Rectal Cancer

Rectal cancer is a cancer that forms on the inner lining of your rectum. Your rectum is the last several inches of your large intestine. This cancer typically grows very slowly.

Most rectal cancers start as clumps of abnormal cells (polyps) known as adenomas. It can take 10 to 15 years for a polyp in your rectum to turn into a cancerous tumor.

Regular colonoscopies and other screening tests may detect polyps before they become cancerous tumors. Surgery to remove small cancerous tumors may cure it.

Symptoms of rectal cancer

Rectal cancer may not cause symptoms right away. You may not have symptoms until a tumor in your rectum grows large enough to affect your rectum or how you poop. The growing tumor may cause symptoms like:

• Rectal bleeding
• Bright red or dark red blood in your poop (stool)
• Constipation or diarrhea
• Feeling like your bowels aren’t empty after you poop
• Very narrow poop, meaning it’s about as big around as a pencil
• Belly pain
• Cramping and gas
• Fatigue
• Unexplained weight loss

Rectal cancer causes

The exact cause is unknown. But some risk factors increase the chance you’ll have it, including:

• Age: Like most cancers, your risk increases with age. The average age of diagnosis is 63. But research shows a growing number of people aged 50 and younger are being diagnosed with rectal cancer.
• Biological family history: Your chance increases if a close family member has colon cancer or rectal cancer.
• Certain health issues: Having inflammatory bowel disease, like Crohn’s disease or ulcerative colitis, may increase your risk. So can having obesity.
• Lifestyle: Smoking and eating a lot of red meat and processed meat may increase your risk.
• Inherited disorders: Lynch syndrome, familial adenomatous polyposis (FAP), MUTYH‐associated polyposis (MAP) and hamartomatous polyposis syndromes are examples of inherited disorders that may increase your risk.
• Sex: Males are slightly more likely to develop it.
• Race: Statistically, people who are Black are more likely to have this disease. Experts aren’t sure why that’s the case.

How doctors diagnose rectal cancer

A healthcare provider will ask about your symptoms and your health history. They’ll do the following tests:

• Digital rectal exam
• Colonoscopy
• Biopsy

Your provider may refer you to an oncologist for more tests. Your oncologists may do blood and imaging tests. They may also do a follow-up colonoscopy, proctoscopy and/or sigmoidoscopy.

Blood tests

Your oncologist may order the following blood tests to look for signs of rectal cancer:

• Complete blood count (CBC) to check your red blood cell levels (low levels may be a sign of bleeding in your rectum)
• Comprehensive metabolic panel (CMP), which shows how well your kidneys and liver work
• Liver enzyme test to check for issues with your liver
• CEA test to measure the blood protein carcinoembryonic antigen (high levels may be a sign of rectal cancer)

Imaging tests

Your oncologist may do these tests to check for signs that cancer has spread outside of your rectum:

• CT scan
• MRI scan
• Ultrasound

Your oncologist will use test results to establish the cancer stage. There are five rectal cancer stages:

• Stage 0: There are cancerous cells on the surface of the tissue that lines your rectum.
• Stage I (1): The cells form a tumor that grows below the tissue that lines your rectum. There may be cancer in your rectal wall.
• Stage II (2): The tumor is in your rectal wall. It may be in tissues around your rectum.
• Stage III (3): The tumor invades lymph nodes next to your rectum and some tissues outside of your rectal wall.
• Stage IV (4): It spreads to more lymph nodes and organs, like your liver or kidneys.

How is rectal cancer treated?

Surgery to remove cancerous tumors is one of the most common rectal cancer treatments. There are different procedures:

• Transanal endoscopic microsurgery (TEMS): This is an option if you have a small tumor that hasn’t spread. Your provider inserts a small scope into your anus so they can reach your rectum and remove the tumor.
• Low anterior resection (LAR): You may have this procedure if there’s a large tumor. This procedure removes all or part of your rectum.
• Abdominoperineal resection (APR): With this procedure, your surgeon removes your anus, rectum and part of your colon. They’ll also do a colostomy so waste can leave your body.
• Multivisceral resection: This is surgery for cancer that’s spread to nearby organs or structures. It involves removing the organs and structures.

Other rectal cancer treatments are:

• Chemotherapy, which uses anticancer medication to kill cancerous cells
• Radiation therapy to target cancerous tumors
• Targeted therapy, which involves medication that targets specific genetic changes in cancerous cells
• Immunotherapy, which helps your immune system fight cancer

When should I see my healthcare provider?

You’ll have regular follow-up tests after you finish treatment. Your appointments may follow this timeline and include tests like:

• Molecular residual disease tests: These tests check for circulating tumor DNA (ctDNA). This is a DNA fragment from the tumor cell that circulates in your blood. You may first have this test a month after your treatment. Your provider may repeat the test over the next few years.
• Colonoscopy: You’ll have a colonoscopy a year after your treatment. If tests don’t find signs of cancer, you’ll have another in three years. If those tests don’t find rectal cancer, you’ll have a colonoscopy every five years.
• Proctoscopy: If you had a TEMS procedure, you​ may have a proctoscopy every three to six months for the first two to three years after your surgery. 
• CEA tests: You may have CEA blood tests every three to six months for the first two years after treatment. You’ll have fewer tests after that. You may have one every six months for the next three to five years.
• CT scans: You may have a scan every six months to once a year if your provider thinks the cancer may come back.

What are the survival rates for rectal cancer?

The American Cancer Society reports on five-year relative survival rates for many kinds of cancer, including rectal cancer. A five-year survival rate compares survival of people with the same type and stage of cancer with people who don’t have cancer.

For example, the overall five-year relative survival rate for rectal cancer is 67%. That means people with rectal cancer are about 67% as likely to be alive five years after diagnosis as people who don’t have cancer. The society groups cancer survival rates by tumor location at diagnosis instead of cancer stage. The five-year relative survival rates for rectal cancer are:

• Local: 90% — this refers to cancer that hasn’t spread outside your rectum.
• Regional: 74% — in this case, there’s cancer in nearby lymph nodes or the lining of your abdomen (belly).
• Distant: 18%— cancer in your rectum has spread to your bones, liver, lungs or other more distant areas of your body.

When should I start rectal cancer screening?

In general, people age 45 and older should have regular screening tests for rectal cancer, among other types of early-onset cancer. But everyone’s situation is different. Your medical history and family medical history may increase your risk. That’s why it’s a good idea to ask a healthcare provider about screening tests.

Colonoscopy is the most common screening test, but there are also other options:

• Fecal occult blood test (FOBT): This test detects hidden blood in your poop. Medical pathologists test samples of your poop for blood that you may not see just by looking.
• Guaiac-based fecal occult blood test (gFOBT): Like the FOBT, this test looks for blood in poop that you may not notice.
• Fecal DNA test: This test looks for signs of genetic changes and blood in your poop.
• Sigmoidoscopy: This test lets healthcare providers examine the inside of your lower colon (sigmoid) and colon.