My ER and PR weren't quite as low as yours but everything else in my treatment was the same. My onc gave me Tamoxifen and said to try it which I did and had horrendous side effects, so I stopped. My surgeon however said that in his experience the Herceptin was more of a wonder drug along with the radiotherapy for preventing a recurrence than anything else.
I think what you need to ask yourself is would you feel better mentally if you took it or would be quite ok not taking it.
I was happy with my decision not to take it, I know it could come back, but then I am quite philosphical in that I could take Tamoxifen for 5 years, 10 years and then it could still come back.
Main thing you have to be happy in yourself with your decision.
Don't know if that is of any help to you, but hopefully it is.
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