From the moment that doctors begin to suspect that you have cancer until the time of your last cancer treatment, it feels like you are undergoing an endless series of tests. Some of them are simple blood tests that can take place at your doctor’s office during checkup visits or at outpatient laboratories like LabCorp and Quest diagnostics. Others are medical imaging tests that some doctor’s offices have the capability to perform but in other cases require you to visit an outpatient radiology center. Still, other types of tests, such as the tissue biopsies required to confirm a diagnosis of mesothelioma, require surgery and anesthesia; for these procedures, you must go to an outpatient surgery center or even be admitted to the hospital. It takes a lot of tests to make a diagnosis and even more to arrive at a treatment plan, which usually involves chemotherapy. During the course of your treatment, the blood tests become even more frequent. Based on the results of these tests, your doctors gain valuable information about how to proceed with your treatment.
The Three Types of Blood Cells
A complete blood count (CBC) is a blood test with many applications in medicine, from routine health screenings to the diagnosis of a wide variety of diseases to measuring a patient’s response to chemotherapy. An abnormal result on a CBC is usually just an indication for your doctor to do more tests; it is not enough on its own to confirm a diagnosis of a minor illness. The CBC measures the concentration of the three main types of cells in the body. These are the three categories of blood cells in the human body:
- White blood cells (WBCs) – Also known as leukocytes (from Greek words meaning “white cells”), these are the largest type of blood cell. Unlike other blood cells, white blood cells have a nucleus, so they look a lot like the diagrams of cells in your middle school science textbook. Hematopoietic stem cells in the bone marrow produce WBCs, and then the cells circulate through the body in the bloodstream and the lymphatic system. Types of WBCs include T cells, B cells, and natural killer cells, among others. WBCs play an important role in the body’s immune response; the various types of WBCs produce antibodies and destroy infectious bacteria, viruses, and fungi. Having a higher-than-normal WBC count can be a sign of infection, but it is not a problem by itself; it could just mean that your body is successfully fighting the infection. A high WBC count can also be a sign of an autoimmune response. A low WBC count is more of a cause for concern because it means that the body has less ability to fight infections.
- Red blood cells (RBC) – also called erythrocytes (from Greek words meaning “red” and “cell”), haematodes, and corpuscles, the main function of these cells is to carry oxygen to all the organs and tissues of the body and then transport carbon dioxide to the lungs to be exhaled. These disc-shaped cells are very tiny so that they can pass through the capillaries to transport oxygen to the body’s various tissues. They also play a role in immune response, using a compound called hemoglobin to destroy bacteria and other pathogens. One of the reasons that RBCs are so small is that they do not have a nucleus or mitochondria; therefore, they have no DNA. This means that they do not use any of the oxygen that they carry. It also means that they cannot reproduce. RBCs are produced in the bone marrow and have a lifespan of about 120 days, after which they are dissolved in the spleen. A low RBC count is called anemia, and its main symptom is fatigue. Common causes of anemia include insufficient iron in the diet and various genetic and autoimmune diseases. Some causes of high RBC count include dehydration and kidney disease.
- Platelets – Also known as thrombocytes (from Greek words meaning “clot” and “cell”), platelets are also tiny cells that lack a cell nucleus. They are about one-fifth the size of red blood cells. The cells that produce platelets are called megakaryocytes, which are found in the lungs and the bone marrow. The main function of platelets is to form blood clots. When a blood vessel gets injured, the blood clots stick together at the site of the injury, so that they can stop the bleeding quickly. If your platelet count is too low, you run the risk of excessive bleeding, and you may bruise easily. You might have nosebleeds or find that your gums bleed spontaneously; there might also be blood in your bowel movements.
Kidney Function Tests
The main function of the kidneys is to filter substances out of the body that will be harmful if they build up in the bloodstream and then to send them to the bladder where they will be excreted in the urine. One of the products that the kidneys must filter out of the body on a regular basis is creatinine, a protein produced by the muscles as part of their normal function. If your kidneys are healthy, they eliminate creatinine from the bloodstream at about the same rate as the muscles produce it; therefore, your blood creatinine levels remain stable over time. If your kidneys are not functioning as they should, blood creatinine levels increase over time, as the kidneys cannot eliminate creatinine as fast the muscles produce it. Urine tests are another way to measure the function of the kidneys.
The Role of Blood Testing in Chemotherapy Treatment
You will need a lot of blood tests and imaging tests before you start chemotherapy. Your medical team will test the function of your heart, lungs, liver, and kidneys. The liver and kidney tests are especially important because these organs are responsible for removing the chemotherapy drugs from your body after they have done their job. Some research indicates that glomerular filtration rate (GFR), which is the speed that fluid flows through the kidneys, is a more relevant measure for chemotherapy decisions that blood creatinine levels; GFR can be measured through a blood test or urine test. You will also need to have the levels of each kind of blood cell tested. This is because chemotherapy causes stress to many organs of the body, and doctors need to know what your baseline levels of function for these organs are, and therefore what doses of chemotherapy drugs you can expect to tolerate.
What Decisions Will Your Doctors Make Based on the Results of Your Bloodwork?
Chemotherapy treatment plans are modifiable by nature. Depending on the timing of your chemotherapy sessions, you will have blood tests after every session or after every few sessions. The results of the blood tests help your medical team decide whether to adjust the doses of your chemotherapy drugs, change the timetable for chemotherapy sessions, or even switch you to different drugs. For example, if your chemotherapy regimen is putting too much stress on your kidneys, then you will have to switch to lower doses of the drugs and prolong the timetable of treatment.
Low white blood cell count as a side effect of chemotherapy is a potentially serious complication since it is dangerous to get an infection when you already have cancer. With a suppressed immune system, you are vulnerable to all kinds of infections, but the most common types of infections seen as a complication of chemotherapy-related immune suppression are infections of the respiratory tract, urinary tract, mouth, genital area, and anus. If your white blood cell count is low, your doctors might give you antibiotics to stop infections before they start. If you only have one lung, you do not want to risk it getting infected. There are also medications that can increase your white blood cell count.
Anemia, which is a low red blood cell count, is also a common side effect of chemotherapy drugs. Symptoms of anemia include tiredness, dizziness, shortness of breath, and feeling cold. If your red blood cell count becomes low during chemotherapy, your doctors may prescribe medication to stimulate red blood cell production. They might also give you a blood transfusion.
Another type of blood test administered during chemotherapy treatment is the blood metabolic panel. Chemotherapy drugs can make you deficient in minerals such as potassium, magnesium, phosphate, and sodium. Based on the results of these tests, your doctors might decide to supplement these missing minerals through oral or intravenous administration or they might decide to change your chemotherapy medication doses and timing.
If there is a silver lining to all of this, it is that, through all this monitoring of the various organs and tissues of your body, you get to see the chemotherapy drugs working and see your body fighting back against cancer. Likewise, even though chemotherapy might make you feel worse before you feel better, all these tests let the doctors know how much is too much and when to give your body a break before chemotherapy can cause permanent damage.