets to liver, in June 2000;
- Herceptin+Navelbine lead to NED by late 2000, Navelbine discontinued in
spring 2001, Herceptin discontinued in August 2001;
- NED lasts until March 2003 when diagnosed w/single brain lesion, which is
removed by craniotomy;
- successful gamma knife in June 2003 to clean new tumor growth around the
margin of the brain tumor area;
- PET scan reveals systemic disease is back in one lymph node in Oct 2003,
she is put back on Herceptin+Navelbine;
- NED again by Jan 2004;
- brain MRIs every 3 mos and PET scans every 6 mos have shown she's
remained NED for the past 2 yrs.

Her onc says that for (breast) cancer patients with past recurrences, going
"on" and "off" chemo is not necessarily advisable, as that can actually
cause resistance to the successful chemo treatment (and lower response) if
it needs to be started again. He prefers that Herceptin be accompanied by
chemotherapy in this case, presumably for an indefinite period of time, as
the results have been so good and she is having only minor side-effects.

We would welcome any reflections and/or personal experiences that anyone
might have on the kind of a bind that she finds herself in. The fact
remains that oncology is not an exact science and either option carries its
own risks, including remaining too long on chemo and building resistance.

Jay