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What’s the difference? Grading and staging allow oncologists to home in on a cancer’s characteristics

Cancer grading and staging
Cancer staging and grading provide much of that critical data to cancer care teams as they develop a patient’s treatment plan.

When a patient is diagnosed with cancer—any cancer—it’s important for doctors to get as much information about that specific tumor as possible. That information, in turn, is used to develop treatment options designed to attack the unique characteristics of a patient’s cancer.

Cancer staging and grading provide much of that critical data to cancer care teams as they develop a patient’s treatment plan. Staging may also be a factor in determining a patient’s prognosis, says Ajaz Khan, MD, Enterprise Chair of Medical Oncology at Cancer Treatment Centers of America® (CTCA). In general, he says, cancers diagnosed in stages 0 to 2 tend to have better long-term outcomes than cancers diagnosed in stages 3 or 4.

But the numerical ratings may be confusing to patients. Some may understand that a stage 1 diagnosis may result in a better treatment outcome than a stage 4 diagnosis. You may even know that a stage 1 cancer is found relatively early, while stage 4 means the cancer has spread to other parts of the body. But there’s so much more that goes into determining a specific cancer’s growth and the behavior of the cells that drive it.

In this article, we’ll explore:

If you’ve been diagnosed with cancer and are interested in a second opinion about your diagnosis or treatment plan, call us or chat online with a member of our team.

Staging vs. grading

Staging and grading are two different ways of trying to assess cancer, although they often overlap in some ways. Health professionals may use different staging and grading systems, depending on the type of cancer being investigated. Typically, for cancers with solid tumors:

Staging cancer evaluates the size of a tumor, its location and how far or aggressively the cancer may have spread.

Grading cancer assesses the makeup of cancer cells, trying to determine how aggressive the cancer is.

Staging is often broken down into two types:

  • Clinical staging examines the cancer using blood tests, physical exams, imaging tests and/or a biopsy.
  • Pathological staging is performed during and following surgery and provides more information about the cancer’s size and spread. It’s sometimes called surgical staging.

What are the different stages and grades of cancer?

Cancer stages

How oncologists define a cancer stage varies, depending on the type of cancer involved and which factors they incorporate into the staging system. In general, the stages of solid tumors are:

Stage 0: The cancer is in-situ or found where it started and before it has spread anywhere.

Stage 1: The cancer usually hasn’t grown into nearby tissue and hasn’t spread to the lymph nodes or other parts of the body.

Stage 2: The tumor has grown and cancer cells may be found in nearby lymph nodes.

Stage 3: The cancer is larger or embedded more deeply into nearby tissue or may have formed multiple tumors. It may have spread to nearby lymph nodes.

Stage 4: The cancer has metastasized and spread to other organs or distant parts of the body.

However, the cancer’s stage may not always tell the whole story about the potential treatment outcome, Dr. Khan says.

“We’ll see a patient who has a cancer of the tonsil or a cancer of the larynx (voice box),” Dr. Khan says. “The majority of those patients have stage 3 or 4 cancer, which may involve the lymph nodes. The minute they hear state 3 or 4, they’re thinking, ‘That’s it. I’m not going to survive this.’ For many of those patients, there’s a greater likelihood they may have no evidence of disease after we finish treating them. Remember, the stage doesn’t always tell us that we can’t treat for positive outcome. Not all the stages are always the same. Not all the stages are always the same.”

Your cancer stage will always stay the same, even if the cancer shrinks or spreads during or after treatment. For instance, if you’re diagnosed with stage 1 breast cancer, but the tumor later grows and spreads, it’s not considered stage 3 or 4 breast cancer. To determine whether the cancer has responded to treatment, a new stage may later be assigned an “r” in front of it to show that it’s different from the original stage.

In determining the stage, oncologists will often use the TNM system, which attaches a numerical value to three different categories:

T refers to the tumor, how big it is and how deeply it’s spread into nearby tissue.

N measures whether the cancer has spread to nearby lymph nodes and how extensively.

M describes whether the cancer has metastasized to other organs or areas of the body.

In the TNM staging system, the numbers attached to the letters usually denote severity. An M0, for example, would mean the cancer hasn’t metastasized, while an M1 would indicate it has.

Giving cancer a grade

Unlike staging, a cancer grade is based on the makeup of the cancer cells themselves.

Pathologists examine the cells of a tumor to determine how much they look like healthy cells. They typically grade them on a range, from being well-differentiated, meaning their appearance is most similar to normal cells’, to undifferentiated, which means they don’t resemble normal cells at all. The more distinct a tumor cell is from a healthy one, the more aggressive the cancer is considered. The general grades include:

Grade 1: Tumor cells generally resemble healthy cells (well-differentiated).

Grade 2: Tumor cells are somewhat abnormal (moderately differentiated).

Grade 3: Tumor cells are very abnormal (poorly differentiated).

Grade 4: Tumor cells considered the most abnormal (undifferentiated).

Not all cancer cells in a single tumor always look the same. Some may be well differentiated, while others are undifferentiated. The cancer grade is based on the most abnormal cells found.

“We rely on an expert diagnosis from our pathologists, who tell us the grade of a patient’s cancer,” Dr. Khan says. “The grading is variable, depending upon the type of cancer. What we’re really looking at essentially is prognostically, does that portend a good or bad prognosis for my patient based on what that grade is?”

Different cancers, different methods

Not all cancers are alike when it comes to staging and grading.

Brain cancer, for instance, only uses a grading system, not a staging system. Staging wouldn’t provide useful information in brain cancer, because it’s rare for a primary tumor in the brain to spread outside of the brain or away from the central nervous system. The severity of the disease is noted by its grade. For example, a patient with severe grade 4 brain cancer known as glioblastoma may be only months to live, while survival estimates for patients with grade 1 cancer such as glioma are measured in years.

Blood cancers such as multiple myeloma are evaluated in the opposite fashion: Doctors determine a stage, not a grade. The staging is also different for blood cancers that the system used for solid tumors.

Some cancers have unique grading or staging systems, including:

Gleason score: This score assesses a grade based on how prostate cancer cells behave on a micro level. This score is combined with a separate cancer grade, which denotes how abnormal the cancer cells appear as a way to assess how likely the cancer is to grow and spread.

Rai staging: This system stages chronic lymphocytic leukemia (CLL) based on blood cell counts. Its three main factors assess:

  • The number of lymphocytes in the blood
  • Whether the lymph nodes, spleen or liver are enlarged
  • Whether any blood disorders have developed

How is information used?

The staging and grading information are tools doctors use not only to assess a patient, but to communicate information to the other members of a patient’s cancer care team, providing a base line on the patient’s condition, prognosis and treatment options.

“This allows us to have a more collaborative conversation about what the next steps are for the patient,” Dr. Khan says.

The dynamics of staging cancer

How doctors stage cancer is evolving because of successes in cancer research.

“If we had this conversation three years ago, our breast cancer staging system was so less adept at capturing a lot of the things we see prognostically,” Dr. Khan says. “Outside the grade and the cancer diagnosis, receptors like estrogen and progesterone were never captured in the staging system, but now they are captured. So, we know, even if the patient has a little bit larger tumor but they have an excellent prognosis based on their receptors, they’re going to do much better than patients who don’t have those receptors.”

Instead of determining breast cancer’s stage based solely on anatomical factors, doctors may also use the receptor information to either lower stage if the receptors indicate a good prognosis, or increase the stage if they indicate a poor prognosis.

New methods, in turn, are also affecting treatment.

“In lung cancer, for example, we’re testing the patients upfront to see whether they could be candidates for immunotherapy, to see whether they could be candidates for a targeted therapy pill—along with completing chemotherapy—if they have early-stage cancer,” Dr. Khan says. “That’s allowing us to impact survival, quality of life and personalize care so more patients are living with a disease that years ago they would not survive.”

If you’ve been diagnosed with cancer and are interested a second opinion from CTCA about your diagnosis or treatment plan, call us or chat online with a member of our team.