Anal cancer is a rare form of malignant tumor of the anal canal, the terminal portion of the digestive tract measuring three to four (3-4) cm, located between the rectum and the skin of the anal margin. Anal cancer should not be confused with rectal cancer, which is a cancer of the gastrointestinal tract that develops from the lining of the large intestine.
The anal canal is surrounded with three types of cells that line its cavity and surface (Epithelia); each of which can be affected by a particular type of cancer, which explains why there are different types of anal cancers. Squamous Cell Carcinoma is often caused by infection from Human Papilloma-Virus type 16 and 18, Cloacogenic Carcinoma; a rare form of cancer of the anus presents the same symptoms with Squamous Cell Carcinoma and requires the same treatment. Adenocarcinoma is a rare form of anal cancer arising from the glandular cells. Among these three, Squamous Cell Carcinoma is the most common.
Anal cancer represents less than 2% of gastrointestinal cancers, and 6% of Ano-rectal cancers. Its incidence seems to be higher among women, people aged 60 years or older, and homosexuals infected with human immunodeficiency virus (HIV).
In recent years, the incidence of anal cancer has increased. It is estimated that in 2008 about 5,070 new cases of anal cancer were diagnosed in the United States alone, with an estimated total of about 3,000 in women and 2,000 in men. The number of deaths was estimated at 680; two-thirds of those patients were over 65 years old.
The anus is the opening through which the terminal portion of the large intestine (colon) joins the outside of the body. It plays many important roles among which is the expulsion of faeces and bloating. The anus contains a group of muscular fibres called “Sphincter-Ani-Externus”, which means external anal sphincter. The sphincter is endowed with cells that allow the anal cavity to open during defecation (expulsion of faeces from inside the rectum), and remain closed during normal times (periods of non-defecation).
Anal cancer is due to the genetic mutation of cells that line the cavity and the surface of the anus. Which means you are likely to have anal cancer when healthy cells in your anal cavity, turn into abnormal cells and multiply chaotically. The causes of this abnormal cellular proliferation are not well known to scientists, but some suspected risk factors have been discovered
3. Risk factors.
The most common risk factors of anal cancer include:
- Human Papillomavirus (HPV type 6) – HPV infection is a major causative factor of cervical and anal cancer. HPV 6 was identified in several studies as a degenerative factor of the cells that line the surface of the anal cavity. If left untreated, this degeneration can lead to the onset of cancer in some people. The virus is transmitted most frequently by direct skin to skin contact or mucous to mucous exchange during sexual intercourse. Therefore, unsafe sex is a major risk for developing anal cancer.
- Sex – Although anal cancer affects both men and women, it is predominant common in women. Several studies have revealed that women are more exposed to developing anal cancer than men with the exception of homosexual men who are more prone to the ailment.
- Anal sex – If you practice anal sex, your risk of having HPV infection and anal cancer is higher. This risk concerns not only homosexuals, but also heterosexual couples who engage in anal sexual activities. However, gays are more often diagnosed with Anorectal diseases.
- HIV / AIDS – People who are infected with human immunodeficiency virus (HIV), or having a history of genital warts have an increased risk of anal cancer.
- Smoking – This might sound odd, but smoking may also promote the development of anal cancer.
- Polygamy – Having multiple sexual partners, increases your exposure to anal cancer, HIV/AIDS, HPV infection, and all other STDs.
- Immune Suppressive Drugs – taking Immunosuppressive drugs or immune-suppressive agents such As corticosteroid for a long period of time places you at risk of developing all types of cancer.
If you have anal cancer, you are likely to experience at least one of the following symptoms:
- Lumps around the anus
- Rectal bleeding.
- Anal Itching or unusual discharge.
- Constipation followed by diarrhoea.
- Excess bloating, sudden change in bowel activity and painful defecation
- Some women may also experience vaginal dryness and lower back pain due to the pressure of a tumour on the vagina.
Several pieces of research have proven that about 70% of patients with anal cancer are effectively treated with non-surgical treatment methods with no known no complications. However, in some patients, the tumour persists even after radiotherapy and chemotherapy which spread on from its primary site into other parts of the body this type of abnormality are called metastatic anal cancer.
Metastatic anal cancer is rare; cancer can spread to your liver even the lungs, and become life-threatening. In general, if you have anal cancer your five-year survival rate is low.
Regular medical visits allow your doctor to do regular medical examination and evaluation of your anus, which allows the detection of early cancerous lesions before they become cancerous a normal anal Pap smear can help detect precancerous changes. If you have pain or chronic rectal bleeding, your doctor may recommend an examination of your anal canal. However, to confirm the diagnosis the following tests will be performed.
- Digital Rectal Exam (DRE) – To examine your anal cavity, your doctor may insert a gloved finger into your anal canal to detect abnormalities such as lumps. However, this is not sufficient enough to detect anal cancer, but to provide the physician with an overview of the health status of your anus so that he can proceed with more specific tests.
- Anoscopy– An anoscopy is a procedure commonly performed to visualize the anus, anal canal, and lower rectum. The method consists of inserting a lubricated instrument called anoscope into the anus to directly view the lining of the anal canal and lower rectum. An anoscope is painless and requires no complicated preparations; however, for most patients, the procedure can be uncomfortable. Depending on the severity of the disease in your anus your health care provider may perform a sort of special anoscope called a High-Resolution Anoscopy (HRA); a form of anoscope consisting of using an amplifier to get more detailed images of your anal mucosa.
- Ultrasound (Sonography)– In some cases, your physician may perform an anal ultrasound to examine your anal tissue. During the procedure, a probe will be inserted into your anal canal, which visualizes the images of your anus, and eventually reveals fistula or formation of scar tissue.
- Biopsy – Depending on the results of the exams, mostly if lesions and tumours are found in your anal canal, your doctor may take samples of your anal tissue to be examined under a microscope. A pathologist will examine the sample to confirm or exclude a diagnosis of anal cancer. In case cancer has spread outside the anus, it can be detected using a CT (scan) or MRI (Magnetic Resonance Imaging).
Once the presence of the cancer is confirmed in your anus, your doctor will perform other medical procedures to determine its current stage. The staging test is not only important to have an idea of the severity of a tumour but also to determine the best treatment to implore. Usually, anal cancer progresses in the following stages:
- Carcinoma in situ– also called Stage 0, the carcinoma in situ indicates the genesis of the cancer cells. Stage 0 anal cancer represents a minor threat and barely causes known symptoms.
- Stage I – during this period, the tumour is usually less than two centimetres in diameter at this stage, anal cancer has infected the muscle tissue of the sphincter, and tend to be symptomatic
- Stage II – anal cancer is characterized by an increased size of a tumour, usually larger than two centimetres in diameter. Cancer would have spread beyond the top layer of the anal tissue, but usually not affecting nearby organs.
- Stage IIIA –During this phase, anal cancer has increased in size, and has spread beyond the anal canal to affect nearby organs such as the bladder, urethra or vagina.
- Stage IIIB –At this stage, anal cancer has increased considerably in size. It has spread beyond the anal canal and can affect the lymph nodes around the rectum, in the groin or in the abdomen. The symptoms become severe.
- Stage IV–The cancer cells at this final stage, has spread from the anal area to distant parts such as the liver and lungs. A Stage IV anal cancer usually causes serious and more severe symptoms.
When diagnosed early, anal cancer can be completely cured since it can be treated via surgery or a combination of chemotherapy and radiotherapy. However, all forms of treatment are subject to inconveniences. Surgery always consists of removing the anal sphincter; chemotherapy and radiation treatments can lead to complete healing without the removal of the sphincter; however, they always cause side effects, which may last a lifetime.
Anal cancer can be effectively treated with chemotherapy drugs such as Mitomycin and Fluorouracil for instance. These medications are most often taken intravenously to kill or slow down the proliferation of cancerous cells. Since cancer is characterized by uncontrolled cell division, these drugs work by acting on DNA, on RNA or the proteins of cells to block certain stages of their division. However, all chemotherapy drugs always attack healthy cells that multiply rapidly which lead to side effects in most patients such as:
- Soreness of the mouth
- Weight loss
- Decreased appetite
- Bladder inflammation
- Dry mouth
- Hair loss
- Lung problems (rare).
Radiation therapy involves exposing the anus to electromagnetic waves to destroy or slow down the multiplication of cancer cells. Radiotherapy can treat and even eliminate cancer without surgery. The exposure of ionizing radiation on large tumour does not only reduce symptom but also allows the preservation of the anal sphincter, unlike surgical treatment. In most cases, the radiation lasts for about four weeks, four or five times per week, Monday through Friday.
Your Oncologist can recommend external beam radiotherapy or internal radiotherapy (Brachytherapy). Depending on your condition, both methods can be used.
However, unlike chemotherapy, radiation therapy kills both cancer cells and normal cells surrounding the tumour, which can lead to:
- Anal bleeding
- Burn in the anal area
- Hardening of certain tissue of the anus
- Anal incontinence(involuntary loss of gas or/and faecal matter)
- Significant narrowing of the anus (rare).
- Surgical Treatment.
Surgery is reserved for advanced anal cancer or in cases of failure of radio-chemotherapy treatments. Like cancer treatments, surgical therapy has its inconveniences, the healing of the perineum (the area of the body located between the anus and the scrotum in men and between the anus and the vulva in women) is always long and an arduous journey.
In the early stage of anal cancer, your surgeon can decide to remove the cancerous tissue without removing or damaging the anal sphincter. In this case, the surgery aims at stopping the progression of a tumour, therefore increasing the effectiveness of chemotherapy and radiation therapy.
Abdominoperineal resection (abdominoperineal excision) – In the advanced stage of anal cancer or in case of failure of radiotherapy and chemotherapy, The removal of the anus, the rectum, and part of the sigmoid colon will be the only option to get rid of anal cancer. However, the surgery can be inconvenient, hence rarely performed.
Prognosis of anal cancer, depending on the initial stage of a tumour, lifestyle, and age. According to the National Cancer Institute (NCI), from 2002-2006, the median age at death for cancer of the anus, anal canal, and anorectum was 65 years of age
In small tumours detected at an early stage, the 5-year survival rate was obtained in 85 to 90% of cases. Nevertheless, the survival rate is only 20 to 40% for stage 3 and 4 tumours. According to the same Institute, the overall 5-year relative survival rate from 1999-2005 was 66.3%, while the five-year relative survival rates by race and sex were as follows:
- 61.8% for white men.
- 70.3% for white women.
- 53.7% for black men.
- 65.7% for black women.
The prevention of anal cancer consists of lots of measures which include the elimination of the potentially known risk factors and getting vaccinated against HPV viruses and other habits capable of exposing one to the HPV viruses such as:
- Unsafe sex
- Multiple sexual partners
- Anal sex
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