ER-Positive Tumors and Hormone Therapy I recently learned that my cancer has metastasized to my bone. My oncologist put me on Femara, but my CA 27.29 numbers keep going up. My oncologist also said that if a person doesn't respond to one hormone therapy, they probably wouldn't respond to any others. Is that true? I'm not sure why your oncologist told you that if a person does not respond to one hormone therapy, they won't respond to another. Studies have found that one type of hormone treatment can be used after another has stopped working, and it is very common in breast cancer treatment to move a woman onto a new hormone treatment.
I would encourage you to get a second opinion from another oncologist. Since you have already taken tamoxifen, you would be a candidate for one of the aromatase inhibitors.
Once breast cancer has metastasized to the bone, letrozole (brand name Femara) is usually the first aromatase inhibitor that is tried. If your tumor does not respond to the Femara, then your oncologist will probably recommend that you try anastrozole (brand name Arimidex) or exemestane (brand name Aromasin). If these don't work, or if they stop working, your oncologist may recommend fulvestrant (brand name Faslodex). Faslodex is an estrogen receptor down-regulator. This means that Faslodex doesn't just stop estrogen from getting to the receptor, it changes the structure of the receptor itself. Without the estrogen receptor, the cancer cells can't get the estrogen they need to grow. It is given as a monthly injection, and it is only approved for use in postmenopausal women with hormone-positive metastatic breast cancer that has progressed following treatment with another hormonal treatment.
It can be worrisome when someone does not respond to hormone therapy, but then we move on and try another one. There are also many drugs that we used before this recent crop which also work quite well, such as diethylstilbestrol (DES, a synthetic estrogen) and megestrol (brand name Megace, a synthetic progesterone). Not all women will respond the same way to each drug, which is why you may need to try more than one before you find the one that will work for you. And since the key seems to be changing the hormonal milieu, sometimes just stopping a hormone therapy can give a response as well.
