Medically reviewed by Douglas Rubinson, MD, PhD
Anal cancer is a type of cancer that forms in tissues of the anus. The anus is the opening of the rectum to the outside of the body and at the end of the gastrointestinal tract.
What is the leading theory on why the incidence rate has risen in anal cancer?
Despite its increase in frequency, anal cancer is an uncommon cancer affecting around 8,000 patients in the US each year. It is not clear what is leading to the increase in anal cancer incidence.
Smoking, lack of HPV vaccination, immunosuppression, HIV/AIDS, and exposure to HPV through sex all contribute to HPV risk.
How does anal cancer relate to HPV?
Nearly all (>90%) cases of anal cancer are related to HPV infection. Anal cancer, like cervical cancer, is largely preventable with vaccination against HPV in adolescence.
What are the symptoms of anal cancer?
The most common symptoms of anal cancer include:
- bleeding from the anus often exacerbated with bowel movements
- and the sensation of a growth or a mass.
These symptoms can all be present in common benign conditions such as hemorrhoids. It is important that patients with persistent and bothersome symptoms be evaluated by their doctor.
Many patients with anal cancer have lengthy delays in diagnosis due to hesitation to see their doctor and assumption that their symptoms are just hemorrhoids and do not need to be evaluated.
Who is at risk of developing anal cancer?
Anal cancer can occur in anyone. The most common age at diagnosis is the early 60s.
There are some people who are at higher risk for anal cancer. Patients with chronically suppressed immune systems such as related to immunosuppressive medication or infection with HIV/AIDS are at higher risk. Doctors often recommend that anyone diagnosed with anal cancer be tested for HIV.
Both anal cancer and cervical cancer are associated with HPV viral infections. Any woman with anal cancer should have an up-to-date pap smear to make sure that the same virus that caused their anal cancer is not causing an abnormal pap smear or cervical cancer.
What is the difference between anal cancer and colon cancer?
Despite their proximity, anal cancer is a very different cancer than rectal cancer. The cells that line the anus are squamous cells (similar to the cells of the skin, cervix, mouth and esophagus), and anal cancer is a type of squamous cell carcinoma.
In contrast, the cells lining the rectum, the last part of the large intestine before the anus, form adenocarcinomas (gland-forming cancers). Anal cancers are associated with HPV-infection, while rectal adenocarcinomas are not.
Generally, what does treatment for anal cancer entail?
Historically, anal cancer was treated with surgery. However, 40 years ago, a trial was performed in which patients received chemotherapy and radiation prior to surgery. When the patients surgical resections were analyzed by pathologists, they saw that there was no living cancer remaining. One patient had refused surgery and was cured with chemotherapy and radiation alone.
As a result of this trial, the standard of care for anal cancer that has not metastasized to another organ is to treat with radiation therapy combined with chemotherapy. Radiation is given five days a week for six weeks. Chemotherapy is given intravenously in the first and fifth weeks of radiation.
After completion of chemoradiation, scans and exams are performed to be certain that the cancer has been eliminated. Most patients with localized anal cancer are cured with chemotherapy and radiation.
For patients whose cancer is not eliminated with chemotherapy and radiation, or returns to the anus, a surgeon will usually attempt to remove the recurrent disease.
For patients with metastatic disease to another organ either at diagnosis or recurrent after treatment, treatment is usually provided with either chemotherapy or immunotherapy.
Is there anything else people should know about anal cancer/having anal cancer?
Anal cancer is highly curable disease. Because early disease is symptomatic, it has the chance to be identified early when the chance of cure can be more than 90%. Delays in diagnosis, allowing for spread to lymph nodes or other organs, can reduce or eliminate a chance to be cured.
Anyone with bothersome and persistent anal symptoms should be evaluated by their doctor rather than assume their symptom is “just a hemorrhoid.”