I have HER2 positive breast cancer and was told by my oncologist that herceptin was the one thing to give me the most protection to prevent it coming back elswhere in my body as this is an aggressive and fast growing cancer, it gives 80% more protection than chemo but you have to have chemo to get herceptin. The side effects are scary but they do keep a close eye on you, I was due for my 2nd injection last week but my echocardiogram came back too low and they stopped it, they have now s3nt me for a 2nd echocardiogram which was slightly higher so when I see my oncologist Friday I am hoping I can go back on it, it's like my safety blanket, if they do I will probably have to have an echocardiogram every couple of weeks instead of months as it does effect the heart walls, but it is reversible and it's  just a case of waiting till your heart builds up again. Hope this helps

Good luck

Krissy