When staging anal cancer, doctors consider the size of your tumor, and whether it has spread to nearby organs and lymph nodes, or distant organs. Stage 3 is diagnosed when the tumor extends into surrounding organs or lymph nodes but not distant organs.

Anal cancer is a rare type of cancer that develops in your anus. The American Cancer Society (ACS) estimates 9,760 cases will be diagnosed in the United States in 2023. Upwards of 90% of people with a diagnosis of anal cancer are positive for human papillomavirus (HPV).

Doctors stage anal cancer to help guide treatment decisions and predict your chances of survival. The most common staging system is the American Joint Committee on Cancer (AJCC)’s TNM system. This system divides anal cancer from stage 0 to stage 4.

Stage 3 anal cancer, also known as stage III, means that your cancer has either spread into nearby tissues or lymph nodes. Most people with stage 3 cancer live at least 5 years.

Read on to learn more about stage 3 cancer including how it’s staged and treated.

Is stage 3 anal cancer curable?

Stage 3 anal cancer is often curable. Doctors often consider your cancer cured if there are no signs of cancer for at least 5 years. The chances of curing anal cancer are generally best in people who are younger or are in better overall health.

Learn more about curing anal cancer.

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The AJCC’s TNM system considers three factors when staging anal cancer:

  • Tumor, the size of your tumor
  • Nodes, whether your cancer has spread into nearby lymph nodes
  • Metastasized, whether your cancer has spread to distant body parts

Doctors can find out which stage you’re in by taking a small tissue sample during a procedure called a biopsy, and performing imaging to see if your cancer has spread to other areas.

Your doctor will diagnose you with stage 3 anal cancer if the tumor extends into nearby organs, lymph nodes, or both.

Stage 3 anal cancer vs. regional anal cancer

The National Cancer Institute (NCI) and ACS use a different staging system for reporting survival statistics. They break anal cancer into three stages:

  • Localized: This is if the cancer is contained to your anus.
  • Regional: This is if the cancer has spread into nearby structures or lymph nodes.
  • Distant: This is if the cancer has spread to distant body parts.

Regional cancer in this staging system is equivalent to stage 3 in the AJCC system. According to data from the NCI’s SEER program, 33% of anal cancers diagnosed in the United States between 2010 and 2019 were regional.

Doctors subdivide stage 3 anal cancer into three categories depending on how far your cancer has spread.

Stage 3A anal cancer

Your doctor will diagnose you with stage 3A anal cancer if your tumor is 2 centimeters (0.8 inches) across or smaller, and has spread to lymph nodes near the rectum but not to distant parts of your body.

Stage 3B anal cancer

Stage 3B anal cancer occurs when your tumor has started to grow into nearby organs, such as your:

  • vagina
  • urethra
  • prostate gland
  • bladder

Stage 3B anal cancer still hasn’t spread to lymph nodes or distant body parts.

Stage 3C anal cancer

Your doctor will diagnose you with stage 3C anal cancer if your cancer is 5 centimeters (2 inches) across or larger, and has spread to neighboring organs (such as the vagina, urethra, prostate gland, or bladder) and nearby lymph nodes but not distant body parts.

Stage 3 anal cancer is usually treated with external beam radiation therapy and chemotherapy. When these treatments are combined, they’re called chemoradiation therapy.

The most common combination of chemotherapy drugs is fluorouracil (5-FU) with mitomycin. Some people receive capecitabine (Xeloda) instead of 5-FU. It can take up to 6 months to see the full effects of your treatment.

If chemoradiation therapy isn’t effective, your doctor may recommend a type of surgery called abdominoperineal resection. During this procedure, a surgeon removes your:

  • anus
  • rectum
  • lower large intestines
  • possibly lymph nodes

The end of your remaining intestines is attached to your abdomen, where waste is collected in a bag outside your body.

The relative 5-year survival rate of regional anal cancer is about 35%. This means that people with stage 3 anal cancer are about 35% as likely to live at least 5 years compared with people in the general population.

Factors linked to a better outlook include:

  • younger age
  • lower HPV load (HPV infection often causes anal cancer)
  • better overall health
  • female sex

Here’s a look at how the relative survival rate for stage 3 anal cancer compares with the relative survival rates for other stages.

Stage5-year relative survival rate
Localized82%
Regional66%
Distant35%
All stages69%

Learn more about anal cancer outlook.

Here’s a brief look at the AJCC stages of anal cancer.

Cancer stageDescription
Stage 0Pre-cancerous cells are growing in the lining of your anus.
Stage 1Your cancer is contained to your anus and is smaller than 2 centimeters (0.8 inches) across.
Stage 2Your cancer is smaller than 5 centimeters (2 inches) across and still contained to your anus.
Stage 3Your cancer has either spread to nearby organs or to nearby lymph nodes.
Stage 4Your cancer has spread to distant parts of your body.

Learn more about anal cancer stages here.

Stage 3 anal cancer occurs when cancer spreads to nearby organs, lymph nodes, or both. It can often be treated with a combination of chemotherapy and radiation therapy. You may need surgery if these treatments aren’t effective.

Many people find it embarrassing to visit their doctor with a problem with their anus, but it’s critical to seek immediate medical attention if you develop any anal cancer warning signs for a prompt diagnosis and treatment.

Learn more about anal cancer symptoms here.