Precise Radiation for Colorectal Cancer

Colorectal cancer will affect approximately 5% of Americans, men and women alike. Found early, there is a 90% chance for a cure. Treating it typically requires surgery, followed by radiation therapy to destroy any remaining cancer cells. However, older radiation delivery methods can expose nearby, healthy tissue to damage.

Cutting-edge therapies, such as Intensity Modulated Radiation Therapy (IMRT) and Image-Guided Radiation Therapy (IGRT) enable physicians to deliver higher doses of precisely focused radiation to cancerous tumors while sparing nearby healthy tissue. This is particularly significant as treatment for colorectal cancer since damage to surrounding tissue can cause extremely unpleasant side effects, primarily related to bowel and bladder function.

What Is Colorectal Cancer?

Colorectal cancer is a term used to refer to cancer that starts in either the colon or the rectum (the last five inches of the colon). Often, it starts as a polyp—a slow growth of tissue that begins in the lining and grows into the center of the colon or rectum. A polyp may be benign (not cancerous) or may become malignant (cancerous). Removing a polyp early may prevent it from becoming cancerous.

Over 95% of colon and rectal cancers are adenocarcinomas that begin in the cells that line the inside of the colon and rectum. The other 5% of tumors are much rarer.

Who Gets Colorectal Cancer?

Not counting skin cancer, colorectal cancer is the third most common cancer in the United States. The American Cancer Society estimates there are approximately 106,000 new cases of colon cancer and 40,800 new cases of rectal cancer diagnosed each year. Personal risk of developing colorectal cancer is about 1 in 19.

Death rates from colorectal cancer have been declining for the past 15 years, primarily due to early detection and treatment. Thanks to colorectal screening, polyps can be found and removed before they turn into cancer and cancer can be found earlier when it is easier to cure. Treatments have also improved dramatically.

The majority of colorectal tumors are found in patients over age 50. Other risk factors include:

  • personal or family history of colon cancer, particularly younger than age 60.
  • history of polyps in the colon, ulcerative colitis or Crohn’s Disease.
  • ethnicity; for reasons not understood, African Americans and Ashkenazi Jews have higher risk.
  • lifestyle choices such as diets high in fat and red meats and low in fruits and vegetables; lack of exercise; overweight; smoking and alcohol consumption.

How Do I Know If I Have Colorectal Cancer?

The size of the colorectal cancer and how far it has spread are the best indicators for survival. Therefore, early detection is key.  Beginning at age 50, the American Cancer Society recommends the following screening guidelines for both men and women without significant risk factors or symptoms:

  • a yearly fecal occult blood test to check stool for blood.
  • every five years a double-contrast barium enema where the area is examined with an intensive x-ray to look for abnormalities.
  • every 10 years, a colonoscopy where the doctor uses a long, lighted tube (called a “colonoscope”) to look inside the rectum and the entire colon for polyps or other abnormal areas that may be cancerous.

People who have any of the colorectal cancer risk should consult with a physician about more frequent screening.

Often there are no obvious signs of colorectal cancer, but some symptoms can include:

  • change in bowel frequency, such as alternating episodes of diarrhea and constipation.
  • bloody bowel movements or rectal bleeding.
  • general abdominal discomfort.
  • unexplained weight loss.
  • chronic fatigue.
  • bloating.
  • unexplained anemia.

There are several tests physicians can use to further the diagnostic process and look for colorectal cancer. In addition to the screening tests described above, these include:

  • Digital rectal exam (DRE), to evaluate the rectum for abnormal tissues.
  • Sigmoidoscopy, a procedure in which the physician uses a thin, lighted tube to look inside the rectum and lower portion of the colon (called the sigmoid) for polyps or other abnormalities.
  • Colonoscopy, which is performed like the sigmoidoscopy, but allows the physician to see the entire colon.
  • CT, MRI or PET scan, to determine if the cancer has spread.

As with other cancers, the only way to know for sure is with a biopsy—a procedure in which a sample of the tumor is sent to the lab to be examined under a microscope. This sample is typically taken during the sigmoidoscopy or colonoscopy.

What Are My Treatment Options?

Physicians use the results of diagnostic tests to determine the site of the cancer and to stage it—or tell how far it has spread. This helps determine the outlook for recovery and the best course of treatment. Patients should work together with their physician to choose among several treatment options that may be used alone or in combination, and to understand the risks and benefits of each.


Surgery is the primary treatment for colorectal cancer, particularly in the early stages. For cancers that have not spread, surgery alone may provide a cure. Depending on the location and stage of the cancer, chemotherapy or radiation therapy may be used before surgery to shrink the tumor, or after surgery to kill any remaining cancer cells. Colorectal surgery can be performed in different ways:

  • Colonoscopy – small malignant polyps may be removed from the colon or upper rectum with the aid of a small, thin tube called a “colonoscope.” Some small tumors in the lower rectum can be removed through the anus without a colonoscope.
  • Laparoscopy – early colon cancer may be removed with the aid of a thin, lighted tube called a “laparoscope.” Three or four tiny cuts are made into the abdomen and the laparoscope is inserted to see inside. Long, thin surgical instruments are used to remove the tumor and part of the healthy colon. Nearby lymph nodes also may be removed. The remaining intestine and liver are checked to see if the cancer has spread.
  • Open surgery – the surgeon makes a large cut into the abdomen to remove the tumor and part of the healthy colon or rectum. Some nearby lymph nodes are also removed. The surgeon checks the rest of your intestine and the liver to see if the cancer has spread.
    • Colectomy – with this procedure, the two open ends of the colon are re-connected.
    • Colostomy – if the two ends of the colon cannot be reconnected, a small hole is made in the abdominal wall and waste is passed through this hole to a plastic bag outside the body.


Chemotherapy (also called “chemo”) employs oral or injected drugs to kill cancer cells. These drugs enter the bloodstream and travel throughout the body, making the treatment useful for cancers that have spread to distant organs. For colorectal cancer, chemotherapy is typically used to shrink rectal tumors before surgery. After surgery chemo may increase the survival rate for patients with some stages of cancer. While it is not typically indicated for advanced or recurrent colorectal cancer, it can help relieve symptoms.

Because chemo kills some normal cells in addition to malignant ones, it can cause side effects that vary depending on the type of drug used. These include, but are not limited to, fatigue, nausea, vomiting, loss of appetite, hair loss, mouth sores, changes in menstrual cycle and infertility. It can also cause low white blood cell and platelet counts resulting in higher risk of infection and easy bruising/bleeding. Chemotherapy is often used concurrently with radiation therapy.

Targeted Therapy

Researchers are learning more about the gene changes in cells that cause cancer, enabling them to develop new drugs that specifically target these changes. These drugs work differently than standard chemotherapy drugs, usually with less severe side effects. Man-made proteins called monoclonal antibodies have been approved for use, along with chemo, against colorectal cancer.

Radiation Therapy

Radiation that kills or shrinks tumors may be used alone or in combination with other treatments. It is often used to shrink tumors before surgery, which may spare the anal sphincter and prevent the need for a colostomy.  It is also used after surgery to kill any remaining cancer cells and reduce the chance of the cancer returning. For rectal cancer, radiation is usually given with chemotherapy. However, due to the sensitive nature of this area, unpleasant side effects of radiation therapy can include more frequent bowel movements, diarrhea, abdominal cramping, pressure or discomfort in the rectal area, more frequent urination, burning with urination, skin irritation, nausea and fatigue.

Brachytherapy With brachytherapy, radioactive seeds (pellets) are placed next to, or directly into, the cancer. The seeds give off small amounts of radiation over several weeks. This method is sometimes used in treating people with rectal cancer, particularly sick or older people who would not be able to withstand surgery. It carries small risks associated with seed migration within the body.

3-D Conformal External-Beam Radiation Therapy Three-dimensional conformal radiation therapy is an innovative high-technology radiation technique. Computer simulation produces an accurate image of a tumor and surrounding organs so that multiple radiation beams can be shaped exactly to the treatment area. These precisely focused beams allow nearby normal tissue to be spared.

Intensity Modulated Radiation Therapy (IMRT) and Image-Guided Radiation Therapy (IGRT)

IMRT/IGRT are rapidly replacing traditional radiation therapy for treating certain cancers. These methods deliver higher radiation doses more precisely to cancerous tumors while avoiding healthy tissue. For colorectal cancer, this type of radiation therapy may prevent some unpleasant side effects. IMRT/IGRT can also potentially shorten the duration of therapy and enable physicians to treat some colorectal cancers for which traditional radiation therapy was not an option.

 Your Colorectal Cancer Treatment Partner

At Rainier Cancer Center, we offer patients a variety of treatment options, from traditional radiation to cutting-edge therapies such as IMRT and IGRT that may not be widely available in other treatment centers. Regardless of the treatment path, we pride ourselves on providing each patient with the best outpatient experience in the most comfortable atmosphere. Treating colorectal cancer can be a complicated process, so our personal Cancer Navigators help guide each patient through their journey.

IMRT & IGRT: Fighting Colorectal Cancer with Precision

Quick and painless, external-beam radiation has long been used to destroy cancer cells. The latest methods—Intensity Modulated Radiation Therapy (IMRT) and Image-Guided Radiation Therapy (IGRT)—provide the most advanced technology for fighting cancer. Used alone or together, these therapies allow higher doses of radiation to be delivered with greater precision and accuracy without destroying surrounding, healthy tissue. For colorectal cancers this precision may reduce the incidence of side effects such as frequent bowel movements, diarrhea, abdominal cramping, pressure or discomfort in the rectal area, more frequent urination and burning with urination.

For patients, IMRT/IGRT means:

  • more effective treatment focused on cancer cells.
  • less radiation exposure to normal tissue.
  • potentially fewer and milder side effects.
  • treatment for some tumors that couldn’t previously be treated by radiation.

How IMRT Works

IMRT is a specialized radiation therapy that uses powerful treatment planning software to calculate precise beam angles, shapes and exposure times tailored to each tumor. The radiation beam can be broken up into many smaller beams and the intensity of each small beam can be adjusted individually. This may allow a higher dose of radiation to be delivered to the tumor with less risk to nearby healthy tissue, potentially decreasing the duration of treatment and increasing the chance of a cure.

How IGRT Works

Tumors can move during a course of treatment. IGRT combines imaging and treatment capabilities on a single machine. This way, tumors can be tracked between, as well as during, treatments, allowing radiation to be focused more precisely. Images captured before each radiation session are compared to previous sessions so that clinicians know the exact location of the tumor each time. IGRT software also accounts for breathing and motion during treatment, ensuring the radiation stays focused on the tumor.

3D Conformal Radiation Therapy

When IMRT/IGRT is not an option, Century Cancer Centers can also provide traditional radiation therapy to colorectal cancer patients. Like a regular x-ray, radiation beams are focused on the affected area from outside the body. It can be used alone or in combination with other cancer therapies.

What to Expect During Treatment

The treatment process is similar for IMRT, IGRT and traditional 3-D conformal radiation therapy.

First, we’ll schedule an appointment with a radiation oncologist. During this visit, we’ll perform a simulation of the treatment. You will be positioned on the treatment machine the same way you will be for actual treatment. The radiation oncologist will determine the need to use an immobilization device (such as a cast, mold or headrest) to keep you in the same position during treatment. Then, we’ll take a CT scan to precisely map your anatomy. Using information from the CT scan, the radiation therapist will mark the area(s) to be treated, either on your skin or on the immobilization device. Simulation sessions take 30 to 60 minutes and may be repeated at intervals throughout your course of treatment.

Next, your radiation oncologist and treatment team will design a treatment plan tailored to you. They will use information from the simulation session, anatomical maps obtained from the CT scan, previous medical tests and, in many cases, sophisticated treatment planning software.

For colorectal cancer, radiation therapy is typically administered 5 days per week for 5 to 6 weeks. However, your treatment team will determine the best course of treatment for you. During each session, positioning takes from 5 to 15 minutes. Actual treatment time lasts about 10 minutes and is painless. The radiation is delivered using a machine called a “linear accelerator” which generates x-rays or photon radiation. The linear accelerator moves so that patients can lie comfortably without being re-positioned during treatment.

The treatment room is spacious, and you will not be completely enclosed by equipment. A radiation therapist will position you to ensure successful treatment then go to an adjoining control room. From there, he or she will monitor you closely during radiation treatment using video cameras. The therapist can hear you at all times, and the treatment can be immediately discontinued if you feel uncomfortable or ill. If IMRT/IGRT are employed, the therapist may move the machine or treatment table during treatment to best target the exact area of the tumor. Once each treatment is complete, you can return to your normal daily activities as tolerated.

A follow up exam with your radiation oncologist will be scheduled after your last treatment to discuss side effects. From there, physicians will determine the proper course of ongoing treatment.