There are many standard laboratory tests that involve an analysis of blood, urine, or stool to detect abnormalities that might indicate cancer. Some lab tests are precise, reliable indicators of specific health problems. Others provide more-general information that is helpful in ruling out conditions or providing baseline information.
Information obtained from lab tests may help your doctor decide whether other tests or procedures are needed to make a diagnosis. The information may also help the doctor develop or revise your treatment plan. Different tests can be used throughout the course of treatment to track the body’s response to therapy. The results of lab tests are unique to each person. Although they are compared with what is considered “normal” in the population as a whole, “normal” for you is not necessarily the same as for someone else. We encourage you to discuss the results of testing with your doctor and to ask questions if you don’t understand the results.
There are many sophisticated tools, such as X-rays, computerized axial tomography, magnetic resonance imaging, and ultrasound, that provide a relatively noninvasive way to take a look inside the body. Imaging plays an important role in initially screening for cancer, determining the best course of treatment by pinpointing the size and the location of cancer, tracking a cancer’s response to treatment, and monitoring for possible recurrence over the long term.
Most people are familiar with X-ray imaging. Images produced by X-rays are due to the different absorption rates of different tissues. For example, bones, soft tissues, and even air show up as different shades on an X-ray. The most familiar use of X-ray technology is checking for broken bones, but X-rays are also used in cancer diagnosis. Chest radiographs and mammograms are often used for early cancer detection or to see if cancer has spread to the lungs or other areas in the chest. Mammograms are used to look for tumors or suspicious areas in the breasts.
A mammogram is an X-ray image of the breast. Screening mammograms are used to check for breast cancer in women who have no signs or symptoms of disease. The X-ray images make it possible to detect tumors that cannot be felt. Diagnostic mammograms are used to check for breast cancer after a lump or other symptom has been detected.
Computerized Axial Tomography
Computerized axial tomography (CT) is a diagnostic procedure that uses X-ray equipment in conjunction with a computer to create cross-sectional images of the body. The CT equipment displays detailed images of organs, bones, and other tissues. CT scans are used to determine the presence of a tumor, provide information about its size and location, guide a biopsy procedure, help plan for surgery or radiation, and determine whether the cancer is responding to treatment.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) uses radio waves in the presence of a strong magnetic field to produce three-dimensional images of sections of the body. Different tissues (including tumors) emit a more- or less-intense radio signal based on their chemical makeup, creating a detailed picture of organs and tissues.
Positron Emission Tomography
Positron emission tomography (PET) is used to generate computerized images of chemical changes in the body. Because cancerous tumors are usually more active than normal tissue, they look different on a PET scan. During a PET scan, a patient is given an injection of a substance that consists of a combination of a sugar and a small amount of radioactively labeled sugar. The radioactive sugar can help locate a tumor because cancer cells take up or absorb sugar more quickly than other tissues in the body. The PET scanner is used to detect the distribution of the sugar in the tumor and in the body.
Combined CT/PET Scanning
Combined CT/PET scanning joins two imaging tests—computerized axial tomography and positron emission tomography—into one procedure. Combining CT with PET scanning may provide a more complete picture of a tumor location, growth, or spread than either test alone. The combined CT/PET scan may also reduce the number of additional imaging tests and other procedures a patient needs.
An ultrasound uses sound waves with frequencies above those that humans can hear. The ultrasound sends sound waves traveling into the body, which are then reflected back from organs and tissues, creating a picture of the internal organs. Ultrasound can show tumors and can also guide doctors doing biopsies or treating tumors.
Endoscopy is a way of looking inside the body using a flexible tube that has a small camera on the end. A colonoscopy is a common type of endoscopic procedure that is used to look for signs of colon cancer. Another common type of endoscopy is laparoscopy, which is used to look at the ovaries or other abdominal organs. Small instruments can be inserted through an endoscope and used to take samples of tissues that look abnormal during the procedure.