Hi! Estrogen sensitive breast cancer is one of the absolute no no's for hcg. I also would not risk using the hhcg either, and heres why......there is alot that's unknown about how homeopathics work with your body...if they can mimic the effects of rx hcg for weight loss, I would be worried they could mimic also in terms of stimulating new tumor growth.....you really don't know for sure. Its better to be safe than sorry, I always say. . Sorry!