My doctor says it is a wait and see game after my Herceptin therapy. That if it is going to spread there's no way to know in advance and no way to test. He says I will have "symptoms" if it were to met's to my other organs. Hmmm...I had no "symptom whatsoever that I have breast cancer so what is he saying?
Essentially, he's saying that one of the hardest things about having cancer is the time after treatment is over because the fear that it will come back is still going to be there. Her2pos breast cancers are more likely to recur, but that's a statistic that can't predict what will happen to you. People at low risk for recurrence can recur, and people at higher risk of recurrence often stay well. Most doctors will follow up with regular blood work and physical exams that can help find a metastasis even if you aren't feeling any symptoms. But studies show that the majority of metastases are discovered when the patient reports a pain or problem.
I had every "bad" prognostic factor, including being Her2pos in the days before Herceptin was routinely given. Yet, here I am almost eleven years later, no recurrence, no metastases. I've wasted a lot of time worrying about something that hasn't happened. If my cancer had spread, the worry wouldn't have done a thing to help. I really do understand that advice about not worrying is easier to give than follow, but you'll find your balance between worrying yourself sick and being alert to possible symptoms as you go along.
If you look up DFS (disease-free survival rates) for those who have had Herceptin, the figures are very encouraging. They can be as high as 93% for those who have had AC-->TH chemo. I think doctors have to be very careful what they say, particularly in the litigious US, because if they tell you it won't come back and it does, you might sue them!
I think a BIG hurdle for women to get over is the point where your treatment is finished and you have to deal with the worry that the cancer might come back. You could try talking some common sense to yourself. Are you afraid to leave your house because you might get hit by a bus? You can use a mantra that will eventually overcome a tendency to live too much in fear - somehing like: "Yes, it is possible that my cancer might come back, but it most probably won't".
I'm preparing for this point in my life (still some months off, unfortunately) by visualising a box into which I'm putting all my cancer knowledge, thoughts and fears. After my last herceptin treatment, and I've had the all-clear, I'm going to mentally seal up the box and put it away. That way the cancer is a part of me and where I have been in my life, but it is stored away where I can forget about it unless or until I might need it again. My mental attic has a few such boxes and, like the storage areas of our house I forget what's there.
Good luck and best wishes.