Anal cancer and colorectal cancer both start in the lower gastrointestinal tract, but these types of cancer differ in many ways.
We spoke to a gastrointestinal radiation oncologist Dr. Emma Hollidaylearn more about the differences between anal and colorectal cancer.
Which parts of the lower digestive system do anal and colorectal cancers affect?
Anal cancer affects the anal canal and anus.
Colorectal cancer affects the large intestine, including the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, and rectum.
What are the risk factors for anal and colorectal cancer?
The most common cause of anal cancer is the human papillomavirus (HPV), specifically types 16 and 18, which causes 90% of anal cancers and precancers.
Other less common risk factors for anal cancer include:
- HIV infection
- smoking
- A weakened immune system caused by an organ transplant, an autoimmune disease, or drugs taken for other conditions
You are at increased risk of colorectal cancer if:
Other risk factors for colorectal cancer include:
What are the symptoms of anal and colorectal cancer?
Several symptoms overlap. Both anal and colorectal cancer can cause:
- weakness or fatigue
- Unexplained weight loss
- abdominal or pelvic pain
- Changes in bowel habits, such as:
- bleeding from the anus or rectum
- constipation
- diarrhea
- emergency bowel movements
- Difficulty controlling bowel movements
Symptoms specific to anal cancer include:
- Itching and pain around the anus
- a lump in or around the anus
- pain in the anus when defecating
Symptoms specific to colorectal cancer include:
- abdominal pain
- bloating
- Feeling that the bowels are not completely empty
Anal and colorectal cancer often have symptoms that can be mistaken for other diseases. For example, anal cancer is often misdiagnosed as hemorrhoids. This is why regular cancer screenings are so important. If your symptoms don’t improve after a few weeks, be sure to get a colonoscopy or get a second opinion.
How is anal and colorectal cancer diagnosed?
Anal and colorectal cancers can be diagnosed with routine colonoscopies even before patients develop symptoms.
If you develop symptoms during your screening colonoscopy, a diagnostic colonoscopy can be performed to look inside your anal canal, rectum, and colon to check for cancer. A biopsy can be performed to determine if cancer is present.
How is anal and colorectal cancer treated?
The most common type of cancer cell that causes anal cancer is squamous cell carcinoma. The disease responds well and is most commonly treated with a combination of radiation therapy and chemotherapy. A procedure called local excision may be used to remove very small early anal cancers that have not spread to the lymph nodes or invaded the sphincter muscles. This represents a minority of cases of anal cancer.
Treatment options for colorectal cancer depend on where the cancer starts. Colon tumors can be treated with surgery alone or with chemotherapy before or after surgery, depending on the size of the tumor and whether the cancer has spread to lymph nodes.
Because rectal tumors are more likely to recur after surgery, rectal cancer is often treated with chemotherapy and/or radiation therapy before surgery. People with rectal cancer have several treatment options, depending on the location of the tumor in the rectum, its size, and whether the cancer has spread to the lymph nodes. These treatment options include:
- Surgery is performed after chemotherapy, and radiation is not given if the tumor has shrunk sufficiently after chemotherapy.
- Chemotherapy and radiation therapy follow, and if no cancer remains after chemotherapy and radiation therapy, surgery is not done.
- Chemotherapy, radiation therapy, or surgery if the risk of recurrence is high
Getting the correct diagnosis is the best way to get the right treatment. Additionally, if detected early, both anal and colorectal cancers can be successfully treated.
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