Lab Tests for Cancer

How is cancer diagnosed?

When cancer is suspected, your healthcare provider will do a complete evaluation. This includes a complete health history, a physical exam, and diagnostic testing. Many tests may be needed to figure out if you have cancer, or if another condition (like infection or inflammation) is causing cancer-like symptoms.

Diagnostic testing is used to confirm or rule out the presence of disease, watch the disease process, plan for treatment, and see how well treatment is working. In some cases, repeat testing is needed when a person’s condition has changed. Repeat testing may also be needed if a sample collected was not of good quality, or to confirm an abnormal test result. Diagnostic procedures for cancer may include imaging scans, lab tests, tumor biopsy, endoscopic exam, surgery, or genetic testing. The most common test used to diagnose cancer is a tissue or needle biopsy.

What are the different types of lab tests?

Clinical lab testing uses chemical processes to measure levels of certain components in body fluids and tissues. The most common samples used in clinical lab tests are blood and urine samples. Many different tests can be done to find and measure many different chemicals in blood or urine. Some of the things that can be measured include blood glucose (sugar), electrolytes (like calcium and potassium), enzymes, hormones, fats (lipids), other metabolic substances, and proteins.

Here are descriptions of some common lab tests used when diagnosing cancer:

Blood tests

Different blood tests are used to check the levels of substances in the blood that show how healthy the body is and if infection is present. For instance, blood tests can show things like:

• High (elevated) levels of waste products, like creatinine or blood urea nitrogen. This is a sign that the kidneys are not working well enough to filter those substances out.

• Electrolyte levels. These are chemical compounds, like sodium and potassium, that the body needs to work well.

• How quickly the blood clots. These tests are called coagulation studies.

• The complete blood count (CBC). This test measures the size, number, and maturity of the different blood cells in a specific volume of blood. This is one of the most common tests used. A CBC may be done to help diagnose certain blood cancers, such as leukemia and lymphoma. It can also be used to get an idea of your overall health and find other problems that are not cancer, like anemia or infection.

  • Red blood cells are important for carrying oxygen and fighting anemia and fatigue. The hemoglobin part of the CBC measures the oxygen-carrying capacity of the red blood cells. The hematocrit part measures the percentage of red blood cells in the blood.

  • White blood cells fight infection. Increased numbers of white blood cells may mean there is an infection.

  • Platelets keep the body from bleeding and bruising easily.

Urinalysis

Urinalysis (UA) breaks down the components of urine to check for drugs, blood, protein, and other substances.

Blood in the urine (hematuria) may be caused by a benign (not cancer) condition, like an infection or prostate swelling. But it could also be a sign of cancer in the prostate, bladder, or kidneys.

High levels of protein in the urine (proteinuria) may be a sign of a kidney or heart (cardiovascular) problem. But depending on other symptoms, proteinuria could be a sign of a blood cancer called multiple myeloma, and more urine tests may be needed.

Tumor markers

Tumor markers are substances either made by cancer cells and released into the blood or urine. Or they are substances created by the body in response to cancer cells. Tumor markers are used to see how well cancer is responding to treatment and to check for cancer recurrence (when it comes back after treatment). Tumor marker levels change over time. The trend in the levels is important. For instance, if levels are high at diagnosis, but steadily go down as treatment goes on, it's a good sign that treatment is working. On the other hand, if levels went down for a while, but then start to go up, the cancer may not be responding to treatment anymore. A new treatment plan may be needed.

Research is currently being done on how tumor markers might be used to find (detect), diagnose, and treat cancers.

Tumor markers can help find possible problems. They're often used to monitor cancer after treatment. But in most cases they must be used along with other tests because:

• Cells other than cancer cells also produce tumor markers. So people with diseases or conditions that are not cancer may also have high levels of these substances in their blood.

• Not every person with cancer has tumor markers.

• Some tumor markers are not specific to any one type of cancer.

• Tumor marker levels might not go up until cancer gets worse.

Here are brief descriptions of some of the tumor markers used for cancer:

• Prostate-specific antigen (PSA). A little bit of PSA is always present in the blood of adult males. An elevated blood PSA level may be a sign of prostate cancer. But other conditions, such as benign prostatic hyperplasia (BPH) and prostatitis (inflammation of the prostate), can also raise PSA levels. It's most useful to see if and how fast the PSA level goes up over time. PSA levels are used to see how a person has responded to treatment and to watch for cancer recurrence.

• CA 125. Ovarian cancer is the most common cause of elevated CA 125. But cancers of the endometrium, fallopian tubes, cervix, pancreas, liver, breast, lung, and digestive tract can also raise CA 125 levels. Several non-cancer conditions can also elevate CA 125, like uterine fibroids and pregnancy. CA 125 is used mainly to monitor treatment and recurrence of ovarian cancer.

• Carcinoembryonic antigen (CEA). CEA is normally found in small amounts in the blood. Colorectal cancer is the most common cancer that makes this tumor marker go up. Other cancers that can also raise CEA levels include pancreas, lung, breast, ovary, and thyroid cancers. Noncancer conditions that can raise blood CEA include arthritis, hepatitis, and cigarette smoking.

• Alpha-fetoprotein (AFP). AFP is normally elevated in pregnant women because it's made by the fetus. But only low levels of AFP are found in the blood of adults. In men, and in women who are not pregnant, a high level of AFP may be a sign of liver cancer or cancer of the ovary or testicle. Noncancer conditions, like liver disease and inflammatory bowel disease may also cause somewhat elevated AFP levels.

• Human chorionic gonadotropin (HCG). HCG is another substance that appears normally in pregnancy and is produced by the placenta. If pregnancy is ruled out, HCG may indicate cancer in the testis, ovary, liver, stomach, pancreas, and lung. Marijuana use can also raise HCG levels.

• CA 19-9. This marker is linked to cancers in the colon, stomach, and bile duct. High levels of CA 19-9 may indicate advanced cancer in the pancreas. But it is also linked to noncancer conditions, including gallstones, pancreatitis, cirrhosis of the liver, and cholecystitis.

• CA 15-3. This marker is most useful in evaluating the effect of treatment for women with advanced breast cancer. Elevated levels of CA 15-3 are also linked to cancers of the ovary, lung, and prostate. They are also linked to noncancer conditions such as benign breast or ovarian disease, endometriosis, pelvic inflammatory disease, and hepatitis. Pregnancy and lactation also can raise CA 15-3 levels.

• CA 27-29. This marker, like CA 15-3, is used to follow the course of treatment in women with advanced breast cancer. Cancers of the colon, stomach, kidney, lung, ovary, pancreas, uterus, and liver may also raise CA 27-29 levels. Noncancerous conditions linked with this substance are first trimester pregnancy, endometriosis, ovarian cysts, benign breast disease, kidney disease, and liver disease.

• Lactate dehydrogenase (LDH). LDH is a protein that normally appears all over the body in small amounts. Many cancers can raise LDH levels. So it is not useful in identifying a specific kind of cancer. But measuring LDH levels can be helpful in monitoring treatment for cancer. Noncancer conditions that can raise LDH levels include heart failure, hypothyroidism, anemia, and lung or liver disease.

• Neuron-specific enolase (NSE). NSE is linked to several cancers. But it is used most often to monitor treatment in people with neuroblastoma or small cell lung cancer.