Years ago, people viewed breast cancer as a single, monolithic, often fatal disease. The disease has been subdivided into four stages: Stage I, the tumor is small and has not spread beyond the site of origin; with stage II and III cancers, the tumor is larger than stage I and may have spread to the lymph nodes; and in stage IV, the cancer has spread or metastasized to other parts of the body.
Apart from their stages, these cancers were considered the same disease and each patient received the same treatment.
“But the scene is really only the amount cancer,” says Dr. Winer. And while stage is always part of determining treatment, it’s more important to consider the type cancer, he adds.
For this purpose, the types of breast cancers are classified according to their hormone receptors (estrogen and progesterone) and what is called “HER2” status.
Breast cancer cells that contain receptors for hormones such as estrogen and/or progesterone (which can help cancer cells grow) are said to be hormone receptor (HR) positive. And cancer cells that have high levels of the receptors are called human epidermal growth factor receptor 2 (HER2) positive. (HER2 is a protein that helps HER2-positive cancer cells grow.)
Cancer cells that do not contain hormones or HER2 receptors are called hormone receptor (HR) negative or HER2 negative, respectively.
And breast cancers that don’t have receptors for estrogen, progesterone, and HER2 are called triple negatives.
With this in mind, physicians now know that identifying the correct subtype of breast cancer helps to personalize treatment for that specific cancer, meaning a one-size-fits-all approach no longer applies.
“Even the smallest breast cancers, depending on their biology or type, may require targeted therapies that can help reduce the risk of recurrence,” says Dr. Lustberg. “Thanks to advances in clinical trials, breast cancer specialists are now better able to select beneficial therapies for different breast cancer subtypes, leading to better individual and overall outcomes.”