Breast Cancer 101

Cancer is cancer, right?  The only difference is where it is found, right?  WRONG.  Each cancer is different, and each breast cancer is different.  Don't worry, I was clueless before I had to get educated ASAP.

Here are a few things I have learned about Breast Cancer, in laypersons terms.

Hormone Receptor Status - Hormone receptors are proteins on the breast/tumor that receive signals from the breast(or tumor) to grow.  The two hormones are Estrogen and Progesterone.  Commonly abbreviated as ER+ or ER- and PR+ or PR-.  The pathology report of the tumor, usually from a Biopsy or from surgery will indicate the hormone receptor status.  Basically it tells you if Estrogen or Progesterone "feeds" the cancer or not.

ER+ tumors - There are drugs, Tamoxifen or Aromatase Inhibitors that will block your natural estrogen production.  These are usually taken for 5 to 10 years (yeah, I said YEARS) after your treatment to prevent recurrence.  Tamoxifen has been around for years and was initially given for 10 years.  Further studies showed that 5 years was just as effective.  I believe there are current studies going on to see if 2 years are just as effective.  Aromatase Inhibitors are a similar type of drug as Tamoxifen but are given to postmenopausal women.  Tamoxifen is now just given to premenapausal women although prior to armotase inhibitors it was given to all women regardless of their menapausal state.

There are no known drugs to take to reduce the recurrence of ER- or PR+or- tumors.

The following is a breakdown of the frequency of the hormone receptor status of tumors, from breastcancer.org

• ER+: About 80% of breast cancers are estrogen-receptor positive.
• ER+/PR+: About 65% of estrogen-receptor-positive breast cancers are also progesterone-receptor-positive. This means that the cells have receptors for both hormones, which could be supporting the growth of the breast cancer.
• ER+/PR-: About 13% of breast cancers are estrogen-receptor-positive and progesterone-receptor-negative. This means that estrogen, but not progesterone, may be supporting the growth and spread of the cancer cells.
• ER-/PR+: About 2% of breast cancers are estrogen-receptor-negative and progesterone-receptor-positive. This means that the hormone progesterone is likely to support the growth of this cancer. Only a small number of breast cancers test negative for estrogen receptors but positive for progesterone receptors. More research is needed to better understand progesterone-receptor-positive breast cancers.
• ER-/PR-: If the breast cancer cells do not have receptors for either hormone, the cancer is considered estrogen-receptor-negative and progesterone-receptor-negative (or “hormone-receptor-negative”). About 25% of breast cancers fit into this category.

Human Epidermal growth factor Receptor 2 Status

This is a little more difficult to describe, but I will try anyway.  My understanding of HER2 is that it is a known "feeder" of breast cancer cells and that it tends to be more aggressive than HER2- breast cancer.  Prognosis used to be worse for the 25% of patients that had the HER 2 mutation.  Herceptin (Trastuzumab)
 a new drug that is helping save several lives.  It is referred to as a targeted therapy as it is a monoclonal antibody that is specifically targeted to the HER2 protein.

Here is an excerpt from breastcancer.org.  

The HER2 gene makes HER2 proteins. HER2 proteins are receptors on breast cells. Normally, HER2 receptors help control how a healthy breast cell grows, divides, and repairs itself. But in about 25% of breast cancers, the HER2 gene doesn't work correctly and makes too many copies of itself (known as HER2 gene amplification). All these extra HER2 genes tell breast cells to make too many HER2 receptors (HER2 protein overexpression). This makes breast cells grow and divide in an uncontrolled way.

Breast cancers with HER2 gene amplification or HER2 protein overexpression are called HER2-positive in the pathology report. HER2-positive breast cancers tend to grow faster and are more likely to spread and come back compared to HER2-negative breast cancers. But there are medicines specifically for HER2-positive breast cancers.

Summary
There are 3 main ways to classify a breast cancer tumor, ER status, PR Status and HER2 Status.  HER2 positive is generally aggressive, as are tumors that are negative for all, called triple negative.

Treatment is based on the ER, PR and HER2 status of your tumor.  ER+ can be given an estrogen blocking drug such as Tamoxifen or an Aromatase Inhibitor.  HER2+ can be given Herceptin, a recent targeted therapy.

Disclaimer - I am not a doctor so please consult your doctor.  I am just trying to explain my understanding of things in a clear and concise manner.