Is Herceptin working and the need for scans

[Rolepaul]

8 mm, node negative, HER+. You are considered low risk for a recurrence! That being said, I do like the blood tests to track things. I think the tests are going to become more common in the near future. The push is to be able to test for issues, in the same manner as for high blood pressure and high lipids.
You caught it early. That likely saved you from future issues. Stay vigilant to changes in your body and mind, but it is unlikely that you will see the disease comeback.