About Anal Cancer
Anal cancer is a type of cancer that originates in the cells and tissues of the skin lining either inside or outside the anus. The anus is the body’s opening through which stool is expelled. Located below the rectum, it represents the final segment of the gastrointestinal tract.
Although anal cancer is close to the rectum, it is distinct from rectal cancer in both disease characteristics and treatment. Anal cancer is primarily classified according to the cell type where it originates, with squamous cell carcinoma (SCC) being the most common type, accounting for about 90% of cases. Other types of anal cancer include adenocarcinoma, melanoma, basal cell carcinoma, and neuroendocrine tumours. Treatment will vary based on the type of anal cancer.
Anal Cancer Symptoms
Overlapping symptoms with colorectal cancer include:
Changes in bowel habits, such as:
Both types of cancer can be diagnosed at a regular colonoscopy exam. Anal cancer is typically treated with radiation and chemotherapy given together, while colorectal cancer treatment will vary depending on the location of the tumour.
Diagnosis
Understanding your diagnosis can help you feel more informed and confident as you work with your healthcare team during your treatment journey.
What is squamous cell carcinoma?
Squamous cell carcinoma is a type of cancer that starts in squamous cells, which are thin, flat cells that line many parts of the body. These cells are found on the surface of the skin and inside organs and body cavities, including the anus, mouth, and lungs.
When squamous cells grow out of control, they can form a tumour. In anal cancer, this happens in the lining of the anal canal. This is known as squamous cell carcinoma of the anal canal (SCAC).
How SCAC May Be Described
Localized or Locally Advanced SCAC
This means the cancer is still in the area where it started. It may involve nearby tissues or nearby lymph nodes, but it has not spread to distant parts of the body.
Locally Recurrent or Metastatic SCAC
This means the cancer has come back after treatment.
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Locally recurrent means it has returned in the same area or nearby.
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Metastatic means it has spread to other parts of the body.
Newly Diagnosed Metastatic SCAC
This means the cancer has already spread beyond the anal canal at the time of diagnosis.
In Remission
Remission means that no signs of cancer are found after treatment. Even in remission, your healthcare team will continue follow-up care because there is still a chance the cancer could return.
What treatment may involve
At this stage, treatment usually includes chemoradiation therapy (CRT) or, in some cases, surgery.
Chemoradiation therapy (CRT) combines chemotherapy and radiation therapy at the same time. The goal is to shrink the tumour, destroy cancer cells, and reduce the chance of the cancer spreading.
What you may experience during treatment
CRT usually takes 5 to 6 weeks to complete.
Common side effects may include:
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Skin irritation or tenderness in the treatment area
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Nausea or vomiting
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Mouth sores
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Soreness or irritation in the anus
Your healthcare team can suggest ways to help prevent or manage side effects, so be sure to talk with them about any symptoms you notice.
Follow-up after treatment
About 8 to 12 weeks after treatment, your doctor will usually schedule a follow-up exam to see how well the treatment worked. This may include:
Metastatic SCAC
Metastatic SCAC means the cancer has spread to other parts of the body, such as the liver or lungs. This is also called late-stage or stage IV SCAC.
How treatment is managed
Treatment often includes drug therapy, such as chemotherapy. Newer approved treatment options are also available, and your healthcare team will discuss which approach is best for you based on your situation.
Treatment
Treatment for anal cancer depends on the stage of the disease, the tumour type, and a person’s overall health. Most anal cancers are treated with a combination of chemotherapy and radiation therapy, with surgery used in specific situations.
For most stage I-III anal cancers, the standard first treatment is combined chemotherapy and radiation, often referred to as the Nigro Protocol. This approach uses radiation therapy together with the chemotherapy drugs 5-fluorouracil (5-FU) and mitomycin-C. This combined treatment is highly effective and, in many cases, can eliminate the cancer without the need for surgery.
Surgery may be recommended if cancer remains after chemoradiation, if the cancer returns, or in certain early or advanced cases where other treatments are not suitable.
Additional treatment options are also emerging, particularly for people with recurrent or metastatic anal cancer. Immunotherapy works by helping the body’s immune system recognize and attack cancer cells more precisely than traditional chemotherapy.
Immunotherapy drugs such as nivolumab (Opdivo) and pembrolizumab (Keytruda) are approved by Health Canada for the treatment of metastatic or recurrent anal squamous cell carcinoma (SCC). Clinical trials are currently exploring the used of these drugs in earlier lines of treatment in non-metastatic settings.
Retifanlimab (Zynyz) is another immunotherapy that is approved for the treatment of advanced or metastatic anal squamous cell carcinoma in certain settings. It is currently undergoing reimbursement review in Canada.
Patients with advanced or recurrent anal cancer may wish to speak with their healthcare team about whether participation in a clinical trial is an option.
Anal Cancer Resources
Sources:
Links to relevant clinical trials
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