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Understanding Anal Cancer
Overview of Hong Kong
Anal Cancer Incidence and Survival Rate
When it comes to anal diseases, many people think of haemorrhoids, but there is a more serious condition—anal cancer. Anal cancer is a relatively rare type of cancer. Since the anus is located at the junction of the inner and outer germ layers, the types of tumors are more complex. According to data from the American Cancer Society, anal cancer can be categorised as follows:
- Squamous Cell Carcinoma: which originates from the squamous cells of most of the anal canal and the anal margin.
- Basal Cell Carcinoma: a type of skin cancer that can develop in the perianal skin.
- Melanoma: which originates from cells in the skin or the inner layer of the anus.
- Adenocarcinoma: which originates from cells near the rectum in the upper part of the anus, glands under the anal mucosa, and apocrine glands (a type of sweat gland in the perianal skin).
Although anal cancer is relatively rare, there has been an increasing trend in recent years. The American Cancer Society estimates that there will be about 9,090 new cases in 2021. Anal cancer rarely occurs in individuals under the age of 35, and the risk increases with age, with an average diagnosis age of around 60.
Despite its rarity, the threat of anal cancer should not be underestimated. According to a paper by American scholar Ashish A. Deshmukh, the mortality rate of anal cancer increases by 3.1% annually. However, the survival rate can still be relatively high if detected early. Data from the American Cancer Society shows that the 5-year survival rate for anal cancer is approximately 82%. If cancer cells have spread to surrounding tissues, organs, or nearby lymph nodes, the 5-year survival rate drops to 65%; if cancer cells have spread to distant parts of the body, the 5-year survival rate is only 32%.
The exact cause of anal cancer is still unknown, but the following factors can increase the risk of cancer:
- HPV Infection:
Human papillomavirus (HPV) is a virus transmitted through sexual contact, and individuals with anal intercourse experience or many sexual partners are at increased risk of HPV infection. - Weakened Immune System:
When the body’s resistance is weak, viruses such as HPV become more active. The most common cases are individuals infected with HIV, those taking immunosuppressants, or those who have undergone organ transplants. - Smoking:
Smoking reduces the immune system’s ability to resist HPV infection, and many studies have shown that smokers have an increased incidence of anal cancer.
Symptoms of Anal Cancer
Common ·Anal-Cancer Symptoms:Warning Signs of.Anal Bleeding and SensationofaForeign Body
The symptoms of anal cancer are similar to those of haemorrhoids, which can easily be overlooked. The following are the symptoms of anal cancer:
- Rectal bleeding
- Itching inside or around the rectum
- Lump or mass at the anal opening
- Pain or a feeling of fullness in the anal area
- Narrowing of stool or other changes in bowel movements
- Abnormal discharge from the anus
- Faecal incontinence (bowel incontinence)
- Swelling of lymph nodes in the anal or groin area
Common Examination Methods
Anal Cancer Diagnosis Methods: Digital Rectal Exam and Endoscopy
Many cases of anal cancer can be detected early because the symptoms of early anal cancer are apparent, such as the rectal bleeding mentioned above. Unfortunately, some anal cancers may not cause symptoms until the late stage, which can delay diagnosis. If a doctor suspects that a patient may have anal cancer, the following tests will be performed to make a more accurate diagnosis as soon as possible:
- Digital Rectal Exam:
The doctor will put on a glove and lubricate a finger, then insert it into the patient’s anus and rectum to check for any hard lumps or tumors. This is the most preliminary examination; further tests will be conducted if abnormalities are found. - Anoscopy:
The doctor will apply gel to an anoscope and then gently insert it into the anus and lower rectum. By shining a light into the tube, the doctor can observe the lower rectum and anus and can also take a biopsy sample from the abnormal area at the same time. - Rigid Sigmoidoscopy:
Similar to an anoscope but longer, a rigid sigmoidoscope allows the doctor to view the anus, rectum, and lower sigmoid colon. Before this test, it is necessary to ensure the patient’s bowel is empty so the doctor can see any abnormal areas. - Endoscopy:
An endoscope is a thin tube with a camera at the end that can view the anus, rectum, and the entire colon. It also has the function of obtaining tissue samples from inside the anal canal. - Biopsy:
If abnormal tissue growth is found during endoscopy, the doctor will take a part of it to check for cancer. If the growth is in the anal canal and the tumor is small, the doctor may try to remove the entire tumor during the biopsy. - Blood Tests:
HIV test: Since individuals with AIDS have a higher chance of being infected with the HPV virus, and HPV infection increases the risk of anal cancer, the doctor may ask the patient to undergo a blood test to confirm whether it is related to HIV. - Pap Smear (Cervical Smear):
This quick and simple test can detect abnormal changes in cervical cells. Women undergo cervical smear tests to check for early cervical cancer, and this method is also applicable to high-risk groups (such as individuals with AIDS or HPV infections), with an accuracy rate of up to 70%.
After diagnosis through the above methods, if the doctor finds that the patient has anal cancer, further tests may be conducted to determine the stage of cancer accurately. Factors in determining the early or late stage of cancer include the size of the tumour, whether it has spread, and whether it has spread to distant body tissues. The detailed stages are as follows:
| Stage | Description |
| 0 | Precancerous cells are only in the mucosa (a layer of cells inside the anus) and have not spread to nearby lymph nodes or distant sites. |
| I | The tumour is no more than 2 cm in size, nodes, or distant sites. |
| IIA | The tumour is more than 2 cm but not more than 5 cm in diameter, and cancer cells have not spread to nearby lymph nodes or distant sites. |
| IIB | The tumour is more than 5 cm in diameter, and cancer cells have not spread to nearby lymph nodes or distant sites. |
| IIIA | The tumour is no more than 2 cm in diameter, and cancer cells have spread to lymph nodes near the rectum but not to distant sites. |
| Or | |
| The tumour is more than 2 cm but not more than 5 cm in diameter, and cancer cells have spread to lymph nodes near the rectum but not to distant sites. | |
| IIIB | Tumors of any size grow into nearby organs, such as the vagina, urethra, prostate, or bladder. Cancer cells have not spread to nearby lymph nodes or distant sites. |
| IIIC | The tumour is more than 5 cm in diameter, and cancer cells have spread to lymph nodes near the rectum but not to distant sites. |
| Or | |
| Tumors of any size grow into nearby organs, such as the vagina, urethra, prostate, or bladder. Cancer cells have not spread to nearby lymph nodes or distant sites. | |
| IV | Tumours of any size may or may not grow into nearby organs. Cancer cells may have spread or not spread to nearby lymph nodes, but have spread to organs such as the liver or lungs. |
Main Treatment Methods
Anal Cancer Treatment Methods: Chemoradiation and Surgery Options
The doctor will determine the treatment plan based on the location, type, and stage (extent of spread) of the patient’s tumour, as well as considering the patient’s age and overall health condition. The key goal of treatment is to preserve the muscles of the anal sphincter, allowing the patient to control bowel movements and defecation without affecting overall quality of life.
- Anal Cancer Surgery
In most cases, surgery is not the first choice for treating anal cancer. If surgery is necessary, the type of surgery depends on the type and location of the tumour.- Local excision:
This surgery only removes the tumour and a small amount of normal tissue around the tumour. Local excision can be performed if the tumour is small and has not spread to nearby tissues or lymph nodes. In most cases, local excision can preserve the sphincter and normal bowel function. - Abdominoperineal resection (APR):
APR is a common treatment for anal cancer. The doctor will make an incision in the abdomen and then make another incision around the anus to remove the anus, rectum, and sigmoid colon. The doctor will also remove some lymph nodes in the groin area. Since the anus and anal sphincter are removed, a new opening is needed for defecation.
- Local excision:
However, nowadays, surgery can be avoided by using radiation therapy and chemotherapy. APR is now only used when other treatments are ineffective or when cancer recurs.
- Radiation Therapy
Radiation therapy uses rays to kill cancer cells, that is, aiming a beam of radiation at cancer cells. The doctor will choose different types of radiation therapy based on factors such as the stage of anal cancer:- External beam therapy:
High-energy rays are aimed at the tumour from outside the body to kill cancer cells. Newer technologies now provide higher doses of radiation while reducing damage to nearby healthy tissues. - Three-dimensional conformal radiotherapy (3D-CRT):
This uses a special computer to map the location of the cancer precisely and then aims rays at the tumour from multiple directions. This helps to minimise damage to normal tissues. - Intensity-modulated radiation therapy (IMRT):
This is a 3D treatment. It uses a computer-driven machine that rotates around the patient while emitting radiation. In addition to changing the beam’s shape, it can aim at the tumour from multiple angles and adjust its intensity. This helps to limit the dose reaching normal tissues and can reduce side effects. - Stereotactic body radiation therapy (SBRT):
This type of radiation can be used if anal cancer recurs in the exact location or nearby lymph nodes.
- External beam therapy:
- Brachytherapy (internal radiation):
Brachytherapy places a small amount of radioactive material inside or near the tumour. Since it focuses radiation on the cancer area, it minimises damage to nearby normal tissues. - Chemotherapy
Chemotherapy uses drugs that can destroy rapidly dividing cancer cells. For anal cancer, drugs such as 5-fluorouracil (5-FU) and mitomycin are commonly used. Since both are radiosensitisers, they can enhance the ability of radiation therapy to kill cancer cells. - Immunotherapy
Immunotherapy uses drugs to stimulate the body’s immune system to identify and destroy cancer cells more effectively.- Immune checkpoint inhibitors:
Nivolumab (Opdivo) and pembrolizumab (Keytruda) can enable the patient’s immune system to attack cancer cells, shrink tumours, or slow their growth. These drugs can be used in patients whose cancer cells have spread.
- Immune checkpoint inhibitors:
Healthy Living
Post-Anal Cancer Surgery Care: Wound Care and Bowel Habit Adjustments
After completing treatment, patients need to have regular rectal and anal examinations and check for swollen lymph nodes. More importantly, they need to check for signs of cancer recurrence. Additionally, if patients have undergone abdominoperineal resection (APR), they must attend medical training courses to learn how to care for a colostomy, such as changing the ostomy bag.
Prevention Methods
Prevention of Anal Cancer
Since the causes of many cases of anal cancer are still unclear, it is impossible to prevent this disease completely. However, we can still reduce the risk of developing anal cancer. As mentioned above, anal cancer is related to infectious viruses such as human papillomavirus (HPV) and HIV, so the public should raise awareness of safe sexual behaviour and get the HPV vaccine. In addition, smoking also increases the risk of anal cancer, so it is advisable to quit smoking immediately.
Frequently Asked Questions
Anal Cancer FAQs
What are the differences between the symptoms of Haemorrhoids and Anal Cancer?
The symptoms of haemorrhoids and anal cancer can easily be confused. The following signs can be used to distinguish them:
Signs of haemorrhoids:
- Blood in stool
- Itching, foreign body sensation in the anus
- Thrombosed external haemorrhoids can cause severe pain, and some may have surface tissue necrosis
Signs of anal cancer:
- Rectal and anal bleeding
- A hard lump or tumor can be felt at the anal opening
- Anal pain
- Abnormal itching in the anal area
- Changes in bowel habits
- Narrowing of stool shape
- Abnormal mucus discharge from the anus
- Swelling of lymph nodes around the anus or in the groin area
What should be noted before and after Anal Cancer surgery or during perianal biopsy?
Unless the patient also needs to undergo a colonoscopy, they should have a regular diet the day before surgery. If the surgery is in the morning, fasting should begin at midnight the day before; if the surgery is in the afternoon, fasting should start at 7 a.m. on the day of surgery. The patient must be admitted to the hospital for one day to undergo surgery, and an enema should be administered one hour before surgery.
What are the risks and side effects of Anal Cancer surgery?
After undergoing APR, you may have a scar on your abdomen, which can cause pain or problems with food movement in the intestines, leading to digestive issues. After APR, patients also need to undergo permanent colostomy, which means a lifestyle change. Additionally, APR may damage the ureters or urethra, making it difficult for patients to urinate.
What are the side effects of Anal Cancer radiation therapy?
Side effects vary depending on the part of the body being treated and the radiation dose. Patients may experience short-term side effects such as diarrhoea, skin changes in the treated area (similar to sunburn), anal irritation and pain, discomfort during bowel movements, fatigue, nausea, and low blood cell counts. Additionally, radiation may irritate the vagina, causing discomfort for female patients. In addition to short-term effects, the following long-term side effects may also occur:
- Damage to anal tissues from radiation can cause the anal sphincter to malfunction, leading to possible difficulties in bowel movements.
- Radiation to the pelvis can weaken bones, increasing the risk of pelvic or hip fractures.
- Radiation can damage the blood vessels that nourish the inner lining of the rectum, leading to chronic radiation proctitis.
How does Anal Cancer treatment affect sexual activity?
APR may lead to erectile problems in men, difficulty or absence of orgasm, and may also damage the nerves that control ejaculation, resulting in dry orgasms. For women, APR usually does not lead to a decrease in sexual function, but there may be pain during sexual intercourse. Additionally, radiation therapy can affect fertility in both men and women, reduce male sexual function, and cause vaginal dryness or even vaginal narrowing and shortening in women.
▣ The information on this website has been reviewed by the HEAL Medical Team and is regularly updated according to the most recent clinical evidence. All content is provided for general informational purposes only and should not replace professional medical advice. Please consult your doctor or another qualified healthcare professional for personalized medical guidance.
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