Waiting for test results that could indicate a cancer diagnosis can be extraordinarily stressful. Even worse, most of the time, a test result does not simply lead to your doctor making a treatment plan; instead, the only answer you can get from most test results is that you need more tests. You have probably heard that blood tests alone are not enough to lead to a clear diagnosis of mesothelioma or another other kinds of cancer, and this is true, and yet, it seems like doctors order an endless series of blood tests for patients who have been diagnosed with mesothelioma or who are waiting for a diagnosis. Blood tests are an important part of assessing the progression of the disease, and they can also help doctors make informed decisions about how well the treatment plan is working and whether it needs adjustment. As of 2022, there is no blood test that, alone or in combination with other blood tests, can give a definitive diagnosis of mesothelioma. Meanwhile, researchers are constantly working to develop minimally invasive tests, such as blood tests, that can accurately diagnose mesothelioma and other cancers when they are in their early stages and easiest to treat, but so far, no such test has been developed for the point where it has proven itself suitable for clinical use.
Blood Tests Alone Cannot Diagnose Mesothelioma
Blood tests can tell you that something is not right with your health, but they cannot tell you for certain that the underlying cause of your symptoms is mesothelioma. To make that diagnosis, doctors first do imaging tests, such as chest X-rays or CT scans of the abdomen, and if they see an abnormal mass, they will surgically remove cells from it and analyze those cells to see if they are cancerous; this procedure is called a biopsy. After cells are removed for a biopsy (the cell removal part of the procedure requires one of several types of surgeries, depending on the location of the tumor), a pathologist examines them under a microscope. The biopsy will determine whether the cells are benign (not cancerous) or malignant (cancerous). The pathologist will also be able to tell by looking at the cells whether they indicate mesothelioma or another type of cancer. Most mesothelioma tumors are made of epithelioid, sarcomatoid, or biphasic cancer cells, and based on the biopsy, your doctor will know which type you have. (Most cases of mesothelioma involve one of these three types of cells; many other types of mesothelioma cancer cells have been found in the biopsies of mesothelioma patients, but these other types are rare.)
A buildup of fluid in the chest cavity or abdomen is a symptom in many cases of mesothelioma; if the fluid buildup is in the chest, it is called pleural effusion, and if it is in the abdomen, it is called ascites. Doctors sometimes remove this fluid. Removing it serves two purposes, first, to relieve discomfort, and second, to test the fluid for the presence of cancerous cells. If there are cancer cells in the fluid, it means that cancer has spread.
The Complete Blood Count and Its Role in Mesothelioma Testing and Treatment
The complete blood count (CBC) is a very common blood test; chances are, you have had this test performed even if you have never had a health problem serious enough to require hospitalization. It is usually one of the first things nurses do when patients visit the emergency room, and some doctors order a CBC as part of a routine physical. The CBC can be very useful in diagnosing diseases and monitoring a patient’s overall health, but it is only useful for diagnostic purposes when done in combination with other tests. Any abnormal result on a CBC could indicate dozens of different problems.
Humans have three different types of blood cells. Red blood cells, also known as erythrocytes, carry oxygen from the lungs to all the other cells of the body and then carry carbon dioxide back to the lungs. If the red blood cell count is too low, it could indicate a deficiency of iron, vitamin B12, or folate; it could also be due to blood loss from an injury. If it is too high, it could indicate a heart or lung disease, because the cells of the body need more oxygen, so the body produces more red blood cells to transport the oxygen. White blood cells, also known as leukocytes, are responsible for the body’s immune response; eosinophils, macrophages, mast cells, lymphocytes, and neutrophils are different types of white blood cells. If the white blood cell count is high, it indicates that there is an infection that your immune system is trying to fight, and if it is low, it indicates a poor immune response; it does not tell you what kind of infection or anything about the cause of the immune suppression. Platelets are the cells that form clots to stop bleeding. A high platelet count can be due to inflammation, a recent traumatic injury, or iron deficiency, and a low platelet count is usually due to autoimmune disease or the side effects of anticoagulants (blood thinners) or chemotherapy drugs.
The CBC tests can be very useful when doctors are trying to decide whether to adjust a medication dose. For example, if they have given you immune-suppressing drugs to manage an autoimmune disease, they want to make sure that your white blood cells are low enough to suppress the autoimmune response but that they are not so low that you are in immediate danger of getting seriously ill from infections that only cause mild illness in people with healthy immune systems. If your mesothelioma treatment plan includes chemotherapy, your doctor will probably perform CBC tests frequently, since chemotherapy drugs have an effect on the various types of blood cells.
What Is a Biomarker?
“Biomarker” is a general term for anything that doctors are looking for when they do a blood test or almost any other kind of diagnostic test. For example, some pregnancy tests are performed on blood and others on urine, but in either case, they are looking for the same biomarker, namely human chorionic gonadotropin, a hormone that increases rapidly during early pregnancy, but which is present in men and nonpregnant women only at levels too low to be detected by the tests. Many different compounds are higher in the blood of cancer patients than of cancer-free people; these compounds are called tumor markers, and they include a wide variety of carbohydrates, proteins, conjugated proteins, and peptides. Different tumor markers are associated with different cancers.
Biomarker blood tests are also not sufficient to make a cancer diagnosis, although they can give information about whether the cancer is growing or shrinking. For example, many men receive blood tests for a biomarker called prostate-specific antigen (PSA). If it is elevated, it shows that there is something unusual going on with the prostate, but it cannot tell you whether that something is prostate cancer, an infection, or simply benign, age-related prostate enlargement. You may have had the experience of your doctor telling you that your PSA was elevated, and then losing sleep until your doctor did more tests and reached the conclusion that, while you do not have prostate cancer, you are no spring chicken.
Why Do Doctors Order the Mesomark Test for Mesothelioma Patients?
Mesothelin is a protein that is present in the mesothelial cells of the pleurae (the linings of the chest cavity), even in healthy people. This protein can be used as a tumor marker because, while people who do not have cancer tend to have about 80 ng/mL of mesothelin in their bloodstream, as detectable by blood tests, the levels tend to be much higher for people who have been diagnosed with certain kinds of cancers. Approximately two-thirds of people with mesothelioma, ovarian cancer, and lung cancer have elevated levels of mesothelin. As with any biomarker, the mere presence of mesothelin on a blood test is not enough to enable a doctor to make a diagnosis of mesothelioma or any other kind of cancer.
As with other biomarkers, your levels of mesothelin can be a useful indicator of your response to treatment. If your mesothelin levels are consistently decreasing, it means that the treatment is working. Mesomark is a blood test that measures mesothelin levels to help assess mesothelioma patients’ response to treatment.
Mesothelioma Research Is Constantly Evolving
Developing accurate, minimally invasive tests to detect cancer at the earliest possible stage is a priority for medical research. Many new articles are published each year on studies assessing the reliability of new tests and treatments. The Mesothelioma Applied Research Foundation (Meso Foundation) is dedicated to informing patients and their families about the latest research on tests and treatments for mesothelioma. If you ask your doctor, they will be able to tell you about how much cancer treatment has evolved since they started practicing medicine. Researchers are constantly looking for new applications for existing tests, ways to improve on current testing and treatment protocols, and even entirely new therapies.