Rectosigmoid Cancer

Rectosigmoid cancer is a type of cancer that forms in the area where the colon meets the rectum, presenting unique challenges in treatment decisions that depend on the tumor’s exact location.

Table of contents

• What is Rectosigmoid Cancer?
• Understanding the Location and Its Importance
• Signs and Symptoms
• Risk Factors
• Diagnosis and Testing
• Treatment Approaches

What is Rectosigmoid Cancer?

Rectosigmoid cancer develops in the rectosigmoid region, which is the area where the last part of the colon (called the sigmoid colon) connects to the rectum. The rectum is the final several inches of the large intestine, ending at the anus. This type of cancer belongs to a broader group called colorectal cancer, which includes cancers that start in either the colon or the rectum.^[1]

Like other colorectal cancers, rectosigmoid cancer typically starts as small growths called polyps on the inner lining of the intestine. Over time—often taking about 10 years—some polyps can develop into cancer if not detected and removed.^[4][5]

Understanding the Location and Its Importance

The exact location of a tumor in the rectosigmoid area matters significantly when deciding on treatment. Doctors measure the distance from the tumor to the anal verge (the opening of the anus), typically considering tumors between 9 to 20 centimeters from this point as rectosigmoid cancers.^[1]

An important landmark that helps guide treatment decisions is the peritoneal reflection. This is a fold of tissue in the pelvis that marks a transition point in the anatomy. Research shows that tumors located below the peritoneal reflection may benefit more from treatment before surgery (called neoadjuvant therapy) rather than treatment after surgery.^[1]

The challenge with rectosigmoid cancer is that it sits in a transition zone. Doctors must carefully determine whether to treat it more like rectal cancer or more like sigmoid colon cancer, as the treatments for these two conditions differ.^[1]

Signs and Symptoms

Rectosigmoid cancer may not cause symptoms in its early stages. When symptoms do appear, they are often similar to other, less serious digestive problems. Common symptoms include:^[2][5]

• Blood in the stool, which may appear bright red or dark maroon
• Changes in bowel habits, such as diarrhea, constipation, or needing to pass stool more often
• A feeling that the bowel doesn’t empty completely after using the bathroom
• Narrow or thin stools
• Abdominal or belly pain with no clear cause
• Bloating or cramping in the stomach
• Unexplained weight loss
• Tiredness or weakness
• A lump in the rectum that may be felt during a medical examination

If you notice blood in your stool or persistent changes in your bathroom habits, it’s important to talk to a healthcare provider. While these symptoms don’t always mean cancer, they should be checked out.^[5]

Risk Factors

Several factors can increase the chance of developing rectosigmoid or colorectal cancer. Some of these can be changed, while others cannot.^[7]

Risk factors you cannot change:

• Age: The risk increases as you get older, with most cases diagnosed after age 50
• Family history: Having a parent, sibling, or child with colon or rectal cancer nearly doubles your risk
• Race: People who are Black have a higher risk compared to other racial groups
• Personal history of colorectal cancer, ovarian cancer, or large polyps
• Inherited genetic conditions such as familial adenomatous polyposis or Lynch syndrome

Risk factors you can change:

• Smoking cigarettes
• Drinking three or more alcoholic drinks per day
• Having obesity
• Not getting enough physical activity
• Eating a lot of red or processed meat

Medical conditions that increase risk:

• Having chronic ulcerative colitis or Crohn’s disease for 8 years or longer

Having one or more risk factors doesn’t mean you will definitely develop cancer. Many people with risk factors never get colorectal cancer, while some people with no known risk factors do develop it.^[7]

Diagnosis and Testing

Rectosigmoid cancer is often first suspected during routine screening tests or when symptoms prompt a visit to the doctor. Several tests help diagnose the condition and determine how far it has spread.^[10]

Colonoscopy: This is the main test used to look inside the colon and rectum. A doctor inserts a long, flexible tube with a camera through the anus to examine the entire colon. During this procedure, the doctor can take small tissue samples for testing.^[10]

Biopsy: Small pieces of tissue are removed during colonoscopy and examined under a microscope in a laboratory. This confirms whether cancer cells are present and provides information about the type of cancer.^[10]

Imaging tests: After cancer is diagnosed, additional scans help determine the cancer’s stage—meaning how large it is and whether it has spread. These may include CT scans, MRI scans, or ultrasound examinations of the pelvis.^[1][10]

Blood tests: These check your overall health and may include measurement of a substance called CEA (carcinoembryonic antigen), which can be elevated in some colorectal cancers.^[10]

Treatment Approaches

The treatment for rectosigmoid cancer depends on several factors, including the tumor’s exact location, its stage, and whether it has spread. The main treatments include surgery, radiation therapy, chemotherapy, and combinations of these approaches.^[1]

Surgery: The primary treatment is removing the cancerous tumor and surrounding tissue. The type of surgery depends on where exactly the tumor is located in the rectosigmoid area.^[1]

Neoadjuvant therapy: For tumors located below the peritoneal reflection—meaning closer to the rectum—treatment may begin with chemotherapy and radiation therapy before surgery. Research shows that 161 patients with advanced rectosigmoid cancers were studied, with 97 receiving treatment before surgery and 64 having surgery first. Patients with tumors below the peritoneal reflection who received treatment before surgery had better outcomes, with none experiencing cancer returning in the local area.^[1]

Adjuvant therapy: Treatment given after surgery, typically chemotherapy, may be recommended to kill any remaining cancer cells and reduce the risk of the cancer coming back.^[1]

Chemoradiotherapy: This involves combining chemotherapy and radiation therapy. It is often used for rectal cancers and may be recommended for rectosigmoid tumors depending on their location.^[13]

The decision about which treatment approach to use—and in what order—depends on careful evaluation of the tumor’s position. Doctors may use imaging studies to identify anatomic landmarks like the peritoneal reflection to guide these decisions.^[1]