Why Fec and Fec-T???

I was grade 3 her 2 pos cancer of unknown primary presumed breast and i was given 4 fec t and 4 tax before surgery, surgery to remove lymph nodes and 4 weeks of radiotherapy. 12 month of Herceptin. I have been told that they were throwing everything at me because they didnt know where the primary was for sure and in case it was lurking somewhere they wanted to be sure to get it. I am having my last herceptin Jan 11th and have been in remission for10 months now. I was lucky as i had an immediate response to the chemo.