Rectal Cancer Rates Are Rising in Young Adults, and Nobody Knows Why
It is said that colon and rectal cancer was rare in the 1800’s, before massive industrialization in the United States occurred in the 20th Century. Now colon and rectal cancer, sometimes lumped together as “colorectal cancer” is the third leading cause of death in the United States. In 2009 there was approximately 17,000 deaths from rectal cancer and over 100,000 cases are diagnosed each year.
Recently an article in the American Cancer Society’s Journal Cancer discovered that rates of rectal cancer are rising in adults under the age of 40. Between 1984 and 2005 rates of rectal cancer have increased by approximately 80%. Though rectal cancer rates are relatively low in this age group, the rise is nonetheless concerning, especially as researchers are uncertain if the increase is due to increased diagnosis or a real increase in the number of cases of this disease. Given that young adults rarely get a colonoscopy to screen for rectal and colon cancer, many researchers have concluded that the rise is real.
Experts are recommending that young adults who present with bleeding from their rectum, which can be caused by cancer or more benign hemorrhoids, that these adults get a colonoscopy which will definitively rule out colon and rectal cancer. Everyone in the United States is recommended to get a colonoscopy by the age of 50 at the latest; people with a certain family history of colon cancer may need a colonoscopy performed at an early age.
But what would explain the rise in rectal cancer rates in young adults?
Rectal cancer is believed to be caused by a number of factors. Some are the so-called “genetic predispositions” which a given person is born with and increases the risk of developing rectal cancer. Others, called “environmental factors” include things such as diet and even exposure to cancer causing chemicals called carcinogens. If rectal cancer rates are truly rising at a rate of 3.8% a year, as the article in the journal Cancer suggests, then most likely this is due to a change in how we live our lives as Americans or the presence of something new in the environment.
Is an increasingly unhealthy American diet responsible for the increased rates of rectal cancer in young adults?
A diet high in saturated fats from animals and even certain vegetable oils, such as corn oil, is associated with an increased risk of colon and rectal cancer. Conversely, a diet which is high in fiber is believed to protect against colon cancer. Certainly the American diet has changed since the early 1980s, and increased amounts of saturated fats and decreased amounts of fiber are being consumed.
Could Americans unhealthy diet be increasing the risk of rectal cancer?
In addition to an unhealthy diet, drinking alcohol, such as drinking more than 32 oz. of beer, increases the risk of colon and rectal cancer, as does smoking, obesity, an a diet high in red meats and low in vegetables. However, colon cancer rates have remained steady over the past twenty years in the under 40 age group, while rectal cancer rates have skyrocketed in this age group and older groups as well. Perhaps rectal cancer risk is increased by dietary changes in a manner different from colon cancer.
However, a sexually transmitted virus can cause a certain type of anal cancer, may bear some similarities to rectal cancer. This virus, called the Human Papilloma Virus, or HPV, can cause anal cancer. HPV virus strains 16, 18, 31, 33 and 35 are associated with an increased risk of anal cancer and cervical cancer. In fact, 90% of all cases of anal cancer are caused by HPV. However, the changes in anal cancer are different from those usually seen in rectal cancer, which means that some doctors doubt whether HPV is the culprit.
Nonetheless, HPV has been linked to an “adenocarcinoma” of the cervix, a rare type of cancer. And rectal cancer is mostly of the adenocarcinoma cellular type. Could the increased rates of rectal cancer be due to HPV? More research will likely be needed to answer this question. The anus and rectum are relatively close anatomically, and HPV could easily enter the rectum and infect the cells lining this body cavity.
For now the rise in rectal cancers is unexplained and doctors are urged to consider this diagnose in younger patients.