The Oncoscint scan is a nuclear imaging test that is used to detect recurrences of ovarian or colorectal cancer. For the oncoscint scan, you receive an intravenous injection of a radioactive tracer bound to a specific protein (monoclonal antibody) that is attracted to the cell surface of colorectal and ovarian cancer cells. A special scanning camera records the movement and distribution of this radioactive material throughout your body; areas of increased uptake may represent ovarian or colorectal cancer cells. The camera data are then translated by computer into two-dimensional images that are recorded on film.
Purpose of the Oncoscint Scan
To identify and locate recurrent ovarian or colorectal cancer in people with elevated blood levels of certain tumor markers
Who Performs It
A physician or a technician who specializes in nuclear medicine performs this test.
- This test should not be performed in pregnant or breastfeeding women because of possible risks to the fetus or infant.
- Because the radiotracer may concentrate in areas of degenerative joint disease, abdominal aortic aneurysms, abdominal inflammatory processes, or inflammatory bowel disease, false-positive results may occur if these disorders are not identified before the test.
- This scan may also give false-negative results up to 30 percent of the time.
- Because the monoclonal antibody used for this test is derived from a mouse, up to 40 percent of people who undergo this scan develop human antimurine antibodies (HAMA). These antibodies may cause falsely elevated levels of certain tumor markers (CEA and CA 125) on later blood tests.
Before the Oncoscint Scan
- An abdominal CT scan is usually performed before the test to identify other conditions that could produce increased uptake of the radioactive material and distort the test results.
- Do not eat or drink after midnight, unless approved by your doctor.
- Do not expose yourself to barium 3 to 4 days prior.
What You Experience
- A physician injects the radiotracer-antibody combination into a vein in your hand or arm.
- You may go home after the injection. You will be asked to return 48 to 72 hours later for the scanning procedure.
- You will lie on a padded table. A large scanning camera, which records the gamma rays being emitted by the radioactive material, is passed over the front and back sides of your chest, abdomen, and pelvis.
- Additional scans may be performed 24 and 48 hours later.
- If a significant amount of radioactive material is observed in your bowel on the scans, you may be given a laxative or enema to provide a better view of the rest of the abdomen and aid in the interpretation of the images.
- The scanning procedure is done in two parts, on two separate days. Each one takes about 1 hour.
Risks and Complications
- The trace amount of radioactive material used in this test is not associated with significant risks or complications.
- Fewer than 4 percent of patients react to the monoclonal antibody used in this test by developing a slight fever, a rash, low blood pressure, or a headache. Rarely, chest or joint pain may occur.
After the Oncoscint Scan
- You may leave the testing facility and resume your normal activities.
- Drink extra fluids to help your body eliminate the radioactive material.
- Blood may collect and clot under the skin (hematoma) at the injection site; this is harmless and will resolve on its own. For a large hematoma that causes swelling and discomfort, apply ice initially; after 24 hours, use warm, moist compresses to help dissolve the clotted blood.
- A physician analyzes the recorded images for evidence of recurrent colorectal or ovarian cancer.
- If no abnormality is found, your doctor will recommend careful monitoring of your condition.
- If cancer recurrence is detected, appropriate therapy will be started.
The Johns Hopkins Consumer Guide to Medical Tests
Simeon Margolis, M.D., Ph.D., Medical Editor
Updated by Remedy Health Media