Doctors use many different types of tests to diagnose cancer and to determine if the disease has spread, and if so how far it has spread. Some tests help determine which treatments will work best for a particular person. Diagnostic tests can involve simple the use of x-ray, MRI, blood or urine tests, or biopsy. The tests a doctor selects depends on the type of cancer suspected, symptoms, age, and medical condition, and the results of other tests.
Laboratory tests involve testing a sample of blood, urine, and sometimes other body fluids. A common test is a href=”/content/view/297/41/”>complete blood count (CBC). A CBC measures the components of the blood, including white blood cells, red blood cells, and platelets. Leukemia, for example can be suspected based on the results of the CBC. Blood tests are also used to monitor side effects of cancer treatment, such as anemia or infection. There are tests which measure specific proteins in the blood which correlate with (but do not defintely diagnose) cancer. An example is the CA-125.
Specific laboratory tests help doctors make treatment decisions. For example, the breast cells of women with breast cancer may be tested to determine whether the cells have the estrogen receptor, which lets doctors know whether these women will respond to hormone-based treatment. Also, the breast cancer drug trastuzumab (Herceptin) is only effective in people whose breast cells have HER2/neu (a protein). Some tests can be used to determine if cancer has returned, although this use differs for each cancer.
X-ray is not as sophisticated as newer procedures, but they are still useful for finding and monitoring some types of tumors. Imaging tests help determine whether cancer has spread to other areas in the body, and to evaluate the size and location of the tumor. Magnetic resonance imaging (MRI) uses electromagnetic waves to create computer-generated pictures of the inside of the body. Ultrasound creates pictures of the inside of body using high-frequency sound waves. Computed tomography (CT or CAT) scan creates a three-dimensional picture of the inside of the body using a series of x-ray pictures that are taken from many different angles. A computer compiles these images into a detailed, cross-sectional view. Positron emission tomography (PET) scan is a procedure in which radioactive sugar molecules, called tracers, are injected into the body in a low dose, radioactive form. During the scan, the cancer cells “light up,” because the cancer cells absorb sugar faster than normal cells. Bone scan is used to determine if bone is damaged, either from cancer or from some other cause. A radioactive tracer is injected into a person’s body. If the bone is damaged, the tracer will concentrate in the bone. Also Integrated PET-CT Scans are sometimes used. Imaging tests alone can only identify the presence, size, and location of a mass, but are not specific enough to diagnose cancer.
Any medical procedure performed with an endoscope is called an endoscopy. An endoscope is a thin, flexible, lighted tube that is used to look at the inside of the body. The exact type of endoscope varies depending on what part of the body needs to be viewed. The following are some common examples of endoscopic tests.
- laparoscopy uses a laparoscope to examine the abdominal area.
- bronchoscopy uses a bronchoscope to examine the lungs.
- colonoscopy uses a colonoscope to examine the colon and rectum.
In many cases, a diagnosis of cancer is made with biopsy. This test involves removing all or part of the tumor and examining the sample under the microscope to determine if cancer cells are present. There are different types of biopsies:
- Fine needle aspiration biopsy: a fine needle biopsy may be the first type of biopsy done on tumors that can be felt by the doctor. The doctor uses a very thin, hollow needle in a syringe to gather a small amount of fluid and cells from the suspicious area.
- Vacuum-assisted biopsy: vacuum pressure (suction) is used to pull the sample tissue through a specially designed hollow needle in this biopsy method. This gives the doctor the ability to collect multiple or larger samples from the same biopsy site without having to insert the needle more than once.
- Incisional biopsy: removes a piece of the suspicious area for examination. An incisional biopsy may be used for soft tissue tumors, such as those arising from muscle or fat, to distinguish between benign lumps and cancerous tumors called sarcomas.
- Image-guided biopsy: an image-guided biopsy is a procedure in which the doctor uses imaging technology, such as ultrasound, fluoroscopy, CT scan, x-ray, or MRI scan, to determine the exact location from which the tissue sample will be removed for analysis. A needle is used to obtain a sample of the tissue from the site; the needle type used may be a fine needle, core needle, or vacuum-assisted needle. An image-guided biopsy may be used when a tumor appears on an imaging scan, such as an x-ray, but cannot be felt by the doctor, or when the area is located deeper inside the body. The type of imaging technology used depends on the location of the biopsy site and other factors.
- Core needle biopsy: the size of the syringe needle used in a core needle biopsy is larger than the one in a fine needle biopsy, so that a cylinder of tissue can be obtained. If a fine needle biopsy cannot provide a definitive diagnosis, the doctor may want to do a core needle biopsy. Core biopsies are often performed instead of fine needle aspiration biopsies because they provide more tissue to review.
- Surgical biopsy: unlike the needle methods described above, in a surgical biopsy, a surgeon makes an incision in the skin and removes some or all of the suspicious tissue. It is often used after a needle biopsy shows cancer cells, or it can be used as the first method to obtain tissue for diagnosis. There are two main categories of surgical biopsies, excisional and endoscopic.
- Bone marrow biopsy. The doctor uses a large, rigid needle to go through a bone, often the back of the hip bone, and into the marrow in order to gather a sample. A core biopsy of the bone may also be performed at the same time. A bone marrow biopsy is used to determine if a person has a blood disorder or a blood cancer, including leukemia and multiple myeloma. It can also be used to find out if a cancer that originated in another part of the body has spread to the bone marrow.