Colorectal Cancer

How do we diagnose Colorectal Cancer?

Since early diagnosis is key, we perform screening examination to find the polyps as early as possible.
CT colonography, sometimes called CT Colonoscopy (CTC) or Virtual Colonoscopy (VC). This can be done purely as a screening exam or on those who have failed an optical colonoscopy exam or are at increased risk for complications from optical colonoscopy. Low-radiation CT images of the abdomen and pelvis are obtained after the large bowel is gently inflated with carbon dioxide. Subsequently, special software is used to create a 3-D images of the bowel. Specialist radiologists then interpret these images and reconstructions to find polyps and other abnormalities. This information can be provided to your doctor for further evaluation if necessary.
If tumor is found then the following examinations can be performed to “stage” (determine the extent of) the disease.
PET-CT (Positron Emission Tomography and Computed Tomography): We can tag a special molecule with a small amount of radioactive material, inject it into the body and then scan the body to detect cancer. This gives us an idea of where and how extensive the cancer is, either at the time of diagnosis or to determine if a particular treatment is having an effect.
MRI: High-resolution images of the abdomen and/or pelvis are obtained without radiation, using a combination of magnetic field and radio-frequency pulses. This is very helpful for accurate detection of cancer (particularly of the rectum). At Mecklenburg Radiology, we prioritize patient comfort and use high strength magnets to obtain this study – a rectal coil is therefore not necessary. We also often use MRI of the liver to detect if disease has spread to that order with high accuracy.
Regular CT (or CAT scan): Can be used in combination with the above exams to scan the body and determine areas of abnormality. This is the workhorse study in the vast majority of cases, and offers a very good overview of the disease process.

What is the difference between Colonoscopy and CT Colonography?

Both Optical Colonoscopy and CT Colonography require the use of laxatives to clear the bowel of stool prior to the study. However, CT Colonography does not require sedation – this ensures that the patient is free to return to their regular schedule much sooner. While Optical Colonoscopy is a very safe procedure overall, CT Colonography eliminates any risks related to the sedation and bowel perforation (as the images are obtained from outside the body without the need to insert a camera physically within the bowel). The cost of a CT colonography is significantly less as well. In addition, because a CT Colonography involves imaging the entire abdomen and pelvis it gives the radiologist the ability to diagnose other potential disease that would not be seen with an Optical Colonoscopy.
Potential downsides of CT Colonography include some limited ability to diagnose polyps smaller than 1 cm. Also, finding a worrisome polyp or tumor necessitates further evaluation using an Optical Colonoscopy to biopsy or resect the lesion. However, since polyps less than 1 cm are usually not significant and most screening studies do not find worrisome polyps, the above issues are not as commonly relevant. The other downside is the use of radiation, although newer techniques have significantly reduced the dose to the point that a CT Colonography has the same overall radiation dose that a person would get from natural background sources during 2 years.

How do we treat Colorectal Cancer?

Depending on the extent of disease and patient factors, colorectal cancer can be treated with surgery, radiation therapy and chemotherapy. These three modalities are often used in combination, with chemotherapy used to decrease the overall tumor burden and to minimize the chance of recurrent disease. Radiologists are not typically involved in treatment of colon cancer unless disease has spread to the liver in which case specialized minimally invasive image guided therapies are possible.