Anal, Rectal and Colon Cancer: What Are the Differences? 

A Keck Medicine of USC colorectal surgeon discusses symptoms and treatments for colon, rectal and anal cancers. 

More younger adults are being diagnosed with colon and rectal cancers.  

“This has been a steady trend over the last few decades,” says Joongho Shin, MD, a colorectal surgeon with the USC Colorectal Surgery Program, part of Keck Medicine of USC. He treats patients at Keck Hospital of USC and at Keck Medicine locations in Buena Park, Bakersfield and Koreatown. 

Unfortunately, many younger adults — and even some health care providers — tend not to consider that people in their twenties and thirties might get colon or rectal cancers and might need screening tests such as colonoscopies. Raising awareness around these cancers has become increasingly important. 

“Not only patients but also their providers need to be more tuned in to the possibility that their symptoms could be signs of colon or rectal cancer,” Dr. Shin says. 

Here, Dr. Shin discusses the possible symptoms, as well as the diagnoses and treatments, for colon, rectal and anal cancers. 

The differences between colon, rectal and anal cancers 

Both colon and rectal cancers are adenocarcinomas, which begin in the glands lining organs such as the large intestine. Anal cancer, meanwhile, is a squamous cell carcinoma that starts in the lining of the anal canal.  

Rectal cancer occurs in the rectum, which is the 12 to 15 centimeters of the large intestine above the anal canal. Colon cancer affects the remaining five feet of the large intestine. Anal cancer develops in the anus, the short canal at the end of the rectum. 

Don’t ignore the warning signs 

Consult your physician if you have blood in your stool or persistent changes in your bowel habits, which might be signs of colon cancer. With rectal cancer, symptoms can include not only bleeding and bowel-habit changes but also a greater urgency to go to the bathroom. 

Even if they don’t have GI symptoms, individuals with a family history of colon or rectal cancer should get a colonoscopy starting at age 45 or earlier. And if someone in your immediate family had colon or rectal cancer before the age of 50, start getting colonoscopies 10 years before the age that your family member’s cancer was diagnosed. 

If a biopsy confirms the presence of colon or rectal cancer, then a blood test, CT scan and potentially an MRI will help determine how advanced the cancer is. The patient should then be referred to a colorectal specialist. 

Unfortunately, there is no screening test for anal cancer. So, consult your doctor if you have anal pain, anal bleeding or blood in your stool. 

Too often, Dr. Shin notes, the symptoms of colon, anal and especially rectal cancers get attributed to hemorrhoids — delaying diagnosis and treatment.  

“The main thing is to not ignore the warning signs,” he says. 

Colon, rectal and anal cancers: Mostly treatable 

Most colon, rectal and anal cancers are very curable. Colon cancer is treated mainly with surgery or potentially surgery with chemotherapy. Treatment for rectal cancer is more complex and can involve chemotherapy, radiation and surgery. And among patients with anal cancer, almost 90% are cured with chemotherapy and radiation. 

If diagnosed early enough, colon or rectal cancer can be removed endoscopically, without having to take out part of the colon or rectum. “Early detection is the key,” Dr. Shin says. 

But more invasive colon and rectal cancers can be cured as well, though they likely require surgical removal of a portion of the colon or rectum. “Colon and rectal cancer is highly curable, even in advanced stages,” Dr. Shin says. 

Life after surgery 

If several inches of the colon are removed in patients with colon cancer, the procedure doesn’t really affect the frequency or pattern of their bowel movements.  

But if the same amount is removed from the rectum, which stores stool, the surgery does impact bowel habits. So it’s desirable for people with rectal cancer to avoid surgery if deemed appropriate by physician. Up to 40% of patients with rectal cancer do not have any evidence of cancer after receiving a specific protocol of chemotherapy and radiation, without surgery. 

Among patients with anal cancer, the roughly 10% who do not have a complete response after chemotherapy and radiation need surgery. If the surgery has to remove the anus or sphincter muscle, these patients need a colostomy, which is an opening for stool to pass from the large intestine through the abdomen into a special device. 

While Dr. Shin acknowledges that a colostomy is a life-changing experience, he emphasizes that people with stomas can lead normal, active lives. 

How to improve your colon, rectal and anal health 

• Engage in regular exercise. An active lifestyle can help prevent cancer — and can help people who have had cancer become less likely to have a recurrence. 

• Avoid eating processed meats. While there’s not a definitive link between certain foods and colorectal cancers, it’s clear that processed animal fat, such as bacon, ham and sausage, is a risk factor for colorectal and other cancers. 

• Take vitamin D supplements. It has not been shown clinically that vitamin D prevents colorectal cancer, but people who have colon or rectal cancer tend to have a greater vitamin D deficiency than people without these cancers. 

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Novid Parsi

Novid Parsi is a freelance writer for Keck Medicine of USC.

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