How Is Anal Cancer Staged
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.
Staging of anal cancer uses a system created by the American Joint Committee on Cancer (AJCC). The staging description that follows applies only to anal canal tumors.
The TNM System
The TNM system for staging contains three 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 (metastasis) to nearby (regional) lymph nodes
- M indicates whether the cancer has metastasized (spread) to other organs of the body
Additional letters or numbers 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 “i” and “s” mean “carcinoma in situ,” which means the tumor is contained within the layer of anal tissue in which it first developed (the epithelium) and has not yet penetrated to a deeper layer of tissue.
The possible values for T are:
TX: Primary tumor cannot be assessed.
T0: No evidence of primary tumor
Tis: Carcinoma in situ
T1: The tumor is 2.0 cm (about 4/5 inch) or smaller.
T2: Tumor is larger than 2.0 but smaller than 5.0 cm (2 inches).
T3: Tumor is larger than 5 cm.
T4: Tumor of any size that invades nearby organ(s), such as the vagina, urethra (the tube that carries urine out of the bladder), or bladder
The possible values for N are:
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
The M values are:
MX: Presence of distant metastasis cannot be assessed
M0: No distant spread
M1: Distant spread to internal organs or lymph nodes of the abdomen is present.
Using the TNM system, a doctor will use each letter (T, N, and M) and a corresponding number. To make this information somewhat clearer, 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 (epithelium).
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 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, 2, or 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 not spread to lymph nodes. It has not spread to distant sites.
Stage IIIB: T4, N1, M0, Any T, N2 or 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 one groin or lymph nodes in both groins or lymph nodes in one groin and 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 means that the cancer 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 can only be approximate. They depend on reporting from institutions 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 61% for men and 73% for women. If the cancer is localized, the relative 5-year survival is around 80%. If regional, it is 60%. It is 20% for those with distant disease. In all cases, the survival is slightly higher for women and lower for men.
The 5-year survival rate refers to the percentage 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 prognosis. Five-year relative survival rates don’t include patients dying of other diseases.
Five-year relative survival rates are considered to be a more accurate way to describe the prognosis for patients with a particular type and stage of cancer. Of course, 5-year survival rates are based on patients diagnosed and initially treated more than 5 years ago. Recent improvements in treatment often result in a more favorable outlook for recently diagnosed patients.