You Need to Know the Types of Colorectal Cancer

Colorectal cancer is the name given to any cancer that develops in the colon (also known as the large intestine) or in the rectum. For both men and women, it is one of the deadliest and most common types of cancer.

The silver lining is that timely screening has a track record of detecting it early and saving lives.

Talk with your doctor about when you should start being screened. Knowing your family history can also help determine the right time, so be sure to research any history of colorectal cancer and share that information with your doctor. Also, consider making lifestyle changes that can help reduce your risk.

Like all cancers, colorectal cancer happens due to a wide array of factors, including your genes, environment and lifestyle. It's usually impossible to pin down one cause.

There is more than one type of colorectal cancer. Colon and rectal cancer are often grouped together since they are both part of the same organ/system and can share similar signs and symptoms. However, there are also many differences in how colon cancer and rectal cancer can manifest and spread, and in how they are treated. It's important to understand this distinction and know the differences between the conditions.

Colorectal cancer: overview and statistics

Colorectal cancer is the fourth-most common type of cancer in the United States, according to the National Cancer Institute's SEER data. About 151,000 Americans are diagnosed with colorectal cancer each year, which represents about 7.9 percent of all new cancer cases. Of those who have colorectal cancer, about 52,000 died in 2022, which accounts for about 8.6 percent of all U.S. cancer deaths.

Colorectal cancer is more common in males than females, with 43.4 new cases per 100,000 people per year among males of all races. Females develop the disease at a rate of 32.8 new cases per 100,000 people per year.

Another significant point in examining the statistics for colorectal cancer is that the rate is much higher among African American and Native American men, increasing to more than 52 cases per 100,000 people for both groups.

As an incentive to get screened, the five-year relative survival rate for people whose colorectal cancer is detected early, in the localized stage, is 91 percent. Overall, the five-year relative survival rate is just 65 percent, significantly lower than survival rates for many other forms of cancer. Once the disease gets past the localized stage, it is more difficult to treat.

The good news is these figures represent an increase in early diagnosis and major improvements that have been made in terms of screening techniques, education about the importance of getting screened and the ability of doctors to treat the disease.

"Many years ago, we didn't know a whole lot about colon cancer and we didn't really look for it or try to prevent it," said Shahrad Hakimian, M.D., a gastroenterologist with UCLA Health, part of the University of California, Los Angeles. "There was an increase in rates of colorectal cancer, but starting in the mid-1990s and then more in the early 2000s, we started looking for early signs of colorectal cancer a little bit more. And since that time, the incidence has started to decline."

What is the colon?

The colon is the distal part, or last portion, of the gastrointestinal tract. It's part of the large intestine, which also includes the rectum and the anus. It is responsible for receiving liquified food from the small intestine after most of the nutrients have already been absorbed.

The job of the large intestine is to take the remaining water and electrolytes from the remains of the food as its powerful muscle system moves it along toward the rectum and then the anus. At the same time, bacteria in the colon further break down the waste as it is dehydrated and turned into feces.

What is the rectum?

The rectum is the final part of the large intestine, the last six inches or so just before the anus.

Once the lower part of the colon sends the waste product that's left from the preceding digestive process to the rectum, what remains is indigestible material, dead cells shed by the lining of the intestine—the mucosa—as well as a bit of mucus and water.

If you eat 16 ounces of food, about 5 ounces of feces will be what's left after your body extracts everything it can use.

As the feces enter the rectum, you get the urge to defecate, which is just the continuation of the muscle contractions that have moved everything along from above.

Types of colorectal cancer

Colorectal cancer refers to any cancer that develops in the lower gastrointestinal system, including the colon and the rectum. Technically, people get colon cancer or they get rectal cancer, but they're frequently lumped together simply because both body parts are part of the same system and they're very closely related.

However, there are some important differences in how colon cancer and rectal cancer "work," what damage they can do and how they are treated.

"Colon cancer is basically like any other cancer," said Niket Sonpal, M.D., an internist and a gastroenterologist in New York City. "It develops inappropriately from a number of factors: genetics, diet, age. There are so many risk factors for colon cancer. So all of these things play a role."

Over time, the colon can develop abnormal outgrowths called polyps, Sonpal added. These are precancerous growths in the colon that are often immediately harmless when they are limited to the superficial layers of the colon and not rapidly growing. If they end up growing out of control, however, they become cancerous. If left untreated, this cancer can spread to other parts of the body even before you might notice any symptoms.

This is why it's so important to undergo any recommended screening that's appropriate for your age and background. For people of average risk, the American Cancer Society (ACS) recommends you talk to your doctor about regular screening starting at age 45.

While treating early-stage colon cancer can be straightforward, cancer of the rectum is a bit more complex because the function of the rectum involves coordination with the surrounding muscles that form the sphincter, which is critical in storing feces and to defecation. Treatments, including surgery, can impair this functionality. The typical way people defecate involves the powerful rectal muscles controlling the process. Without that musculature to hold it in until you're ready to defecate, life can get tricky.

"If [cancer] is in the rectum, it can be a little more complicated," Hakimian said. "It can affect the muscles near the anus, and some of the muscle may need to be removed. Then there are concerns for incontinence and things like that. If they can't save any of the muscle, then ostomy can be a consideration."

Understanding colorectal cancer

It's important to understand how common colorectal cancer is and how it works. Don't ignore your primary care doctor or the gastroenterologist, whose message is going to be that you should understand how preventable it is and how vital it is to get screened. This is especially true for people at high risk, including those with a family history of the disease or those in the higher-risk demographic groups, including Black and Native American men.

If you're 45 or older and have never been screened, talk to your healthcare provider. A colonoscopy is a simple, painless procedure that looks for polyps. The doctor can literally snip precancerous polyps out before they develop into something more serious.

Better that than facing a 65 percent five-year survival rate or the prospect of losing a chunk of your colon or rectum in the future.