Understanding Colorectal Cancer

Learn more about the importance of colorectal cancer screening and how colorectal cancer is diagnosed, staged, and treated so you can make informed decisions about your care.

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Colorectal Cancer Screening and Diagnosis

Symptoms of colorectal cancer are not always obvious until the disease has reached an advanced stage. This is why it is essential to discuss your family history with your doctor and determine the appropriate time to begin colorectal cancer screening.

Screening for colorectal cancer starts at age 45, among those who are at average risk. It should begin earlier for those at advanced risk of colorectal cancer.

For all individuals, the gold standard screening test is a colonoscopy. The colonoscopy involves a flexible lighted tube that examines the entire colon and rectum. It also allows for the removal of tissue samples if needed.

Other tests that are also used include stool-based testing or virtual colonoscopy.

Staging Colorectal Cancer

After a colorectal cancer diagnosis, your oncologist will determine the extent of your cancer. This process is known as staging, an essential part of treatment planning. Staging describes how far the cancer has advanced, including its location and whether it has spread (metastasized) beyond the colon or rectum.

The Stages of Colorectal Cancer

The TNM system, developed by the American Joint Committee on Cancer (AJCC), is the most widely used method for staging colorectal cancer. TNM stands for:

T: the size of the tumor and any spread of cancer into nearby tissue
N: the spread of cancer to nearby lymph nodes
M: metastasis, which refers to the spread of cancer to other parts of the body

Stages on a pathology report will be indicated by Roman numerals 0 through IV, with lower numbers indicating less cancer spread.

TNM staging for colorectal cancer is as follows:

Tumor (T)

TX: The primary tumor cannot be evaluated.
T0 (T zero): No evidence of cancer in the colon or rectum.
Tis: Refers to carcinoma in situ, where cancer cells are found only in the epithelium or lamina propria, the top layers lining the inside of the colon or rectum.
T1: The tumor has grown into the submucosa, the layer of tissue underneath the mucosa or lining of the colon.
T2: The tumor has grown into the muscularis propria, a deeper muscle layer that contracts to move contents through the intestines.
T3: The tumor has grown through the muscularis propria and into the subserosa or has grown into tissues surrounding the colon or rectum.
T4a: The tumor has grown into the surface of the visceral peritoneum, indicating it has grown through all layers of the colon.
T4b: The tumor has grown into or attached to other organs or structures.

Node (N)

NX: The regional lymph nodes cannot be evaluated.
N0 (N zero): No spread to regional lymph nodes.
N1a: Tumor cells found in 1 regional lymph node.
N1b: Tumor cells found in 2 or 3 regional lymph nodes.
N1c: Tumor nodules in nearby structures that do not appear to be lymph nodes.
N2a: Tumor cells found in 4 to 6 regional lymph nodes.
N2b: Tumor cells found in 7 or more regional lymph nodes.

Metastasis (M)

M0 (M zero): The disease has not spread to a distant part of the body.
M1a: Cancer has spread to 1 other part of the body beyond the colon or rectum.
M1b: Cancer has spread to more than 1 part of the body other than the colon or rectum.
M1c: Cancer has spread to the peritoneal surface.

Grade

The grade (G) of the tumor is another important factor used to determine the state of colorectal cancer. The grade describes how closely cancer cells resemble healthy cells when viewed under a microscope. When cancer cells look similar to normal cells, it is called "differentiated" or a "low-grade tumor." Cancer cells that look very different from normal cells are called “poorly differentiated” or “high-grade tumors.”

GX: The tumor grade cannot be determined.
G1: The cells closely resemble healthy cells and are called well differentiated.
G2: The cells somewhat resemble healthy cells and are called moderately differentiated.
G3: The cells look less like healthy cells and are called poorly differentiated.
G4: The cells barely resemble healthy cells and are called undifferentiated.

Doctors describe colorectal cancer by the following stages:

Stage 0 Colorectal Cancer

Also called carcinoma in situ, cancer is detected only in the innermost lining of the colon or rectum.

Stage I Colorectal Cancer

Cancer has grown into the inner wall of the colon or rectum but has not grown through the wall (T1 or T2, N0, M0).

Stage II Colorectal Cancer

Stage IIA: The cancer has grown through the wall of the colon or rectum but has not spread to nearby tissue or to the nearby lymph nodes (T3, N0, M0).
Stage IIB: The cancer has penetrated the layers of the muscle to the lining of the abdomen, but has not spread to the nearby lymph nodes or elsewhere (T4a, N0, M0).
Stage IIC: The tumor has grown through the wall of the colon or rectum and has invaded nearby structures. It has not spread to the nearby lymph nodes or elsewhere (T4b, N0, M0).

Stage III Colorectal Cancer

Stage IIIA: Cancer has grown through the inner lining or into the muscle layers of the intestine and has spread to 1 to 3 lymph nodes or to a nodule of tumor cells in tissues around the colon or rectum that do not appear to be lymph nodes. It has not spread to distant parts of the body (T1 or T2, N1 or N1c, M0; or T1, N2a, M0).
Stage IIIB: The cancer has grown through the bowel wall or to surrounding organs, affecting 1 to 3 lymph nodes or involving a tumor nodule around the colon or rectum that are not lymph nodes. It has not metastasized to other parts of the body (T3 or T4a, N1 or N1c, M0; T2 or T3, N2a, M0; or T1 or T2, N2b, M0).
Stage IIIC: Regardless of how deep it has grown, the cancer has spread to 4 or more lymph nodes but not to other distant parts of the body (T4a, N2a, M0; T3 or T4a, N2b, M0; or T4b, N1 or N2, M0).

Stage IV Colorectal Cancer

Stage IVA: The cancer has metastasized to a single distant part of the body, such as the liver or lungs (any T, any N, M1a).
Stage IVB: The cancer has spread to multiple distant sites (any T, any N, M1b).
Stage IVC: The cancer has spread to the peritoneum and may also have spread to other sites or organs (any T, any N, M1c).

Recurrent Colorectal Cancer

Recurrent colorectal cancer is cancer that returns after treatment, even after a time when it was not detectable. This occurs when cancer cells remain in the body, stay inactive for a period, and later begin to grow again in the colon, rectum, or other areas.

Find a Colorectal Cancer Specialist in the Syracuse Area

At Hematology-Oncology Associates of CNY, we are committed to providing expert, patient-centered colon and rectal cancer care. Our multidisciplinary team of specialists ensures that each patient receives a personalized treatment plan based on the latest advancements in colorectal cancer care.

Our cancer centers offer care for patients in Central New York, in the Syracuse area, including Camillus and all of Onondaga County; Auburn, and the rest of Cayuga County; Madison County, including Oneida; Oneida County, including Utica and Verona; Oswego County, including Oswego and Fulton; Watertown, and throughout Jefferson County.