Is there a possibilty of cancer metastases while herceptin (trastuzumab) session is still on going ?

Theoretically, yes. : Herceptin (trastuzumab) is used to treat breast cancers that have her2/neu receptors. While this drug is very effective, it will not eradicate all breast cancer cells 100% of the time. Therefore, it is possible to be diagnosed with metastatic disease despite ongoing treatment (although we certainly hope not). Of course, every case is unique & the best dr. To talk to is the treating physician. Good luck!

Yes: To start with her 2 positive breast cancers are very aggressive tumors, due to over expression of her 2 gene ( makes her 2 protein causing uncontrollable growth ) Herceptin (trastuzumab) , a monoclonal antibody controls that growth , it is possible tumor can spread simultaneously during course of treatment.