What Do Stage and Grade Mean In Colorectal Cancer?

Colorectal cancer, which includes both colon cancer and rectal cancer, makes up about 8% of cancer cases in the U.S. If you or a loved one has been diagnosed with colorectal cancer, your first question is probably about treatment. But before healthcare providers can decide on the best treatment, they need to determine the cancer stage and the tumor grade. 

Let’s define these terms and discuss how stage and grade determine treatment and prognosis in people with colorectal cancer.

What’s the difference between stage and grade? 

Cancer staging describes the extent of a cancer within the body. For colorectal cancer, stage is determined using a system called the TNM classification. This system classifies cancers according to: 

• T classification: how deeply the tumor invades into the wall of the colon or rectum

• N classification: whether the cancer has spread to nearby lymph nodes

• M classification: whether the cancer has spread to other parts of the body

The TNM factors are combined to determine the cancer stage. In general, cancers that don’t extend outside of the colon or rectum are considered stage 1. If a tumor extends through the wall of the colon or rectum, it’s considered stage 2. Cancers that have spread to the lymph nodes are usually stage 3, and those that have spread to other areas of the body are considered stage 4.

Tumor grade describes what the cancer cells look like under a microscope. You can think of grade as describing how much the tumor cells resemble normal, noncancerous cells. Colorectal cancers are grade 1 (low grade), grade 2 (intermediate grade), or grade 3 (high grade). Low-grade tumor cells look more like normal tissues than high-grade tumors. The higher the grade, the more aggressive the cancer is likely to be.

How do colorectal cancer staging and grading affect treatment options?

Healthcare providers look at many factors to determine the best treatment for a person with colorectal cancer. Treatment options for colorectal cancer include:

• Surgery

• Radiation therapy

• Chemotherapy (such as FOLFOX or Xeloda)

• Targeted therapy

• Immunotherapy

Cancer stage is one of the most important factors used to determine treatment for a person with colorectal cancer. Although every case is different, here are some common colorectal cancer treatments, according to stage:

• Stage 1 colorectal cancer: surgery alone

• Stage 2 colorectal cancer: surgery, then chemotherapy (in some cases)

• Stage 3 colon cancer: surgery, then chemotherapy

• Stage 3 rectal cancer: chemotherapy and radiation therapy, then surgery

• Stage 4 colorectal cancer: chemotherapy, and/or targeted therapy, and/or immunotherapy

Tumor grade may be used along with cancer stage to help healthcare providers make treatment decisions. However, stage is usually considered to be the more important factor.

How do colorectal cancer staging and grading affect prognosis?

Cancer stage is one of the most important predictors of outcome for a person with colorectal cancer. Stages 1 to 3 colorectal cancers are considered curable. In fact, the 5-year survival for stages 1 to 2 colorectal cancer is about 90%. Stage 4 colorectal cancers, on the other hand, are not considered curable and have a worse prognosis.

For all stages of colorectal cancer, higher-grade tumors behave more aggressively. This means that, compared to low-grade tumors, they’re more likely to spread to other parts of the body and come back after treatment.

How are colorectal cancer stage and grade determined?

To determine the stage of a colorectal cancer, healthcare providers rely on:

• Physical examination

• Imaging tests (MRI, CT, ultrasound, PET)

• Surgical pathology findings, including:

• • Tumor size

  • How deeply the tumor invades into the wall of the colon or rectum

  • Whether the tumor invades into nearby organs, like the bladder, vagina, or prostate gland

  • Whether the tumor involves lymph nodes

Tumor grade is determined by the microscopic appearance of the cancer cells. After a biopsy or surgical removal of a tumor, a pathologist will look at the cancer cells under a microscope and assign the grade.

How quickly can a cancer’s stage or grade change?

Cancer stage is usually assigned at the time of cancer diagnosis, after the biopsy and imaging tests have been completed. But the cancer stage can change if new information becomes available. For example, if a new imaging test (like a CT scan or an MRI) shows cancer in a place where it hadn’t been seen before, the cancer stage may be adjusted.

Cancer grade is evaluated whenever new tissue is being studied, either from a biopsy or from a surgery. In some cases, the tumor grade will change between the biopsy and surgery. This difference doesn’t necessarily mean that the tumor has changed. It might just reflect differences between the parts of the tumor that were tested during the biopsy and the surgery.

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Written by:

David Marcus, MD

David Marcus, MD, is a board-certified radiation oncologist with expertise in the management of many types of cancer, including prostate cancer, breast cancer, and several others. He earned his medical degree at Emory University in Atlanta, Georgia, where he also completed residency training in radiation oncology.

Edited by:

Mandy Armitage, MD

Mandy Armitage, MD, has combined her interests in clinical medicine with her passion for education and content development for many years. She served as medical director for the health technology companies HealthLoop (now Get Well) and Doximity.

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