Once your healthcare provider knows you have breast cancer, the next step is to find out more about your specific cancer cells. This includes the stage of the cancer, as well as other factors. This information is learned from tests done on cancer cells that were taken out of your body in a procedure called a biopsy.
We’ve learned a lot about the biology of breast cancer: gene changes and other details that make breast cancer cells different from normal cells. In the past, breast cancer was staged based mostly on tumor size and spread (the TNM system). Today we use prognostic stage groups that also look at breast cancer cell biomarkers. In fact, these may be even more important than tumor size when looking at each woman’s likely outcome, the best medicines/chemo to use, and the value of local (tumor-focused) treatments like radiation.
While this detailed information allows doctors to use more personalized or focused treatment that’s designed for each woman based on the changes seen in her cancer cells, it also makes breast cancer staging very complex.
Here you will find more on the many different factors that are used to find each woman’s breast cancer prognostic stage group. Knowing these details can help you better understand your diagnosis and help you make treatment decisions that are best for you.
Stage is a way to note the size of the tumor and how far the cancer has spread in your body. Your healthcare provider uses exams and tests to find out the size of the cancer and where it is. He or she can also see if the cancer has grown into nearby areas, and if it has spread to other parts of your body.
The most commonly used system to stage breast cancer is the TNM system from the American Joint Committee on Cancer. Here's what the letters stand for in the TNM system:
T tells how far the main tumor has spread into nearby tissue.
N tells if the lymph nodes in the area of the original tumor have cancer in them. Lymph nodes are part of the immune system. They help the body fight infections.
M tells if the cancer has spread (metastasized) to distant organs in the body, such as the liver, lung, bone, or brain.
Numbers or letters after T, N, and M provide more details about each of these factors. There are also 2 other values that can be assigned:
X means the provider does not have enough information to assess the extent of the main tumor (TX), or if the lymph nodes have cancer cells in them (NX).
0 means no sign of cancer, such as no sign of spread to the lymph nodes (N0).
Your doctor may call this the cancer’s anatomic stage because it’s based on the anatomy or structure of the cancer. TNM staging helps to decide the type of surgery, if surgery to remove lymph nodes is needed, and if more treatment is needed after surgery.
The grade refers to how the cancer cells look when compared to normal breast cells. The grade of your cancer will help your doctor predict how fast the cancer may grow and spread.
A scale of 1 to 3 is used to grade breast cancer. The lower the number, the more the cancer cells look like normal cells. This means the cancer is less likely to spread and may be easier to treat and cure. Grade 3 cancer cells look very different from normal cells. This grade of cancer is more likely to grow quickly and spread.
Grade is written as G1, G2, and G3. Sometimes GX is used if the grade isn’t known.
HER2 stands for human epidermal growth factor receptor-2. Breast cancer cells that have a lot of this protein are called HER2-positive. (Results are either positive or negative.) They tend to grow faster and are more likely to spread to other parts of the body.
There are medicines that target and block HER2 to slow or stop cancer cell growth. If a woman’s breast cancer is HER2-positive, she should be treated with one of these medicines to get the best possible treatment outcomes.
Some breast cancer cells have hormone receptors. When the female hormones estrogen (ER) or progesterone (PR) attach to these receptors, they help the cells grow more quickly.
Tests can be done to see if a woman’s cancer cells have high amounts of hormone-receptors. The results will be ER-positive or negative (ER+ or ER+) and PR-positive or negative (PR+ or PR-).
This information is used to predict the cancer cell response to medicines that target these receptors. Medicines that block these receptors can slow or stop the growth of these cells. These medicines don’t work on breast cancer cells that are ER- and PR-negative.
All of the above information is put together into what’s called the prognostic stage group. These groupings give an overall description of your cancer.
A prognostic stage group can have a value of 0 to 4, and they're written as Roman numerals 0, I, II, II, and IV. The higher the number, the bigger the cancer is and/or the more it has spread beyond the breast. Letters are used after the Roman numeral to give more details.
All the details used in prognostic stage grouping help doctors choose the best treatments for each woman’s cancer and, as a result, get better treatment outcomes. These details also keep women from getting treatments that aren’t needed or won’t work.
Ki-67 is widely used as a marker of cancer cell proliferation–how fast the cancer cells are dividing. High Ki-67 levels mean that the cancer cells are dividing fast and certain chemo medicines (called anthracyclines) will work well to kill them. There’s no agreed standard use for this test at this time.But it can help guide treatment decisions and may also help predict overall outcomes.
Tests that look at patterns of many different gene changes at one time are becoming another important part of managing some early stage breast cancers (stages 0, I, and II). They’re useful because it’s not always clear that chemo is needed after surgery for these cancers.
These tests are often called multigene assays or gene expression assays. They look at changes in certain genes in breast cancer cells. The results can be used to help predict likely outcomes after treatment and the need for more treatment after surgery. The main thing the tests used today show is a woman’s risk of cancer coming back after treatment.
For instance, the test may give a recurrence score. This is a measure of the woman’s risk of the cancer coming back in the next 10 years. Other tests may give a risk assessment of how likely it is that the cancer will come back in another part of her body.
These test results can be very helpful when deciding if more treatment is needed after surgery. If the risk of recurrence is low, chemo is probably not needed. But if the risk is high, chemo could help keep the cancer from coming back.
Breast cancer staging is very complex. Remember the key information that’s needed includes:
The TNM values
Once your cancer is staged, your healthcare provider will talk with you about what the stage means for your treatment. Be sure to ask your healthcare provider to explain the stage of your cancer to you in a way you can understand. Make sure to ask any questions or talk about your concerns.