Hi WTY
From what I've read and what my several oncos (I've gone for several 2nd opinions in the last few years
), HER2+ BC is mainly driven by HER2+ gene more than ER/PR+. That's why the addition of Herceptin is so important to arrest the HER2+ BC.
I was actually ER/PR+ (via biopsy) upon diagnosis of the liver met 4.5 year ago. My onco then immediately started me on Herceptin and Navelbine, no hormonal treatment. I'd a mastectomy after the chemo. That's when the pathology changed to ER/PR-. Her2+ status never changed.
That said, I can't conclude if Navelbine will be effective for you..hope you'll understand. Recent research has shown there is good synergistic effect between Herceptin and Navelbine. Another golden standard of care for HER2+ BC is actually Taxotere, Carboplatin and Herceptin. I'm on this combo now (Taxol instead of taxotere) and have seen regression in my liver met, which I'm very thankful for.
Hope this helps.