Unfortunately no, if you're pre menopausal you take tamoxifen (and be thankful there,is something you can take, as our triple negative sisters would jump at the chance to take something). If you're post menopausal you will go on an aromatase inhibitor.
I'm on tamoxifen, I hate it, but I'm sticking to it (need to take 2 extra meds to control the side effects). I didn't gain weight during chemo, but gained weight after starting the tamoxifen. I'm now on a diet.
A randomized trial showed there is no weight gain due to,tamoxifen. Then why so many of us patients complain about it? It has been suggested that we eat more and exercise less than we used to before BC, possibly because of fears with our operations, lack of energy, depression. I did find a scientific article that suggests tamoxifen has a negative impact on lean muscle mass.
I suggest you join the rest of us in calorie controlled healthy eating and exercise. Here's an article about myths that get in the way of weight loss, hope you find it helpful:
Just look at this as an opportunity to be healthy and continue fighting.