Anal cancer stages

The clinical stage of anal cancer is determined during diagnosis of the disease, which may include a physical exam, imaging tests and/or biopsy. Surgical or pathological staging (if surgery has been performed) is done by examining tissue.

The most commonly used anal cancer staging system is the TNM system established by the American Joint Committee on Cancer. The TNM staging system examines three key factors to determine the stage of cancer:

T (tumor): This describes the size of the original tumor.

N (node): This indicates whether the cancer is present in the lymph nodes.

M (metastasis): This refers to whether cancer has spread to other parts of the body.

A number (0-4) or the letter X is assigned to each factor. A higher number indicates increasing severity. For instance, a T1 score indicates a smaller tumor than a T2 score. The letter X means the information could not be assessed.

Stages of anal cancer

Once the T, N and M scores have been assigned, one of the following overall anal cancer stage is assigned:

Stage 0: The cancer has not grown beyond the top layer of anal tissue and has not spread. Also called carcinoma in situ or Bowen’s disease.

Stage 1 anal cancer: The cancer has spread beyond the top layer of anal tissue, but it has not spread to nearby lymph nodes or distant sites. The tumor is less than 2 cm.

Stage 2 anal cancer: The tumor is greater than 2 cm but has not spread to nearby organs, lymph nodes or distant sites.

Stage 3 anal cancer: There are two subcategories of stage 3 anal cancer: 3A and 3B. The categories differ by the extent to which the cancer has spread.

• Stage 3A anal cancer may be staged in two different ways:

• Stage 3B cancer may also be staged in two different ways:

Stage 4 anal cancer: In this, the most advanced stage of anal cancer, the cancer is any size and may or may not have spread to nearby organs, such as the vagina or bladder. The cancer may or may not have spread to nearby lymph nodes. The cancer has spread to distant organs and tissues.

Anal cancer survival rate

One way to estimate life expectancy when battling cancer is to consider the five-year relative survival rate for that type of cancer. A five-year relative survival rate shows the likelihood that a person with a specific type and stage of cancer would live for at least five years after the diagnosis, compared with people who don't have cancer. The rate includes the life expectancy of patients who are still in treatment and those who have finished treatment and have had tests that show no evidence of disease.

The American Cancer Society reports these anal cancer survival rates:

• Localized anal cancer: If the cancer hasn’t spread outside the anal area, the five-year relative survival rate is 82 percent.
• Regional anal cancer: For patients with anal cancer that’s spread to nearby lymph nodes or structures, the five-year relative survival rate is 66 percent.
• Distant anal cancer: If the cancer has spread to distant organs or body parts (like the lungs or liver), the five-year relative survival rate is 35 percent.

Next topic: How is anal cancer diagnosed?