Colorectal Cancer Diagnosis and Treatment

Dr. Mayo and registered nurse Rachel Shafer together greet a patient at the South Waterfront clinic.
Dr. Skye Mayo (left), with registered nurse, Rachel Schafer (middle), is one of our expert surgeons for cancers of the digestive system.

Diagnosis and treatment at the OHSU Knight Cancer Institute offer you the best chance of an excellent outcome. You’ll receive care from a team of experts with the latest techniques. We offer you: 

  • Highly trained doctors and other providers who focus on treating gastrointestinal cancers.
  • Advanced surgical techniques, including minimally invasive methods and those that preserve your function. 
  • The latest treatments, such as one-dose radiation therapy during surgery and chemotherapy for cancer that has spread to the liver.
  • Team-based care, with specialists gathering in a weekly tumor board meeting to combine their expertise patient by patient.
  • Exceptional nursing care, with nurses who arrange appointments and provide expert ostomy care.
  • Research and clinical trials that put us on the leading edge of care.

Diagnosing colorectal cancer

Common tests include:

A drawing shows a section of colon with two small clumps of abnormal tissue inside called polyps. Left untreated, polyps in the colon can turn into cancer.
Polyps, abnormal growths inside the colon, can become cancer if left untreated.
  • Colonoscopy: A thin, flexible tube tipped with a light and camera is inserted into the rectum and colon to check for cancer or abnormal growths called polyps. Polyps can become cancer.
  • Stool tests: A stool sample is checked for blood, a possible sign of cancer.
  • Blood tests: A blood sample is checked for signs of cancer such as a protein produced by colorectal cancers. 

Read more about colorectal cancer screening on our Understanding Colorectal Cancer page. If doctors find abnormalities, tests may include:

  • A biopsy, in which a tissue sample is checked under a microscope for cancer cells.
  • Molecular testing at Knight Diagnostic Laboratories to determine the cancer’s genetic makeup so it can be matched with the most effective treatments. 
  • Magnetic resonance imaging, or MRI, which uses radio waves and magnets to create precise pictures.

Treatments for colorectal cancer

Your care may include more than one type of treatment. Your care team will work with you to develop a plan for your unique needs. 


Our highly skilled surgeons use advanced techniques to remove colorectal cancer. They are also experts in saving important nerves and tissues linked to sexual function and to bowel and bladder control.

For early-stage cancers, surgery may be the only treatment you need. We use minimally invasive surgery when possible. Sometimes we use an endoscope, a long, flexible instrument with a camera, light and tools. Or we may use laparoscopic surgery, which involves small incisions and tiny instruments. This results in less pain and faster recovery. It also spares nearby healthy tissue.

Procedures include:

  • Endoscopic mucosal resection (EMR): Liquid is injected under a polyp to separate it from the surface. The surgeon can then remove it without taking out a segment of your colon or rectum.
  • Endoscopic submucosal dissection (ESD): Your surgeon removes cancers just below the surface by carefully cutting the top tissue layers.
  • Transanal endoscopic microsurgery (TEM): The surgeon removes precancerous rectal lesions and early tumors through the anus. This technique spares the sphincter and anus as well as nerves linked to sexual function and bladder control.

We also offer advanced treatments such as:

  • Colectomy: The surgical team removes a section of your colon, and then reconnects your digestive tract. (See below.) 
  • Transanal total mesorectal excision, or TME: This combines laparoscopic and endoscopic techniques to remove difficult-to-reach rectal cancers. The cancer and surrounding rectal tissue are removed. The colon or remaining rectum is reconnected to the anus, if possible.
  • Sphincter-preserving surgery: This uses sophisticated techniques to remove cancers while preserving your ability to control your bowels. 
Medical illustration of resection of the rectum with anastomosis (portion of rectum is removed and the remainder is reattached to the colon)
This illustration shows the surgical removal of rectal cancer and how the colon and anus are rejoined in a procedure called anastomosis.

If a section of your colon or rectum is removed, your surgical team will provide one of these:

  • Anastomosis: This reattaches your remaining colon or rectum, restoring your large intestine and function. You may need several surgeries, with healing time in between, and a temporary colostomy or ileostomy. 
  • Colostomy: This surgery creates an opening in the belly called a stoma and attaches it to your colon. A pouch outside your body collects stool. At OHSU, you’ll find nurses with special training to help you with all aspects of ostomy care. You can still take part in any activity.
  • Ileostomy: This is similar to a colostomy. Your surgeon connects the lowest part of your small intestine, called the ileum, to the opening in your belly.


We use the latest medications and approaches to slow or kill cancer cells. For more advanced colon cancer, we may recommend chemotherapy after surgery to prevent the disease from returning. Most often, chemotherapy is given in an IV drip. We also offer advanced techniques, such as:

  • Hepatic arterial infusionThis treatment is for colorectal cancer that has spread to the liver. We implant a small pump under the skin to deliver chemotherapy directly to the liver.
  • HIPEC surgery: This technique can benefit patients with advanced colorectal cancer. Surgeons remove tumors, then deliver a powerful dose of chemotherapy directly inside the abdomen.

Targeted therapy

We use advanced testing to identify genetic “targets” in your tumor. Medications can match the target, like a key fitting into a lock, to attack the cancer cell.

The Knight Cancer Institute is a pioneer in this approach, which kills cancer cells while leaving healthy cells mostly alone.

For colorectal cancers, targeted medications are given by IV or pill to:

  • Keep tumors from forming new blood vessels, pinching off their nutrient supply.
  • Attack a protein that cancer cells need to grow.
  • Block signals that tell a cancer cell to grow or form blood vessels.

Radiation therapy

Radiation therapy uses energy beams to destroy cancer cells. We are regional leaders in image-guided radiation therapy, or IGRT. We’re also the only center in Oregon to offer radiation therapy in one dose during surgery.

We use radiation therapy mainly for rectal cancer. We may recommend it for colon cancer when surgery isn’t possible or to relieve symptoms of late-stage disease.

You may have radiation therapy:

  • Before surgery: This can shrink the cancer so it’s easier to remove.
  • During surgery: Intraoperative radiation therapy, or IORT, delivers one dose directly to the surgical site. Our Mobetron device uses less radiation and spares more healthy tissue, resulting in fewer side effects. 
  • After surgery: This can kill any remaining cancer cells to keep cancer from spreading or coming back. 
  • With chemotherapy: Combined chemoradiation may replace surgery.
  • For late-stage cancers: Radiation therapy can relieve pain, including when disease has spread to nearby organs such as the liver. Stereotactic body radiation therapy enables us to safely deliver a high dose to targeted areas.


Immunotherapy harnesses your body’s immune system to fight cancer. One approach targets a genetic trait in some advanced cancers to make them more visible to the immune system.

Medications called “checkpoint inhibitors” stop these cancers from sending signals that hide them from the immune system. The immune system then recognizes the cancer as a threat and goes on the attack.

Additional services

We offer many services to help you and your family, including: 

  • Cancer rehabilitation services: Our rehabilitation specialists have expertise in helping cancer patients manage side effects of cancer and treatment.
  • Palliative care: Our expert Palliative Care Service can help you and your family manage symptoms and anxiety. Our providers offer expertise in cancer, and services are available at any stage.
  • Young adults: OHSU offers Oregon’s only program for people ages 15 to 39 diagnosed with cancer.
  • Clinical trials: Leading clinical trials, which may offer you access to new treatments before they’re widely available.
  • Colorectal cancer registry: OHSU cancer registries, including one for colorectal cancer, offers the chance to help advance our research and learn about the latest findings.
  • Genetic testing and counseling: Our expert medical geneticists can help you identify your risk of colorectal cancers linked to hereditary syndromes, which are passed down in families.
  • Cancer dietitians: Dietitians with expertise in cancer can help you manage nutritional needs before, during and after treatment.
  • Cancer social workers: Social workers with cancer training can help you overcome barriers to care, such as transportation, housing and financial issues. 

Learn more

For patients

Call 503-494-7999 to:

  • Request an appointment
  • Seek a second opinion
  • Ask questions


Knight Cancer Institute, South Waterfront

Center for Health & Healing, Building 2
3485 S. Bond Ave.
Portland, OR 97239

Free parking for patients and visitors

Refer a patient

Cancer clinical trials

Clinical trials allow patients to try a new test or treatment.

Read more