What Is Rectal Cancer?

Colorectal cancer is the third-most-common cancer affecting both men and women in the U.S. While colon and rectal cancer are often grouped together, these are actually two distinct types of cancers. Colon cancer often gets more attention, but rectal cancer makes up 30% of all colorectal cancers. 

And while cancer of the rectum and colon do share some similarities, treatment differs between the two. Below, we will review some of the important differences between rectal and colon cancer and provide an overview of what you need to know about rectal cancer. 

What is the difference between rectal cancer and colon cancer?

The primary difference between colon and rectal cancer is the location of the cancer. And the terminology can be a little confusing, too. 

The colon and rectum make up the large intestine, which is the last part of the gastrointestinal system. When food travels through the colon, water and nutrients are absorbed, and fecal matter (stool) is left over to exit the body. The rectum stores the stool until it is ready to be expelled. And then, the anus acts as an exit valve and opening to the outside of the body. The rectum is approximately 5 to 6 inches long and connects to the anus.

The treatment for rectal cancer is also different from the treatment for colon cancer. Treatment for rectal cancer often involves some combination of radiation, chemotherapy, and surgery. When the cancer is located in the rectum, the surgical technique to remove it is different than for other locations of the large intestine. For example, some early rectal cancers can be removed directly through the anus because the rectum is so close to the anal opening. In contrast, all colon cancers require abdominal surgery for removal unless they are confined to a polyp that can be removed with a colonoscopy. The specific location of the cancer matters, because it directs the treatment and also the response of the cancer to this treatment.

Who is at risk for rectal cancer?

Many of the risk factors for rectal cancer are similar to those for colon cancer. People at higher risk of rectal cancer include those who:

• Smoke cigarettes.

• Drink a large amount of alcohol. 

• Eat a diet low in fiber or high in red meat.

• Are not physically active.

• Are classified with a BMI over 30.

• Have a history of colon or rectal polyps.

• Have a history of colorectal cancer.

• Have a history of certain genetic conditions that predispose them to cancer, including Lynch syndrome or familial adenomatous polyposis (FAP).

• Have a history of inflammatory bowel disease. 

• Have a family history of colon or rectal cancer in their parents, siblings, or children. 

Studies also show that rectal cancer affects more men than women. And people with certain ethnic and racial backgrounds are also at higher risk, including Black Americans. 

Most guidelines recommend that people begin colorectal cancer screening at age 45. But people at higher risk may need to start screening earlier. It’s a good idea to discuss your risk factors with a healthcare provider. Together, you can decide on the best age to begin screening for colorectal cancer. 

Screening for rectal cancer

Both colon and rectal cancers are often found on screening tests. And the screening methods are similar for both. These include:

• Stool tests: These are quick tests that check for microscopic amounts of blood or certain DNA markers in the stool.

• Procedures: These look directly at the large intestine using a long, flexible tube that has a camera on one end. They include colonoscopy and sigmoidoscopy.

• Imaging: A virtual colonoscopy uses a CT scan to look for signs of cancer in the large intestine. 

Screening should start at age 45 for people of average risk. Those at higher risk, though, should start at a younger age. If you have risk factors for colon or rectal cancer, your provider can help you figure out the exact age you should start screening. 

What are the symptoms of rectal cancer?

Sometimes, rectal cancers do not lead to noticeable symptoms in the earliest stages. When symptoms do start to develop, the most common ones include:

• Change in bowel habits, like new onset of constipation or diarrhea.

• Stool that’s narrow in shape. This can occur if the tumor narrows the diameter of the rectum.

• Blood in the stool.

• Pain in the abdomen, pelvis, or rectum.

• Unexplained weight loss.

Many of these symptoms are not specific to rectal cancer and have much more likely explanations. For example, rectal bleeding can also happen with hemorrhoids, which are fairly common. And constipation is a very common condition that can happen for many different reasons. So, if you are experiencing these symptoms, don’t let your mind jump immediately to a cancer diagnosis. Talk to your provider about your concerns. 

When should I see a doctor if I’m having symptoms of rectal cancer?

It’s a good idea to mention your symptoms to a healthcare provider if they’re new or causing you any worry. They can help you figure out the cause and help you figure out if cancer screening is necessary. This is particularly true for if you have new symptoms and: 

• Risk factors for rectal cancer.

• They are persistent or worsening.

• You are unsure of the reasons for your symptoms. For instance, if you have been diagnosed with hemorrhoids as the cause of your bleeding, this may be less concerning than if you are having bleeding of unknown cause.

Is rectal cancer curable?

Rectal cancer is curable. And the prognosis largely depends on how deep the cancer has penetrated into the rectum and whether it has spread to other organs. Lower stages and less-advanced cancers having a better chance of cure. Though even certain higher-stage rectal cancers can be cured.

A treatment course for rectal cancer depends on how far the cancer has progressed and may include:

• Radiation therapy using X-rays directed at the cancer cells to shrink the tumor. This is usually performed before surgical removal.

• Chemotherapy using medicines that kill the cancer cells. This can be given before and/or after surgery. 

• Surgery that directly removes the entire rectum. Sometimes, surgical treatment for rectal cancer may involve a colostomy or ileostomy. This is when a portion of the rectum is removed and the remaining intestine is connected directly to the abdominal wall. This may be temporary or even avoidable depending on the stage of the cancer. 

Why trust our experts?

Written by:

Joanna Jan, MD

Joanna Jan, MD, is board-certified in internal medicine and licensed to practice medicine in the state of Pennsylvania. In 2017, she received her board certification from the American Board of Internal Medicine.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

Reviewed by:

Sarah Koller, MD, MS, FACS

Sarah Koller, MD, MS, is board-certified in general surgery and colorectal surgery. She is currently on faculty at the University of Southern California as an assistant professor of surgery.

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