Anal cancer

Anal cancer is a condition characterized by the growth of cancerous tissues in the anus. The anus is present at the end of the rectum, through which stool or solid waste is passed out from the body. Anal cancers account for 1-2% of total intestines cancer. Two-thirds of anal cancer affects women. Anal cancers are mainly of 2 types based on where they start:

1. Anal canal cancer (above anal verge)
2. Perianal skin anal cancer (below anal verge). 

The anal verge is where the anal canal connects to the outer skin at the anus.

Most patients do not experience any symptoms of anal cancer in the early stages. However, bleeding is the first common symptom of anal cancer. Some of the symptoms of anal cancer are:

1. Abnormal discharge from the anus
2. Pain in the anal area
3. A lump at the anal opening
4. Loss of bowel control leading to faecal incontinence
5. Discomfort and itching around the rectum
6. Swelling in the anus area 
7. Change in the bowel movements
8. Leaking or loose stools

The actual cause of anal cancer is still unknown. Anal cancer is caused due to uncontrolled cell division in the anal region. These cells grow abnormally and start accumulating, forming masses called a tumour. Later, the tumour spreads to other body parts, affecting vital body functions.

Anal cancer is related to a Sexually Transmitted Infection called HPV (Human Papillomavirus). It also develops when cancer spreads from different parts to the anus. It is known as cancer metastasis.

Risk Factors

Anal cancer may develop in people of all ages and sex. However, many factors increase the chances of anal cancer. Some of the risk factors are:

1. Age ( 55 years and older)
2. Multiple sex partners
3. Smoking and drinking habits
4. Sexually transmitted diseases like human Papillomavirus infection, 
5. Anal sex
6. Patients with a weak immune system who are mainly on immunosuppressant medications (such as organ transplants).
7. Prior history of cancer (patients who had cervical or vaginal cancer in the past)
8. Abnormal opening such as open wounds and fistulas in the anal area
9. Radiation therapy for prostate, rectal, bladder, or cervical cancer

The doctor may diagnose anal cancer through any of the following tests and procedures:

1. Patient’s history and physical examination: The doctor will ask questions about your medical history, lifestyle, bowel movement, previous treatment, diseases, and family history. 
2. Digital rectal examination (DRE): The doctor or nurse inserts a lubricated, gloved finger in the anus or rectum during this procedure. It is done to check for the lumps. 
3. Anoscopy:  It is performed to take a closer look at the anus. The doctor inserts a thin, flexible tube to examine the inner lining of the anal canal.
4. Proctoscopy: In this method, a proctoscope instrument (consisting of the lens) is inserted into the body to check any abnormality in the anus and rectum. It also removes the tissue, which is sent for further examination. 
5. Biopsy: Obtaining a small tissue sample for examination under a microscope by a pathologist is called a biopsy. The type of biopsy depends on the location of the cells/tissues.
6. Ultrasound: In this technique, sound waves create images of the anal region. The ultrasound transducer is inserted in the anus for Endo-anus ultrasound.
7. Computed tomography scan: It is also known as CT scan. It can determine the location and tumour size by developing a 3D image of the tumour.
8. Magnetic Resonance Imaging (MRI): A magnetic field is used to get a detailed image in this technique. A special dye is used in MRI to obtain a clearer picture.
9. PET Scan: The doctor may also advise the patients to undergo a PET scan for diagnosing anal cancer.
10. Pelvic exam: The doctor may also perform a pelvic exam in women to determine the presence of anal cancer. The doctor inserts a speculum into the vagina to look for signs of anal cancer.
11. Papanicolau (Pap) test: The patients may also undergo an anal pap test. During this test, the doctor collects cell samples by inserting a swab in the anus. The sample is then evaluated under the microscope for any abnormal cells.

The treatment of cancers depends on various factors such as the size of the tumour, stage and location of anal cancer. The different types of treatments are:

Surgery for anal cancer: Anal cancer in early stages is treated by surgery. A tumour of size up to one-half inch can be removed surgically. During surgery, the cancerous cells and nearby healthy tissue is removed. It is primarily used for treating anal cancer that has not entered the anal wall. It is also called local resection.

1. Abdominoperineal resection: This process is used when cancer keeps coming back after radiation and chemotherapy. The surgeon removes the anus, the rectum, and the sigmoid colon part with nearby lymph nodes. Later, the doctor attaches a small bag outside the anus, called a stoma, to collect stools.
2. Radiation therapy:  In this process of anal cancer treatment, high-energy radiation is used. It kills cancer cells and stops their multiplication. The radiation therapy for anal cancer may continue for five to six weeks. It is of 2 types:
   1. External Radiation therapy: A machine is used to send the radiation towards the cancerous area from outside.
   2. Internal Radiation therapy: The doctor places the radioactive substances directly into or near the cancer regions.
3. Chemotherapy: The doctor may also prescribe drugs to stop cancer growth. It works by killing the cancerous cells and preventing them from multiplying. It can be taken orally or injected into the body. The doctor generally administers chemotherapy in anal cancer patients in the first and fifth weeks. The doctor may also combine chemotherapy with radiation therapy to increase the effectiveness of treatment.
4. Immunotherapy: The doctor prescribes the medications that boost, improve and restore the immunity of the body. Immunotherapy works by enhancing the immune system to fight against cancer cells. 

The different stages of anal cancer through which it progress are: 

Stage 0: The pre-cancerous cells are found in the innermost layer of the anus in this stage. These cells may develop into cancerous cells and spread to other parts.

Stage 1: In this stage, the tumour is about 2 centimetres or small in size

Stage 2: This stage is divided into stages 2A and 2B. In stage 2A, the tumour is more than 2 centimetres but smaller than 5 centimetres. In stage 2B, the cancer is greater than 5 centimetres.

Stage 3:  It is divided into stages 3A, 3B, and 3C. In stage 3A, the tumour is 5 centimetres in size. It spreads to lymph nodes of the anus region. In stage 3B, cancer spreads to other organs (such as the vagina, urethra, and bladder) but not lymph nodes. In stage 3C, the tumour spread to nearby organs and lymph nodes.

Stage 4: In this stage, the tumour spreads to lymph nodes, nearby organs, and other body organs (lungs or liver).