Important research into anal cancer is now under way in many hospitals, medical centers, and other institutions around the world. Each year, scientists find out more about what causes the disease, how to prevent it, and how to improve treatment.
Causes and prevention
Research has identified the human papilloma virus (HPV) as a major cause of anal cancer. Researchers are learning how HPV affects molecules inside anal cells to cause them to become cancerous.
Improved understanding of the molecular changes inside anal cancer cells is expected to help scientists develop new drugs to fight this disease.
Ongoing research is being done on the value of screening tests for anal cancer, especially in people with major risk factors. The test studied most is anal cytology, sometimes called the anal Pap test. This test may be useful in early diagnosis of anal cancer and pre-cancer (called anal intraepithelial neoplasia, or AIN). In this test, cells are gently scraped from the lining layer of the anus and checked under a microscope. Some doctors already recommend this test for people at high risk for anal cancers, such as those who are HIV positive.
Research is also in progress on treating AIN to help prevent cancer from developing.
Anal cancer is not common, so it’s often hard to get enough people in clinical trials to study new treatments. Still, doctors are looking to improve on current treatments and develop new ones to help people with anal cancer.
In the past several years, studies have shown the benefits of combining radiation with chemotherapy. This approach has reduced the number of surgical procedures needed for anal cancer, including the need for permanent colostomies.
New radiosensitizing agents – chemotherapy and other drugs that increase the effect of radiation therapy – are being studied in clinical trials. Combining these treatments might allow people to get lower doses of radiation and chemotherapy, which could lessen the possible side effects.
Doctors are learning more about how to give external radiation more accurately and effectively to decrease the effects on normal healthy tissues. Other research is being done to learn about the possible benefits of combining external radiation and internal radiation therapy.
Doctors are also studying ways to improve surgery and its side effects. For instance, studies are now looking at implanting an artificial bowel sphincter in people who have an extensive type of surgery known as abdominoperineal resection (APR). The hope is that this artificial sphincter might allow people to avoid the need for a permanent colostomy. Currently such treatment is only available in carefully monitored clinical trials.
Chemotherapy (along with radiation) is an effective treatment for many anal cancers, but the drugs that are used can cause serious side effects in some people. Doctors are studying whether giving more or less chemo to certain people might help treat these cancers while limiting the side effects. Newer chemo drugs are also being studied.
As researchers have learned more about the changes inside cells that cause them to become cancer, they have developed newer drugs that specifically target these changes. Targeted drugs are different from standard chemotherapy drugs. They sometimes work when standard chemo drugs don’t, and they often have different (and less severe) side effects.
For example, many anal cancers have too much of a protein called EGFR on their cells, which helps the cells grow. Some drugs that target EGFR, such as cetuximab (Erbitux®) and panitumumab (Vectibix®), are already used to treat other types of cancer, and are now being studied for use with chemoradiation in treating anal cancer.
Immunotherapy is treatment that boosts the body’s immune response against cancer cells. Different kinds of immunotherapy are being study for use against anal cancer.
Treatment vaccines: The HPV vaccines available at this time help prevent HPV infection, but they do not treat infections already present. Researchers are now working on vaccines to treat women and men who already have HPV infections, by causing their body’s immune system cells to attack the HPV-infected cells.
Another goal of this research is to help the immune system attack pre-cancers and even cancers that contain HPV. An experimental vaccine has shown promise so far in treating pre-cancers of the vulva, and is now being studied against anal pre-cancer (AIN).
Another HPV-based vaccine is being studied for use in combination with chemoradiation to treat anal cancer.
Imiquimod cream: Studies are also looking at using imiquimod cream to treat anal intraepithelial neoplasia (AIN). It is applied to the problem area 3 times a week. Imiquimod is approved as a treatment for anal and genital warts. It acts by boosting the body’s immune response. It has been used “off-label” to treat AIN in HIV-positive men with good results, and more recently was shown to be helpful in a clinical trial.
Tumor-infiltrating lymphocytes: Advanced anal cancers are hard to treat. In one treatment now being studied for these cancers, a piece of a tumor is surgically removed. The white blood cells in the sample that are attacking the tumor (known as tumor-infiltrating lymphocytes) are grown in the lab and then given back to the patient to treat the remaining cancer. A drug known as interleukin-2 (IL-2) is given along with the immune cells, which helps the cells stay alive and kill tumors. This approach is still in the very early phases of study.
Last Revised: 01/20/2016