I beg to differ. Herceptin can cause heart problems. I had to take a three month "vacation" when my MUGA rating dropped considerably. After the "vacation," my MUGA returned to normal and I was put back on the Herceptin.
FDA Tells Doctors About Potential Heart Problems with Herceptin
As to the original question...your oncologist should be doing blood tests every few weeks (while on treatments - every few months or yearly thereafter) that include tumor markers (not extremely reliable, but they can show a pattern). Most people are considered NED (No Evidence of Disease) after getting clean margins with surgery. As there is no cure to cancer (YET), besides living life to the fullest you should pay attention to your body and be vigilant when you experience something different (persistent headaches, changes in vision...). My reoccurrence started as a persistent cough that was thought to be bronchitis or pneumonia. It was actually the BC in my lungs...I personally wish I had gotten yearly CAT scans, but most doctors won't order them unless you have a complaint. I now get PET, CAT and bone scans every three months, but I am at a high risk...many insurance companies wont pay for it otherwise. Talk to your oncologist and ask him/her what the plans are for future follow-up care....