You may be wondering, "Can't this blood test I'm doing tell me if I have cancer?" This is a reasonable question for many people. Some blood tests can actually give some clues about cancer. But the most important thing to remember is that many types of cancer cannot be detected by a blood test alone . However, these tests are very important in the process of diagnosing cancer, treating it, and monitoring the disease. Today, let's talk about what these blood tests can and cannot tell us about cancer.
Can cancer be diagnosed with just a blood test?
Simply put, usually not. A blood test is like one piece of a puzzle. You need the other pieces to see the whole picture. That means that if a doctor suspects cancer, they will do several other tests in addition to the blood test to confirm it.
However, there are some types of cancer, especially blood-related cancers, that can provide a big clue about through a blood test. For example:
- Leukemia
- Lymphoma (Hodgkin lymphoma and Non-Hodgkin lymphoma)
- Multiple Myeloma
Because these are directly related to the blood or the immune system, we can get an idea about them from the changes in the cells in the blood.
Types of blood tests used for cancer
Doctors use different types of blood tests to check for cancer and to see how the body is responding to treatment. Let's take a look at the main types.
| Test Name | Simply put, what happens with this? |
|---|---|
| Complete Blood Count (CBC) | This is a very common test. It measures the number of red blood cells, white blood cells, and platelets in your blood. If your white blood cell count is abnormally high or low, it could be a sign of a blood cancer, such as leukemia or lymphoma. However, it cannot detect cancers that develop in organs such as the lungs or breasts. |
| Tumor Marker Blood Tests | Tumor markers are certain chemicals produced by cancer cells or by the body in response to cancer. These tests check for excess levels of these in the blood. Examples: PSA test , which checks for prostate cancer in men, CA-125 test, which checks for ovarian cancer in women. However, not all increases in these markers indicate cancer, as they can also be due to other reasons. |
| Blood Protein Tests | Abnormally high levels of proteins in the blood can be a sign of blood cancers, especially multiple myeloma. Sometimes, these protein levels are included in a test you have, such as a Comprehensive Metabolic Panel (CMP) . |
| Circulating Tumor Cell (CTC) Tests | This is a slightly more complicated test. It looks for small pieces of cells that have broken off from a cancer tumor and are circulating in the blood. It is most often used to get an idea of the prognosis of someone with metastatic breast, prostate, or colon cancer. |
What other tests will be needed besides blood tests?
Imagine that you have an abnormality in your blood test. That alone does not mean that the doctor has cancer. He or she will need to do several more tests to confirm it.
- Biopsy: This is the most important test that can 100% confirm whether or not cancer is present. This involves taking a very small piece of the suspicious organ or tissue and examining it under a microscope.
- Imaging tests: These can help determine the location and size of a tumor. Examples include X-rays, CT scans, MRI scans, and PET scans.
- Specialized Tests: There are specialized tests for some types of cancer. For example, a mammogram is used for breast cancer and a Pap smear is used for cervical cancer.
Can cancer be detected in its early stages with a blood test?
It is usually difficult to detect cancer in its early stages with a routine blood test. However, with the advancement of medical science, new testing methods are emerging.
For example, a special blood test called the Galleri test has been found to be able to detect more than 50 types of cancer. Also, research is being done on tests that can detect cancer at an early stage by studying the protein patterns in the blood (Proteomics). Although these are not yet very common in our country, they have the potential to revolutionize cancer detection in the future.
But remember, if you receive a new test result like this, you should definitely talk to your doctor to understand it fully and decide what to do next.
How do you prepare for a blood test?
The doctor will give you some special instructions before a blood test.
- Some tests may require fasting for about 8-12 hours. This means you cannot eat or drink anything other than water.
- You may be asked to stop taking some medications for a while before the test.
- Therefore, always follow the doctor's instructions exactly .
The blood draw only takes a few minutes. There is a slight stinging sensation when the needle is inserted, but it is very minor.
What to do if the results of the report are abnormal?
It can take a day or two, or even longer, for the results of a blood test to come back. If your report contains anything that raises suspicion of cancer, your doctor will refer you to a cancer specialist, an oncologist .
Then, the specialist doctor will perform the necessary tests, confirm the disease, and develop the most suitable treatment plan for you.
The most important thing is, don't panic if you see something unusual in the report. Only your doctor knows exactly what it means. Talk to him and explain it.
If my blood test report is normal, can I not get cancer?
This is an important question that many people ask. The answer is, yes, it is possible.
Just because a routine blood test is normal doesn't mean you have cancer 100% of the time. Because as we discussed earlier, many types of cancer (especially cancers that don't involve the blood, such as those that develop in organs) don't show up on routine blood tests.
I understand how difficult it can be to wait for test results after suspecting cancer. However, doctors perform several tests to arrive at an accurate diagnosis. Blood tests are just one step in that journey. Therefore, it is important to trust the medical team and follow their advice.
Take-Home Message
- A blood test alone cannot usually confirm the presence of cancer, but it is a very important tool in the diagnostic process.
- Some blood cancers, such as leukemia and lymphoma, can be detected with a simple blood test like a CBC.
- Although tumor marker tests such as PSA and CA-125 are helpful, their elevated values alone do not indicate the presence of cancer. They can also be elevated for other reasons.
- Other tests, such as a biopsy, are often needed to definitively confirm cancer.
- No matter what is in your report, don't worry about it alone. Always talk to your doctor, explain it, and get the necessary advice.
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