Colon and Rectum Cancer | Cancer


Colon and Rectum Cancer

UC Davis Comprehensive Cancer Center leads the region in the treatment of complex and advanced colon and rectum cancers. We use the latest therapies to fight cancer and give you the best possible quality of life.

Medically reviewed by Ankit Sirin, M.D. on Sep. 25, 2023.

Patient and provider talking in clinic room

Personalized Cancer Care for You

Our oncologists and surgeons at UC Davis Comprehensive Cancer Center specialize in colorectal cancers at all stages, including early cancers as well as cancers that have spread (metastasized) to other parts of your body.

We are almost always able to offer surgery that is minimally invasive (done with small incisions and advanced technology rather than a big cut). Whenever possible, we treat cancer without the need for a temporary or permanent colostomy (opening in your abdomen to remove waste from your body). We focus on your unique needs and quality of life.


What Is Colon and Rectum Cancer?

Colon and rectum cancers develop in the lining of your large intestine, which is part of your lower gastrointestinal (GI) tract. If you think of your intestine as a long tunnel, your stomach connects to the small intestine, which connects to the large intestine, also called the colon. Your rectum is between your colon and anus. Both your colon and rectum absorb water and help move food waste out of your body.

Colon and rectum cancer (sometimes called colorectal cancer) usually starts as a polyp. A polyp is a benign (noncancerous) growth. Polyps that aren’t removed can turn into cancer.

Our experts treat the most common form of colorectal cancer, adenocarcinoma, as well as uncommon tumors such as:

  • Colorectal lymphoma
  • Gastrointestinal neuroendocrine tumors
  • Gastrointestinal stromal tumors
  • Small-cell colon carcinoma

Colon and Rectum Cancer Symptoms

Symptoms of colorectal polyps or cancer are often similar to those of other, less serious conditions. Talk to your physician as soon as you suspect that something is wrong.

Common Symptoms

Colorectal cancer symptoms may include:

  • Abdominal pain or bloating
  • Blood in your stool
  • Changes in bowel habits
  • Diarrhea or constipation
  • Fatigue
  • Nausea and vomiting
  • Unexplained weight loss

Emergency Symptoms

Seek immediate medication attention if you have:

  • Abdominal swelling
  • Difficulty having a bowel movement or passing gas
  • Heavy rectal bleeding
  • Repeated vomiting or vomit that contains blood
  • Severe or sharp abdominal pain

Colon and Rectum Cancer Causes and Risk Factors

Colorectal cancer occurs when cells multiply uncontrollably and form tumors. Research shows that changes (mutations) in certain genes that regulate cell growth and division can lead to cancer.

Some people are born with abnormal genes, but most develop genetic mutations during their lifetime. Experts don’t know exactly why or how this happens. Certain factors, however, increase the risk of colorectal cancer.


Most colorectal cancers occur in people in their 60s and 70s, though colorectal cancer in young adults is on the rise. Colorectal cancer is now the top cause of cancer death in people under 50.

Researchers are looking into the reasons for this trend. Lifestyle factors (obesity and lack of exercise) may play a role.


You are more likely to develop colorectal cancer if you are overweight or obese and don’t exercise. Drinking alcohol, smoking or eating a diet high in red meats or processed meats can also increase your risk.

Personal and Family Medical History

Your risk of colorectal cancer increases if you or a close relative has had colorectal polyps. You’re also more likely to develop colorectal cancer if you have inflammatory bowel disease (Crohn’s disease or ulcerative colitis) that goes untreated.

Some diseases passed down in families (inherited syndromes) may make colorectal cancer more likely. Talk to your physician to learn more about your risk.  


Colon and Rectum Cancer Screening and Diagnosis

Colorectal cancer is more likely than other cancers to spread early in the disease. It can spread to the liver, lungs, brain or lymph nodes. That’s why it’s important to detect, diagnose and treat colorectal cancer as soon as possible.

At UC Davis Comprehensive Cancer Center, our experienced teams use the latest screening and diagnostic techniques to deliver accurate results and the best possible outcomes. Oncologists, colorectal surgeons, gastroenterologists, radiologists and pathologists work together to ensure you receive the right tests for your needs and risk level.

Screening tests for colorectal cancer may include:

Stool tests

We may analyze a sample of your stool to check for blood or changes to DNA. At-home stool test kits are available. Talk to your physician about your risk level and whether at-home testing is right for you.


A sigmoidoscopy is similar to a colonoscopy, but it’s slightly less invasive. The test uses an endoscope to examine only the lower part of your colon. You don’t need sedation for a sigmoidoscopy.

CT colonoscopy (virtual colonoscopy)

This test uses CT scans to create detailed images of your colon and rectum. Since it's noninvasive and doesn’t use an endoscope, we may recommend it for those who can’t have sedation for a traditional colonoscopy.


A colonoscopy is the most common screening and diagnostic test for colorectal polyps and cancer. Your specialist uses an endoscope (flexible tube with a light and video camera on one end) to examine your entire colon and rectum. You're typically asleep (sedated) during a colonoscopy.

Diagnostic tests for colorectal cancer may include:

Blood tests

We use the latest blood tests to detect substances in your blood that could indicate cancer (biomarkers). A carcinoembryonic antigen assay checks for high levels of certain proteins in your blood. We also do tests to check your blood for circulating DNA fragments released by tumors.

Transrectal ultrasound

A transrectal ultrasound is a quick test to examine the rectum, take tissue samples for biopsy and stage rectum cancer. Staging means finding out how much cancer is in your body, and where it is. We insert a small probe (device about the size of a finger) into your rectum. Sound waves from the probe produce detailed images of your rectum on a computer screen.

Other imaging exams

We may do an MRI or PET scan of other areas of your body to find out if cancer has spread from your colon to your liver, lungs, brain or lymph nodes (clusters of cells that are part of your body’s immune system).


This test is the only way to confirm a colorectal cancer diagnosis. During a colonoscopy or sigmoidoscopy, we take a small tissue sample from your tumor or polyp. A pathologist examines the sample under a microscope to check for signs of cancer.

Rectum and Colon Cancer Treatments at UC Davis Health

UC Davis Comprehensive Cancer Center is home to the region’s leading colorectal cancer specialists. Our expertise and innovative therapies mean we can offer innovative care for both early cancer as well as complex and advanced cancers, even if you’ve been told that you’re out of treatment options.

We also participate in ongoing clinical trials, which give those who are eligible access to tests and treatments not available elsewhere. Our state-of-the-art colon and rectum cancer treatments include:

Colorectal Cancer Surgery

Surgery is the most common treatment for colorectal cancers. Our skilled specialists typically remove polyps or cancer using procedures called resections.

We can almost always remove early-stage cancers and polyps with endoscopic or laparoscopic/robotic techniques. These procedures are minimally invasive (no large incisions in your abdomen), so you recover faster and with less pain.

Whenever possible, we try to avoid a permanent ostomy if we need to remove part or all of your rectum or colon. If you do need a temporary ostomy, our surgeons have extensive experience in ostomy reversal after you’ve healed from your initial surgery.

Colonic Stenting

We implant a stent (hollow, mesh tube) in your colon to open areas of your bowel blocked by tumors. A stent can delay the need for immediate emergency colorectal surgery and allow you to have a planned operation laparoscopically/ robotically without need for an ostomy.

Radiofrequency Ablation

We may use radiofrequency ablation to treat small tumors that have spread to your liver from your colon or rectum. During this minimally invasive procedure, we use a needle to deliver an electric current directly to the tumor. Heat from the current kills cancer cells.

Sphincter-Sparing Colorectal Surgery

When possible, we remove tumors and diseased tissue while leaving anal sphincter muscles intact. These muscles help you have bowel movements. UC Davis Comprehensive Cancer Center is among only a few programs in Northern California to offer sphincter-sparing colorectal surgery.

Transanal Techniques

We have the ability to use multiple transanal techniques, including transanal endoscopic microsurgery (TEM), transanal minimally invasive surgery (TAMIS) and robotic TAMIS to remove rectal tumors through your anus. This minimally invasive technique is an alternative to major abdominal surgery that can be used to treat some tumors.

Radiation Therapy

Radiation therapy uses high-energy radiation to destroy tumors. We may use radiation therapy before surgery to shrink tumors (neoadjuvant therapy), making them easier to remove. Used after surgery, radiation can destroy any remaining cancer cells (adjuvant therapy).

Radiation therapy is especially common for rectum cancer treatment because this cancer is more likely to return in the same location. Our radiation oncologists often recommend chemoradiation (a combination of radiation and chemotherapy) before surgery to reduce the risk of reoccurrence. It can also reduce the need for a permanent colostomy.


Chemotherapy uses drugs to destroy cancer cells. You may receive chemotherapy before or after surgery for colorectal cancer. If you aren’t a candidate for surgery due to your age, health or stage of cancer, chemotherapy is an alternative treatment.

Transarterial Chemoembolization

We may recommend transarterial chemoembolization (a type of chemotherapy) if colorectal cancer has spread to your liver. In this procedure, we insert a catheter into the main artery supplying blood to your liver to deliver strong doses of chemotherapeutic drugs directly to liver tumors. The drugs also work to partially block the artery, so tumors do not receive the blood they need to grow.

Targeted Therapy

Targeted therapy works on specific proteins and genes in different types of tumors. These drugs target the parts of cancer cells that allow them to grow and divide. We may recommend targeted therapy for colorectal cancer in combination with other treatments.

Learn more about UC Davis Comprehensive Cancer Center

Preventing Colon and Rectum Cancer

A healthy lifestyle and regular colorectal cancer screenings may reduce your risk of developing cancer. If precancerous colorectal polyps do develop, early detection and removal can prevent cancer. If cancer develops, screening helps us diagnose and treat it as quickly as possible.

Colorectal cancer screening is recommended for adults between the ages of 45 and 75. Your physician may recommend earlier screening if you have risk factors.

While methods for colorectal cancer screening can vary, minimally invasive exams and stool tests are the most common types for detecting colorectal cancer early. A colonoscopy is the best way to spot precancerous colorectal polyps early, before they turn into cancer.

How many new cases?

32 in 100KPeople in the U.S. diagnosed with colon and rectum cancer in 2020

Source: Centers for Disease Control and Prevention (CDC): United States Cancer Statistics: Data Visualizations

Request an Appointment

Our cancer specialists provide thorough evaluations and personalized treatment plans. Learn more about how to make an appointment at UC Davis Comprehensive Cancer Center.



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