Anal cancer stage II is a diagnosis that refers to a tumor that has grown larger than 2 centimeters but has not yet spread to nearby lymph nodes or other parts of the body. Understanding this stage can help patients and their families navigate treatment options and know what to expect during the journey ahead.

What Does Stage II Anal Cancer Mean?

Stage II anal cancer is divided into two groups based on the size of the tumor. In stage 2A, the cancer measures larger than 2 centimeters but no bigger than 5 centimeters. In stage 2B, the cancer has grown larger than 5 centimeters. In both cases, the cancer has not spread to any nearby tissues, lymph nodes, or other organs in the body.^[1]

Doctors use a system called TNM staging to describe anal cancer in detail. This stands for tumor, node, and metastasis. The T describes the size of the tumor, N describes whether cancer cells are in nearby lymph nodes, and M describes whether the cancer has spread elsewhere in the body. Stage 2A is the same as T2, N0, M0 in the TNM system, while stage 2B corresponds to T3, N0, M0.^[1]

Most anal cancers are squamous cell cancers, which is the most common type that starts in the cells lining the anal canal. The information about stage II typically refers to this type of anal cancer.^[1]

Causes of Anal Cancer

Anal cancer develops when cells in the tissues of the anus or anal canal undergo certain changes in the way they function, particularly in how they grow and divide. The anus is the end of the large intestine where solid waste leaves the body. The anal canal connects the rectum to the anus and is about 1 to 1½ inches long.^[7]

Most anal cancers are linked to infection with certain strains of human papillomavirus, commonly known as HPV. The same high-risk strains of HPV that can lead to cervical cancer can also cause anal cancer, especially HPV types 16 and 18. HPV infection is very common and usually does not cause symptoms, so most people who have it are completely unaware.^[3]

It is important to understand that not everyone with HPV will develop anal cancer, and not everyone with anal cancer has HPV. The development of cancer involves many factors and changes at the cellular level that can take years to occur.^[3]

Risk Factors

Several factors can increase a person’s chance of developing anal cancer. A risk factor is anything that raises the likelihood of getting a disease, though having one or more risk factors does not mean a person will definitely develop cancer. Many people with risk factors never get anal cancer, while others with no known risk factors do develop the disease.^[7]

Being infected with high-risk strains of HPV, particularly types 16 or 18, is a major risk factor. Engaging in unprotected anal sex as the receiving partner increases the risk for both HPV infection and anal cancer, regardless of a person’s sex. Having many sexual partners further increases the risk.^[3]

People who have not been vaccinated against HPV have a higher risk because the vaccine protects against the strains of HPV that are linked to cancer. The HPV vaccine can prevent not only anal cancer but also cancers of the mouth and throat, cervical cancer, and penile cancer.^[3]

Having a weakened immune system significantly increases the risk of anal cancer. This includes people living with HIV, which weakens the immune system and makes it less able to fight off viruses like HPV. Some people with anal cancer have both HPV and HIV infections. Other conditions that weaken the immune system, as well as medicines that suppress immune response, can also raise the risk.^[3]

A personal history of cancers affecting the genitals, especially vulvar, vaginal, or cervical cancer, increases the likelihood of developing anal cancer. Smoking is another important risk factor, as people who smoke are more likely to develop cancer of all kinds.^[3]

Symptoms

The symptoms of anal cancer can sometimes be similar to those of more common conditions like hemorrhoids, which is why it is important to see a healthcare provider if symptoms persist or worsen. The most common symptom is rectal bleeding or bloody stools.^[3]

People with anal cancer may experience pain or a feeling of fullness in the anal area that feels like constantly needing to have a bowel movement. Changes in bowel habits, such as having thinner stools than usual, can also occur. A lump or mass may be visible or felt at the anal opening.^[3]

Other symptoms include itching around the anus or discharge from the anus. Having one or more of these symptoms does not automatically mean a person has anal cancer, but it is important to talk to a healthcare provider if things do not improve within a few days or if symptoms get worse.^[3]

Prevention

While there is no guaranteed way to prevent anal cancer, there are several steps people can take to reduce their chances of developing the disease. Quitting smoking or never starting is one of the most important preventive measures, as smoking increases the risk of many types of cancer, including anal cancer.^[3]

Using condoms during anal sex can help reduce the risk of HPV transmission, though it does not eliminate the risk entirely. Getting the HPV vaccine is highly recommended for those who are eligible. The vaccine is most effective when given before a person becomes sexually active, but it can still provide protection even after sexual activity has begun.^[3]

For people who have multiple risk factors, such as a weakened immune system or a history of HPV-related cancers, healthcare providers may recommend cancer screenings. These might include an anal pap test or an anal HPV test, which check a sample of tissue for abnormal cells or the presence of the HPV virus. Although healthcare providers do not typically screen for anal cancer in the general population, screenings can be helpful for high-risk individuals, especially since anal cancer does not always cause symptoms in the early stages.^[3]

How the Body Changes: Understanding Pathophysiology

In stage II anal cancer, the tumor has grown to a size that can cause noticeable changes in the body’s normal function. The cancer cells divide and multiply more rapidly than normal cells, forming a mass that can interfere with the normal activities of the anus and anal canal.

As the tumor grows, it can affect the ability of the anal sphincter muscles to function properly. These are the ring-like muscles that control the passage of stool out of the body. When cancer grows in or near these muscles, it can cause pain, discomfort, or the sensation of needing to have a bowel movement even when the bowels are empty.

The tumor can also narrow the anal canal, which is why some people with anal cancer notice that their stools become thinner. As the cancer cells continue to grow, they can cause bleeding from the delicate tissues of the anal canal, which explains why rectal bleeding is such a common symptom.

At stage II, the cancer has not yet spread to lymph nodes or other organs, meaning the abnormal cell growth is still confined to the original location. However, if left untreated, cancer cells can eventually break away and travel through the lymphatic system or bloodstream to other parts of the body, which is why treatment at this stage is so important.^[1]

Treatment for Stage II Anal Cancer

Knowing the stage of anal cancer helps doctors decide which treatment is best for each patient. Treatment decisions also depend on factors such as where the cancer is located in the anus and the patient’s general health.^[1]

The main treatment for stage 2 anal cancer is chemoradiotherapy, which means receiving both chemotherapy and radiotherapy at the same time. Chemotherapy uses anti-cancer drugs, also called cytotoxic drugs, that circulate throughout the body in the bloodstream to destroy cancer cells. Radiotherapy uses high-energy waves similar to x-rays to kill cancer cells.^[1]

During chemoradiotherapy for stage 2 anal cancer, external radiation therapy is usually given once a day, five days a week, for 5 to 6 weeks. Chemotherapy is typically given every 3 weeks. The chemotherapy drug combination most commonly used is fluorouracil (also called 5-fluorouracil or 5-FU) combined with mitomycin. Sometimes capecitabine is used instead of fluorouracil. Extra radiation doses, called a radiation boost, may also be given.^[4]

One of the important benefits of chemoradiotherapy is that it leaves the muscles of the anal sphincter in place, which means the muscles are spared from removal. If it is possible to avoid harming or removing these muscles, a patient’s overall quality of life after treatment will be better because they will be able to have bowel movements normally.^[4]

Unfortunately, chemoradiotherapy is not suitable for everyone. Doctors will discuss other treatment options if they feel it is not the best choice for a particular patient. When treatment is finished, the doctor will check to make sure the cancer has completely gone.^[1]

Some people diagnosed with anal cancer may have an abnormal opening or passage between the anus and the surrounding skin around the anus. This is called an anal fistula or perianal fistula. If a patient has an anal fistula, surgery to repair it will be needed before starting chemoradiotherapy for stage 2 anal cancer.^[4]

If the doctor thinks there are still cancer cells remaining after chemoradiotherapy, they will take a sample of tissue, called a biopsy, from the area. If the biopsy contains cancer cells, the doctor will discuss further treatment options. This may include a large operation called an abdominoperineal resection, abbreviated as APR. This type of surgery removes the rectum, anal sphincter, anus, and muscles around the anus. The surgeon and anesthetist will make sure the patient is well enough to have this surgery before proceeding.^[1]

Patients may also want to talk to their doctors about clinical trials. Clinical trials look at new ways to prevent, find, and treat cancer. These studies test new treatments or new combinations of existing treatments to see if they work better or cause fewer side effects.^[4]