How We Screen and Diagnose Colorectal Cancer

Diagnosing Colorectal Cancer
A timely and accurate detection of colorectal cancer is essential to planning the best course of treatment. In addition to a routine physical examination and blood tests, City of Hope doctors may also use the following tests to diagnose colorectal cancer:

  • Colonoscopy: Using a flexible, thin lit tube, a physician will examine the rectum and entire colon for cancerous changes. In addition to detecting colorectal cancer, colonoscopy also allows the doctor to extract and remove suspicious and precancerous tissues, such as polyps.
  • Sigmoidoscopy: A test similar to colonoscopy, this procedure uses a shorter tube to examine only the rectum and lower colon for cancerous changes.
  • Stool DNA Testing: A newly-approved procedure that tests stool samples for abnormal DNA associated with colorectal cancer.
  • Barium Enema: Also called a lower GI series, a silver-white metallic compound in inserted through the rectum. This compound coats the interior of the colon and rectum, allowing for better visualization of abnormalities when X-rays are taken.
  • Virtual Colonoscopy: Also called colonography, this procedure using a series of X-rays (computed tomography) to create a detailed image of the colon and rectum.
  • Biopsy: Abnormal-looking cells are extracted and checked by a pathologist for cancerous signs.
  • Genetic Testing: A genetic test of the cells extracted during biopsy can show whether the cancer is sensitive or resistant to specific treatments, so your care team can plan the most effective regimen against the disease.
Other tests that may be used for diagnosis or further evaluation include magnetic resonance imaging (MRI), positron emission tomography (PET) and ultrasound scans.
For early detection of colorectal cancer, the American Cancer Society currently recommends, beginning at age 50, either:
  1. colonoscopy every 10 years
  2. sigmoidoscopy, virtual colonoscopy or barium enema every 5 years
  3. stool DNA test every 3 years
These guidelines are for people with average colorectal cancer risk. Those with elevated risk should consider starting screening at a younger age and be screened more frequently.
Staging Colorectal Cancer
To properly plan for treatment, colorectal cancer patients are staged in accordance to how advanced the disease is. This is primarily done by taking a number of factors into consideration, including:
  • Size of the tumor
  • If the tumor has grown into a blood vessel or adjacent organs, such as the stomach or small intestine
  • Whether the cancer has spread to nearby lymph nodes and how many lymph nodes are affected
  • Whether the cancer has metastasized to distant organs
  • If the cancer can be completely removed by surgery
  • The cancer cells’ appearance (how abnormal they look) when examined under a microscope
Based on these factors, patients are staged according to their risk level, with higher risk patients typically requiring more intensive treatments.
More information on colorectal cancer staging criteria is available on the National Cancer Institute’s website.
If you have been diagnosed with colorectal cancer or are looking for a second opinion consultation about your treatment, find out more about becoming a patient by calling 800-826-HOPE or filling out the Request a New Patient Appointment Online form.