ACS :: How Is Anal Cancer Staged?

Staging is the process of finding out how far a cancer has spread. This is important because treatment options and outlook for recovery and survival depend on the cancer's stage. If you have anal cancer, ask your cancer care team to explain the staging in a way that you understand. Knowing all you can about staging lets you take a more active role in making informed decisions about your treatment.

The tests described above (in the section, "How is anal cancer diagnosed?") are the ones used to determine the stage of the cancer.

Staging of anal cancer uses a system created by the American Joint Committee on Cancer (AJCC). The staging description that follows applies only to tumors in the anal canal, not to cancers that involve only the anal margin or perianal skin.

Numbers or letters appear after T, N, and M to provide more details about each of these factors:

TX: Primary tumor cannot be assessed
T0: No evidence of primary tumor
Tis: Carcinoma in situ
T1: The tumor is 2 cm (about 4/5 inch) across or smaller
T2: Tumor is between 2 and 5 cm in size (about 1 to 2 inches).
T3: Tumor is larger than 5 cm.
T4: Tumor of any size that is growing into nearby organ(s), such as the vagina, urethra (the tube that carries urine out of the bladder), prostate gland, or bladder

NX: Regional lymph nodes cannot be assessed
N0: No regional lymph node spread
N1: Spread to lymph nodes near the rectum
N2: Spread to lymph nodes on one side of the groin and/or pelvis
N3: Spread to lymph nodes near the rectum and in the pelvis or groin, or to both sides of the groin or pelvis

MX: Presence of distant metastasis cannot be assessed
M0: No distant spread
M1: Distant spread to internal organs or lymph nodes of the abdomen

To make this information more helpful, these TNM descriptions can be grouped together into a simpler set of stages, labeled stage 0 through stage IV.

Stage 0: Tis, N0, M0: Stage 0 is very early cancer (or precancer) that exists only in the top layer of anal tissue. This stage is also known as carcinoma in situ.

Stage I: T1, N0, M0: The cancer cells have spread beyond the top layer of anal tissue and is no longer carcinoma in situ. The tumor is less than 2 cm (about 4/5 inch) in size. It has not spread to lymph nodes or distant sites.

Stage II: T2 or 3, N0, M0: The cancer is larger than 2 cm in size, but it has not spread to nearby organs or lymph nodes. It has not spread to distant sites.

Stage IIIA: (T1-3, N1, M0) or (T4, N0, M0): The cancer can be any size and either has spread to the lymph nodes around the rectum(N1), or it has grown into nearby organs (T4), such as the vagina or the bladder without spreading to nearby lymph nodes. It has not spread to distant sites.

Stage IIIB: (T4, N1, M0), or (Any T, N2-3, M0): Either the cancer has grown into nearby organs, such as the vagina or the bladder, and has also spread to lymph nodes around the rectum, or it can be of any size but has spread to lymph nodes in the groin, with or without spread to lymph nodes around the rectum. It has not spread to distant sites.

Stage IV: Any T, Any N, M1: The cancer has spread to distant organs or tissues. It can be any size and may or may not have spread to lymph nodes.

Recurrent: Cancer that comes back after treatment is called recurrent. If the cancer comes back in or near the place it started it is called a local recurrence. If the cancer comes back in another part of the body, it is called a distant recurrence.

Because anal cancer is uncommon, statistics on survival are not exact. They depend on reporting from centers that only see a small number of patients.

The highest number of patients is collected by the SEER database of the National Cancer Institute. The SEER does not report survival of patients with anal cancers by TNM stage. Instead it divides them into 3 groups: localized (corresponds roughly to stages I and II), regional (corresponds roughly to stage IIIA), and distant (corresponds roughly to stages IIIB and IV).

The 5-year survival rate is a standard way to report the survival of people with cancer. This rate is the percent of patients who live at least 5 years after their cancer is diagnosed. Many of these patients may live much longer than 5 years after diagnosis, but 5-year rates are often used to look at outcomes. Relative survival rates assume that people with anal cancer will die of other causes and compare the observed survival with that expected for people without anal cancer. That means that relative survival only reflects deaths from anal cancer. This is considered to be a more accurate way to describe the outlook for patients with a particular type and stage of cancer.

The overall 5-year relative survival rate for all patients with anal cancer is 58% for men and 69% for women. For localized stage, the relative 5-year survival is around 80%. For cancers in the regional stage, this rate is about 57%. In those with distant disease, this rate is about 17%. In all stages, the survival rate is slightly higher for women than for men.

Of course, 5-year survival rates are based on patients first diagnosed and treated more than 5 years ago. Recent improvements in treatment may result in a more favorable outlook for recently diagnosed patients.