Docs positions will obviously vary in this territory, even more than they do with "established" regimens. Does Kattlove use any off label treatments? I think the adjuvant setting would have a different level of criteria than metastatic. Approved and commonly used drugs may be equally or more unpredictable, with far higher toxicity. Considering the info available at this point and the fact that many cancer patients already take it, I'm comfortable with mom having taken it for about a year at a low dose. This isn't fully up to date but provided background:
http://her2support.org/vbulletin/showthread.php?t=39740
Note that there seems to be more than insulin/sugar in play regarding benefit.