How Treatment is Affected by Breast Cancer Type
In addition to how far your breast cancer has spread, your specific breast cancer type (the biology of the tumor) greatly influences the personalization of your breast cancer treatment. Typically, this is because at the molecular (cell) level, breast cancers differ in many ways. Looking at the genetic makeup of a tumor and profiling it based on its specific genes, also called a prognostic profile, can help doctors provide treatment that will give the most benefit to each patient individually.
Knowing which hormones, if any, are involved in the growth of the breast cancer, is critical information your oncologist needs in order to provide you with the best treatment. To get that information, they will run some tests that indicate the hormone receptor status and HER2/neu status of the breast cancer tumor. The results then play a large role in the type of breast cancer treatment that’s recommended. Four common results these tests produce include:
- Estrogen-receptor positive or negative (ER+/-), which means the breast cancer cells may or may not have receptors for the hormone, estrogen. ER+ results suggest that the cancer cells may receive signals from estrogen that could promote their growth.
- Progesterone-receptor positive or negative (PR+/-), which means the breast cancer cells may or may not have receptors for the hormone, progesterone. PR+ results mean that the cancer cells may receive signals from progesterone that could promote their growth.
- HER2 positive or negative, which means HER2 (human epidermal growth factor receptor 2)— a protein that appears on the surface of some breast cancer cells and plays a role in how a healthy breast cell grows— divides, and repairs itself. The presence, or lack thereof, will affect the treatment that’s chosen.
- Triple-negative breast cancer, which means the breast cancer cells test negative for estrogen receptors, progesterone receptors, and HER2. Triple-negative breast cancer will be treated differently than the other types of breast cancer since hormones are not playing a role in the breast cancer’s growth.
Hormone Status & Breast Cancer
Because of hormone receptors— special proteins inside the tumor cells, some breast cancer cells are fueled by estrogen and some by progesterone (the naturally occurring hormones in the female body). When hormones attach to hormone receptors, the cancer cells grow.
A hormone receptor status is either hormone receptor (HR) positive or hormone receptor (HR) negative.
- Hormone receptor-positive breast cancer cells have either estrogen (ER) or progesterone (PR) receptors. These breast cancers can be treated with hormone therapy drugs that lower estrogen levels or block estrogen receptors. HR-positive cancers are generally more common in women after menopause and tend to grow more slowly than those that are HR-negative.
- Hormone receptor-negative breast cancers do not have estrogen or progesterone receptors. This means that hormone therapy drugs will not be beneficial. HR-negative cancers are more common in women who have not yet gone through menopause and typically grow faster than HR-positive cancers.
Breast Cancer HER2 Status
Other factors that can influence how breast cancer behaves and also how it may respond to a specific cancer treatment are certain genes and the proteins they make. One such gene that can play a role in the development of breast cancer is HER2.
What it means to be HER2- negative or positive
- HER2-negative breast cancers do not have excess HER2. These tumors will not respond to therapies that specifically target HER2 receptors.
- HER2-positive breast cancers, on the other hand, have too much HER2 protein or extra copies of the HER2 gene. HER2-positive breast cancer treatment typically includes targeted therapy drugs that slow the growth and kill these cancer cells. These breast cancers are often fast-growing.
Information about HER2 status and whether or not it is playing a role in your cancer will typically be included in your pathology report. This will help your doctor select a medication that addresses HER2 positive patients.