Robyn,
Welcome to the site

Most of us who frequent the board are a little reluctant to give "treatment advice" per say, but I'm happy to share my treatment regimen with you regarding mets to scar area similar to what you describe, except, I had at least three that we knew of. BUT, I also had a skim met over the collarbone which was removed and tested positive, and suspicious axilla lymph nodes which weren't tested (these popped up during the 2 week interval after biopsy, before I started treatment.
Obviously, we knew we were dealing with an agressive and fast-moving recurrence, so we attacked with weekly Navelbine/Herceptin. Within a few weeks, the scar mets had "melted" away, and within a few months I was clinically NED, although I had altogether 6 months of this combo and then scans to confirm NED. This agressive regimen translated into 2 and 1/2 years of NED, being maintained on Herceptin alone, which was very easy for me to tolerate. I felt the discomfort(really) of being on chemo again was well worth it.
I also know that there are some who have posted here who have had good response to Hercptin alone.
Keep in mind that it is indeed your decision regarding QOL, but listed to your oncologist's advice and ask lots of questions.
Also, chemo regimens for some types of mets can be much easier to tolerate than treatment for primary disease, which is basically a scorched earth type of approach.
Good luck with your decision, keep us posted.
<3 Lolly