Staging, the process of finding out how far the cancer has spread, is very important because your treatment options and the outlook for your recovery and survival depend on the stage of your cancer. 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.

The TNM System

The TNM system for staging contains 3 key pieces of information:

• T describes the size of the primary tumor, measured in centimeters (cm), and whether the cancer has spread to organs next to the tumor
• N describes the extent of spread to nearby (regional) lymph nodes
• M indicates whether the cancer has metastasized (spread) to other organs of the body

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

• The numbers 0 through 4 indicate increasing severity.
• The letter X means "cannot be assessed" because the information is not available.
• The letters "is" mean "carcinoma in situ," which means the tumor is contained within the top layer of anal tissue and has not yet reached deeper layers of tissue.

The possible values for T are:

The possible values for N are:

The M values are:

Stage Grouping

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

Stage 0 (carcinoma in situ): Tis, N0, M0: Stage 0 is very early cancer that exists only in the top layer of anal tissue.

Stage I: T1, N0, M0: The cancer has spread beyond the top layer of anal tissue but 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, 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 has spread to the lymph nodes around the rectum, or it has grown into nearby organs such as the vagina or the bladder but has not spread to lymph nodes. It has not spread to distant sites.

Stage IIIB: T4, N1, M0, or Any T, N2 -3, M0: The cancer has grown into nearby organs, such as the vagina or the bladder, and has 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: Cancer can be any size and may or may not have spread to lymph nodes but has spread to organs in other parts of the body.

Recurrent: Recurrent anal cancer is cancer that has come back (recurred) after treatment in either the anus or in another part of the body.

Five-Year Survival by Stage

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 staging system looks at whether the cancer is localized (corresponds roughly to stages I and II), regional, (corresponds roughly to stage IIIA), or distant (corresponds roughly to stages IIIB and IV).

The overall 5-year relative survival for all patients is 60% for men and 71% for women. If the cancer is localized, the relative 5-year survival is around 82%. If regional, it is 60%. In those with distant disease, this rate is about 19%. In all cases, the survival rate is slightly higher for women than for men.

The 5-year survival rate refers to the portion of patients who live at least 5 years after their cancer is diagnosed. Although many of these patients live much longer than 5 years after diagnosis, 5-year rates are used to produce a standard way of discussing outcomes. Five-year relative survival rates assumes that people with anal cancer will die of other causes and compares the observed survival with that expected for people with and without anal cancer. That means that relative survival only reflects deaths from anal cancer.. Five-year relative survival rates are considered to be a more accurate way to describe the outlook for patients with a particular type and stage of cancer.

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