Treatment for Anal Cancer

Anal cancer is found in 2% of cancer cases and increases with age. People assigned female at birth (AFAB) are more likely to develop it than people assigned male at birth (AMAB).¹ Squamous cancers account for about 80% of primary anal canal cancers, while adenocarcinomas arising from glands or glandular ducts mimic the behaviour of rectum cancers. Symptoms of anal cancer include:² 

• Pain in the anal region
• Bleeding
• Constipation
• The sensation of a mass in the anus
• Itching 
• Discharge of mucous

Risk Factors for Anal Cancer:²

• Infection with human papillomavirus (HPV)
• Cigarette smoking
• Immunosuppression
• Lack of fibrous diet 
• Sexual behaviour 

Chemotherapy

During chemotherapy, drugs are used to either kill cancer cells or stop them from dividing, thus decreasing cancer cell growth. Chemotherapy administered by mouth or injected into a vein or muscle enters the bloodstream and can reach cancer cells throughout the body. This is also called systemic chemotherapy.³

Usually, a combination of two or more drugs, i.e., 5-fluorouracil (5-FU), mitomycin or cisplatin, is used depending on the age, general health and type of cancer.

Chemotherapy could be used in the following situations:

1. Before surgery: when it is combined with radiation therapy, this is known as chemoradiation and is the most common treatment for anal cancer. 
2. After surgery: to kill the cancer cells that couldn’t be taken out during the surgery. This helps to avoid the relapse or recurrence of cancer.
3. For metastasis: if cancer has spread to the lymph nodes or other parts of the body.

Common side-effects of chemotherapy are nausea and vomiting, loss of hair, mouth sores, diarrhoea, loss of appetite etc. Chemotherapy causes a reduction in the number of blood cells, resulting in pancytopenia, which leads to problems like decreased immune response and thereby increased susceptibility to infection, anaemia due to low red blood count, and easy bruising and increased bleeding due to low platelet count.⁴

Radiation therapy 

Radiation therapy kills cancer cells or prevents them from growing by using high-energy rays or other forms of radiation.⁵ 

There are two types of radiation therapy: External radiotherapy uses a machine to direct radiation towards the area where cancer has developed. Internal radiotherapy is administered using a radioactive substance sealed inside needles, seeds, wires or catheters used directly inside or near cancer. Depending on the stage and type of cancer, radiation therapy may be given in different ways. Anal cancer can be treated with both external and internal radiation therapy.

Radiation therapy is often given before and/or after surgery, often in conjunction with chemotherapy, to make it easier to operate and to reduce the size of a tumour.⁶ Radiation therapy is commonly given ahead of surgery to help remove the cancer cells, especially if it is a malignant form of cancer, making removing cancer easier, particularly if the cancer is located in a lymph node. The size of the cancer and/or location might make surgery difficult. Radiation therapy is also used to treat cancers that have spread to other organs like lungs, liver or bones.

The side effects of radiation therapy for anal cancer range from redness and blistering to peeling and blisters at the site where radiation beams were aimed.⁷ Radiation before surgery can affect wound healing. It can also cause nausea, exhaustion/faintness, inflammation of the gastrointestinal tract, sometimes accompanied by diarrhoea, painful bowel movements, blood in the stool, stool leakage or incontinence. An irritated bladder can cause symptoms like frequent urination, burning or pain when urinating, or blood in the urine. People AFAB experience vaginal irritation, and people AMAB have erection issues. 

Surgery

In local resection, the tumour and some healthy tissue surrounding the tumour are cut from the anus.⁸ Cancer that has not spread may be treat with local resection. Patients may be able to control their bowel movements following this procedure because the sphincter muscles are preserved. Local resection is usually effective in removing tumours that develop in the lower part of the anus.

Abdominoperineal resection: this procedure involves cutting an incision in the abdomen to remove part of the colon, the anus and the rectum.⁹ Intestines are sewn to an opening on the body, called a stoma, which allows body waste to be collected outside of the body using a disposable bag. Such an installation is called a colostomy. During the procedure, cancerous lymph nodes can also be removed. After radiation and chemotherapy, this procedure may be used only if cancer returns after treatment.

Some of the common side-effects of surgery are infection, bleeding, pain, delayed healing process, scar or keloid formation and adhesions in the abdomen.⁹ Surgery is suggested for small and locally advanced cancer when chemoradiation does not get rid of all the cancer cells, or it comes back, and in cases when radiotherapy cannot be given.

Radiosensitizers

Chemical or pharmaceutical compounds that increase the lethal effects of radiation are known as radiosensitizers. They are a new type of treatment being tested in clinical trials. Radiation and radiosensitizers, when combined, can have a greater ability to kill the cancer cells.¹⁰

Radiation-sensitizing agents could allow for lower radiation and chemotherapy doses or reduce the side effects of treatment. In modern clinical practice, the radiosensitizer most commonly used is 5-fluorouracil (5-FU). This therapy is relatively new, and clinical trials and research are still going on to test the efficacy of these chemicals. In future, more information will be available.

Immunotherapy

Cancer immunotherapy involves administering medications that stimulate the body's immune system to recognize and destroy cancer cells more effectively. 

It is done by changing the way the immune system works so that can track and attack cancer cells.¹¹ It is done by improving the natural defences of your immune system and by making substances in the laboratories that are just like those in your immune system. With this method, your body gets rid of the cancer cells naturally, with some help from science. These substances are cancer vaccines, immunomodulators, chimeric antigen receptor (CAR) T-cell therapy, cytokines, monoclonal antibodies and inhibitors.

Among the most common side-effects of immunotherapy treatment are:¹¹

• Chills
• Vomiting
• Weight loss
• Constipation
• Coughing
• Anorexia
• Diarrhoea
• Weakness and exhaustion
• Fever and flu-like symptoms
• Headache
• Injection site pain
• Itching
• Localized rashes and blisters
• Nausea
• Rash
• Shortness of breath

What is the best treatment option for Anal Cancer?

Radiation therapy, chemotherapy and surgery are used to treat anal cancer depending on the stage of the tumour.¹² Chemotherapy and radiotherapy are used to treat local and locally advanced anal canal tumours, while chemotherapy alone is used to treat metastatic disease. In recurrent or residual cases, surgery is still the preferred method of treatment.

Life after treatment for anal cancer

Combination therapy is most often used to treat anal cancers. In many cases of cancer that returns after nonsurgical treatment, surgery is the most effective treatment.¹³ In spite of its greater side effects, combination radiation/chemotherapy provides the highest long-term survival rates. At 5 years after completing this treatment, 70-90% of patients are still alive and cancer-free.

Having your colon and rectal surgeon perform a careful examination every few months is important. During the appointment, your surgeon will evaluate the treatment results and look for any new indications of anal cancer.