Right-sided colon cancer may cause different symptoms than left-sided colon cancer. The first sign of right-sided colon cancer is often anemia caused by bleeding.

Colon cancer is one of the most common cancers diagnosed in the United States. It can develop anywhere along your colon, which comprises three parts:

  • Ascending colon: This is the first part of your colon that attaches to your small intestine. It moves stool upward.
  • Transverse colon: This is the middle part of your colon where stool moves laterally through your intestines.
  • Descending colon: This is the final part of your colon that moves stool downward until reaching your rectum and anus, where it then leaves your body.

The right side of your colon contains the ascending colon and two-thirds of the transverse colon.

Read on to learn about how right-sided colon cancer differs from cancer that develops on the left side.

Illustration showing potential locations of right- and left-sided colon cancerShare on Pinterest
Potential locations of right- and left-sided colon cancer. Illustration by Wenzdai Figueroa

Like many types of cancer, colon cancer often doesn’t cause symptoms in the early stages until the tumor grows large or spreads.

When symptoms do develop, they may include:

The most common place colon cancer is detected is in the descending colon.

Left-sided colon cancers occur more frequently than right-sided cancers.

This may be because left-sided tumors are easier to detect during a colonoscopy.

However, in recent years, researchers have found a shift toward more right-sided colon cancer diagnoses, largely due to better early detection techniques.

This right side of your bowel is wider than the left side, so tumors may grow larger before causing symptoms. The first sign of these cancers is often anemia from chronic blood loss.

Symptoms of anemia include:

Right-sided tumors that spread to distant locations tend to spread to the tissue that lines your abdomen and pelvis.

Early symptoms of right-sided colon cancer

In a 2023 study from Morocco, researchers reported the following as the most common symptoms in 99 people with right-sided colon cancer:

  • diarrhea
  • symptoms related to bowel obstruction
  • constipation

In a 2017 study from Pakistan, researchers reported that symptoms related to bowel obstruction were the most common initial symptoms in 20 people with right-sided cancer.

In 85 people with left-sided cancer, rectal bleeding was a more common initial symptom.

Is right-sided colon cancer worse than left-sided colon cancer?

Right-sided colon cancer tends to be more advanced and larger when it’s diagnosed. Many studies have found that right-sided colon cancer is associated with a poorer outlook, but some studies have found the opposite.

Colonoscopy misses about 2–6% of cases of colon cancer, and most of these occur on the right side. Delayed diagnosis can mean the cancer grows larger before it’s detected.

Hereditary cancer syndromes, except for familial adenomatous polyposis, tend to occur on the right side. Lynch syndrome is the most common hereditary cause of colon cancer.

People who carry a gene mutation associated with Lynch syndrome have more than an 80% chance of developing colon cancer by age 44 years.

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In the 2023 study from Morocco mentioned above, researchers found that the most common symptoms of left-sided colon cancer were:

  • bowel obstruction
  • rectal bleeding

Rectal bleeding was the most common left-sided colon cancer symptom in the aforementioned 2017 study from Pakistan.

When left-sided colon cancer spreads, it tends to spread to the liver or lungs.

Doctors often use 5-year relative survival rates to measure cancer survival. This statistic looks at how many people with a cancer are alive 5 years later than people without the cancer.

Here’s a look at the 5-year relative survival rates of colon cancer by stage in the United States from 2013–2019:

Stage5-year relative survival rate
Localized91%
Regional73%
Distant13%
All stages63%

Research on whether people with right-sided colon cancer have worse survival has been mixed. Some studies suggest early stage cancer on the right side may have a better outlook, and late stage cancer on the left may have a better outlook.

The research

In a 2021 study from researchers in Germany and the United States, no difference in survival was found between left- and right-sided colon cancer among 417 people with varying stages of disease.

In a 2022 study from China, researchers found the side of colon cancer did not influence survival, but right-sided cancer was associated with a quicker time to cancer reoccurrence after treatment in people with stage 2 cancer.

Another study from China found that people with stage 2 cancer had a better outlook when their cancer occurred on the right side.

In a 2021 study from Spain, researchers found that more than 50.8% of people with right-sided cancer developed complications after surgery compared with only 26.1% of people with left-sided disease.

Of those with right-sided disease, 80.4% were alive 12 months later compared with 90.5% of people with left-sided disease.

Other factors influencing survival

Factors associated with a better outlook for people with colon cancer include:

  • earlier cancer stage
  • lower cancer grade
  • no signs of cancer along the edges of surgically removed tissue (positive margins)
  • no growth into lymph or blood vessels
  • lower levels of carcinoembryonic antigen (CEA)
  • no bowel obstruction or perforation
  • not having mucinous adenocarcinoma, signet ring cell carcinoma, or small cell carcinoma
  • tumors with a DNA change called microsatellite instability (MSI), which mostly occurs in right-side tumors
  • not having KRAS or BRAF gene mutations

Research suggests that right- and left-sided colon cancers may have different initial symptoms. The first sign of right-sided cancer seems to be anemia caused by blood loss.

It’s unclear whether right-sided colon cancer is associated with a poorer outlook. Some research suggests that early stage cancers on the right side may have a better outlook but late stage cancers on the left side may have a better outlook.