After an anal cancer diagnosis, “staging” occurs which is where doctors try to determine how large the cancer is and if it has spread. This helps determine the best course of treatment. To explore the basics of what anal cancer is, including symptoms and risk factors, visit our anal cancer overview page.
By understanding the different stages of anal cancer, patients and their loved ones can better comprehend the extent of the disease and the potential treatment options available to them.
TNM staging
The most common staging system is the American Joint Committee on Cancer (AJCC) TNM system. This is based on 3 key pieces of information:
- Tumor: What is the size of the main tumor (T)? Has it grown into (or metastasized) nearby organs?
- Nodes: Has the cancer spread to nearby lymph nodes (N)
- Metastasis: Has the cancer metastasized (M, meaning spread) to distant lymph nodes or distant organs such as the liver or lungs?
Combining TNM Categories to Determine Stage
Numbers/letters after T, N, and M provide more details about each of the three pieces of information. Higher numbers mean the cancer is more advanced.
Once you have your T, N, and M categories the information is combined to assign an overall stage.
The American Cancer Society has a helpful graphic to help explain the various combinations of staging.
Anal intraepithelial neoplasia (AIN)
All growths and abnormal changes in the epithelial (skin) cells in and around the anal area are known as AIN (anal intraepithelial neoplasia). These changes are associated with infection with HPV (the human papillomavirus), which is a risk factor for anal cancer. AIN is not cancer however, it is also known as precancer.
Stage 1 anal cancer
This indicates that the tumor is 2 cm or smaller, and it has not spread to the lymph nodes or other parts of the body. It is staged as T1, N0, M0.
Stage 2 anal cancer
Stage 2 means that the tumor is larger than 2 cm, but has not spread to nearby organs, lymph nodes, or to other parts of the body. It is staged as T2 or T3, N0, M0.
Stage 3 anal cancer
- Stage 3A: The tumor is 5 cm or smaller and has not invaded nearby organs. However, there is spread to nearby lymph nodes. This is staged T1 or T2, N1, M0.
- Stage 3B: The tumor has invaded nearby organs, but there is still no spread to lymph nodes or distant orange. It is staged T4, N0, M0.
- Stage 3C: The tumor is 5 cm larger and/or has invaded nearby organs, and it has spread to nearby lymph nodes. It has not spread to distant organs. This is staged T3 or T4, N1, M0.
Stage 4 anal cancer
This indicates that the tumor has spread to the lymph nodes and to distant organs. It can be any size (so any T, any M, and M1).
Anal cancer grading
- Your doctor may also describe anal cancer by its grade (G). This describes how much cancer cells look like healthy cells under a microscope. The grade can help predict how quickly the cancer may spread. Generally, a lower grade means a better prognosis.
- To determine this, cancerous cells are compared with healthy tissue, which usually contains many different types of cells, all grouped together.
- If the cancer looks similar to healthy tissue, it is called “differentiated” or a “low-grade tumor.”
- If the cancerous tissue does not look like healthy cells, it is termed “poorly differentiated” or a “high-grade tumor.”
Prognosis
Information from the Surveillance, Epidemiology, and End Results (SEER) database, maintained by the National Cancer Institute (NCI) is a trusted source of survival statistics. It tracks 5-year relative survival rates for anal cancer in the United States, based on how far the cancer has spread. The SEER database groups cancers into localized, regional, and distant stages (not by stage):
- Localized: There is no sign that the cancer has spread outside of the anal area.
- Regional: The cancer has spread outside the anal area to nearby structures or lymph nodes.
- Distant: The cancer has spread to distant parts of the body, such as the liver or lungs.
Anal Cancer treatment by stages
The treatment regimens for anal cancer are primarily for squamous cell carcinoma, which accounts for more than 90% of all anal cancers.
For stages I – III, the standard protocol is radiation and chemotherapy, used in conjunction with one another (often called 'chemoradiation'). This combination is known as the Nigro Protocol. The Nigro Protocol typically includes several weeks of radiation with two different types of chemotherapy given at the beginning and end of treatment.
Learn more about the side effects of chemotherapy and radiation.
Surgery can be used for early-stage anal cancer when the tumor is extremely small and localized.
Stage IV cancers are usually addressed with chemotherapy alone first. Learn more about treatment for recurrent and advanced anal cancers.
Other resources
- Learn more about Immunotherapy and Clinical Trials for anal cancer.
- Check out the sessions on treatment for metastatic anal cancer treatment from our 2023 patient summit.
After an anal cancer diagnosis, “staging” takes place. This is where doctors try to determine how large the cancer is and whether it has spread. This helps determine the most appropriate course of treatment. To explore the basics of what anal cancer is, including symptoms and risk factors, visit our anal cancer overview page.
By understanding the different stages of anal cancer, patients and their loved ones can better comprehend the extent of the disease and the potential treatment options available to them.
TNM staging
The most common staging system is the American Joint Committee on Cancer (AJCC) TNM system. This is based on 3 key pieces of information:
- Tumour: What is the size of the main tumour (T)? Has it grown into (or metastasized) nearby organs?
- Nodes: Has the cancer spread to nearby lymph nodes (N)
- Metastasis: Has the cancer metastasized (M, meaning spread) to distant lymph nodes or distant organs such as the liver or lungs?
Combining TNM Categories to Determine Stage
Numbers or letters after T, N, and M provide more details about each of the three pieces of information. Higher numbers mean the cancer is more advanced.
Once you have your T, N, and M categories the information is combined to assign an overall stage.
The American Cancer Society has a helpful graphic explaining the various combinations of staging.
Anal intraepithelial neoplasia (AIN)
All growths and abnormal changes in the epithelial (skin) cells in and around the anal area are known as AIN (anal intraepithelial neoplasia). These changes are associated with infection with HPV, the human papillomavirus, which is a risk factor for anal cancer.
AIN is not cancer. However, it is sometimes described as a precancerous condition.
Stage 1 anal cancer
Stage 1 anal cancer means the tumour is 2 cm or smaller, and it has not spread to the lymph nodes or other parts of the body. It is staged as T1, N0, M0.
Stage 2 anal cancer
Stage 2 anal cancer means that the tumour is larger than 2 cm, but has not spread to nearby organs, lymph nodes, or to other parts of the body. It is staged as T2 or T3, N0, M0.
Stage 3 anal cancer
- Stage 3A: The tumour is 5 cm or smaller and has not invaded nearby organs. However, it has spread to nearby lymph nodes. This is staged as T1 or T2, N1, M0.
- Stage 3B: The tumour has invaded nearby organs, but there is still no spread to lymph nodes or distant organs. It is staged as T4, N0, M0.
- Stage 3C: The tumour is 5 cm larger and/or has invaded nearby organs, and it has spread to nearby lymph nodes. It has not spread to distant organs. This is staged as T3 or T4, N1, M0.
Stage 4 anal cancer
Stage 4 anal cancer means that the cancer has spread to distant parts of the body, such as distant lymph nodes, the liver, or the lungs. The tumour can be any size. This is staged as any T, any N, M1.
Anal cancer grading
- Your doctor may also describe anal cancer by its grade (G). This describes how much cancer cells look like healthy cells under a microscope. The grade can help predict how quickly the cancer may spread. Generally, a lower grade means a better prognosis.
- To determine this, cancerous cells are compared with healthy tissue, which usually contains many different types of cells grouped together.
- If the cancer looks similar to healthy tissue, it is called “differentiated” or a “low-grade tumour.”
- If the cancerous tissue does not look like healthy cells, it is termed “poorly differentiated” or a “high-grade tumour.”
Prognosis
The prognosis for anal cancer depends on several factors, including the stage of the cancer, tumour size, whether it has spread to lymph nodes or other parts of the body, overall health and response to treatment. Survival statistics can give a general guide, but they cannot predict exactly what will happen for any one person.
Anal Cancer treatment by stages
The treatment regimens for anal cancer are primarily for squamous cell carcinoma, which accounts for more than 90% of all anal cancers.
For stages I to III, the standard treatment is radiation therapy and chemotherapy, used together. This is often called chemoradiation. This combination is known as the Nigro Protocol. The Nigro Protocol typically includes several weeks of radiotherapy, with two different types of chemotherapy given at the beginning and end of treatment.
Learn more about the side effects of chemotherapy and radiation.
Surgery can be used for early-stage anal cancer when the tumour is extremely small and localised.
Stage IV cancers are usually addressed with chemotherapy alone first. Learn more about treatment for recurrent and advanced anal cancers.
Other resources
- Learn more about Immunotherapy and Clinical Trials for anal cancer.
- Watch the sessions on treatment for metastatic anal cancer treatment from our 2023 patient summit.
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