Hormone therapy for breast cancer: built on success.
Most breast cancer cases can respond to hormone therapy, and this has been appreciated for more than a century, as illustrated by the timeline we put together for you in our feature article, "The Estrogen Effect."
This issue gives you a historic perspective and future snapshot of hormone therapy and how estrogen receptor pathways have been co-opted by cancer cells to sustain growth.
Just this year, we have seen a new drug approved for metastatic, hormone receptor-positive breast cancer patients. Afinitor (everolimus), an inhibitor of a growth signaling pathway regulator known as mTOR, has already been approved for other cancer types.
Afinitor reverses resistance to hormone therapy, enhancing the effect when the two are combined. This drug represents a big step, with a doubling of progression-free survival—one of the biggest improvements we have ever seen with the addition of one drug. The trial results are not mature enough yet to know whether overall survival is improved, but data are already trending in that direction. The treatment is not without side effects, and we will need to learn how to minimize these as our clinical experience grows.
This development continues to raise hopes that we can turn this form of breast cancer into a chronic disease, maybe to the point that most people will have a normal lifespan even with metastases. That idea may have been far-fetched not too long ago, but we now know more about hormonal pathways and how they vary from case to case.
Other drugs that target proteins such as PI3 kinase, Akt, insulin-like growth factor receptor, GRP78 endoplasmic stress response protein and myriad others are in various stages of development, specifically to prolong responses to hormone therapy. Those that work in the advanced setting will be tested in early-stage breast cancer along with hormone therapies to prevent metastases in the first place. Plans are already under way to test Afinitor in patients with early-stage, hormone receptor-positive breast cancer.
This issue gives you a historic perspective and future snapshot of hormone therapy and how estrogen receptor pathways have been co-opted by cancer cells to sustain growth. Currently, we can reverse some of these mechanisms, but by no means all of them, and not sufficiently enough to cure advanced breast cancer. But it is clear that we are on a pathway to increase longevity for patients with this type of cancer.
You can find more breast cancer updates from Dr. Tripathy in "Are New Therapies in ER-Positive Breast Cancer Just the Tip of the Iceberg?"