When we suspect cancer, the biggest question that comes to our mind is, 'Can this be detected in the blood?' In fact, doctors use various methods to diagnose cancer, see its stage, and plan treatment. Among these, blood tests are one important tool. However, it is important to remember that blood tests alone are often not enough to confirm cancer.
Can cancer be diagnosed with just a blood test?
Simply put, most cancers cannot be diagnosed with a blood test alone. However, some blood cancers can be detected this way. Here are a few examples:
- Hodgkin lymphoma
- Non-Hodgkin lymphoma
- Leukemia
- Multiple myeloma
These can be detected to some extent through blood tests, but other solid organ cancers, such as lung, breast, and colon, are difficult to detect through blood tests alone.
What types of blood tests are used to detect cancer?
Doctors divide blood tests for cancer into four main types. Let's take a look at what they are.
Complete Blood Count (CBC)
This is a common blood test that is often done. Some blood cancers, such as leukemia and lymphoma, can be identified with this (CBC) test. It also helps your doctor get an idea of how your body is responding to treatment and whether the cancer has spread to your bone marrow. However, it cannot detect cancers such as lung, breast, or colon cancer.
Tumor Marker Blood Tests
These tests look for certain chemicals that our bodies produce every day in our blood. If there are too many of these chemicals in the blood, it can be a sign of cancer. For example, the `CA-125` test is often used to plan treatment for ovarian and pancreatic cancers and to see if the cancer has come back. The other is the `PSA (prostate-specific antigen)` test. This `(PSA)` is a protein produced by the `(prostate)` gland in men. An increase in the `(PSA)` level in the blood can be a sign of prostate cancer.
Blood Protein Tests
These tests look for abnormal levels of proteins in your blood. Very high protein levels can be a sign of blood cancers, especially leukemia, lymphoma, and multiple myeloma. Some tests, such as the Comprehensive Metabolic Panel (CMP), simply include a total protein test. That can also provide this information.
Circulating Tumor Cell (CTC) Tests
This is actually a type of liquid biopsy. It looks for cancer cells in your blood. Sometimes small pieces of cancer cells can break off and get into your blood. Doctors use this test to predict the future outcome of people with metastatic breast, prostate, or colon cancer. If the level of CTCs in your blood is low, or even undetectable, that's a good sign. But if there are a lot of CTCs in your blood, that's not a good sign, and you may need additional treatment.
What other tests are needed to confirm cancer?
As I mentioned before, blood tests alone are usually not enough to confirm cancer. You will definitely need to have several other tests. Some of them are:
- ` Biopsy `: This involves taking a small tissue sample from a suspicious organ or bone marrow and sending it to a laboratory where it is analyzed.
- Imaging tests : These may include X-rays, CT (computed tomography) scans, MRI (magnetic resonance imaging) scans, or PET (positron emission tomography) scans. These can help the doctor find the location of cancerous tumors and determine their stage.
- Specialized tests : Sometimes other specialized tests may be needed. For example, a mammogram may be done to help detect breast cancer, or a Pap smear may be done to detect cervical cancer.
Can the early stages of cancer be detected through blood?
Many cancers do not show up on routine blood tests in their early stages. However, there are now specialized blood tests that can detect some cancers in their early stages.
- ` Galleri test` : This is a special blood test. It can detect more than 50 types of cancer! It uses a technology called `DNA sequencing` to find patterns that are unique to cancer. It can tell the doctor whether you have cancer and where it started.
- Proteomics-based plasma test : A 2024 study found that a new blood test could detect 18 types of cancer at an early stage. (Proteomics is the study of cellular proteins and how they work.) The study, which included 440 people, identified 93% of Stage I cancers in men and 84% of Stage I cancers in women. Although more research is needed, this blood test could become a standard way to detect cancer in the future.
The results of such tests should be interpreted with great care. Also, it is important to discuss further testing and treatment with a qualified doctor.
We know that it is very difficult to detect cancer in its early stages. However, routine cancer screenings can help detect some types of cancer before symptoms appear. Ask your doctor about screenings that are appropriate for your age. This will help you stay healthy.
How do blood tests for cancer work?
When combined with other tests, blood tests can provide your doctor with some important information. Think about it this way...
- Are there chemicals and proteins in your blood that indicate cancer?
- It could be due to cancer, whether the blood cell levels are too high or too low.
- What is the stage of the cancer ?
- How successful is the treatment ?
- Has the cancer come back (recurrence)?
How to prepare for a cancer blood test?
Your doctor will give you some specific instructions on how to prepare for your blood test. These instructions may vary depending on the type of test you are having.
Sometimes, you may be asked to ``fast'' for 8 to 12 hours before the test. This means you should not eat or drink anything except water. You may also be asked to stop taking certain medications before the test.
What to expect when taking a blood test?
It only takes a few minutes to take a blood sample from you. This is how the doctor or nurse does it:
- First, a tourniquet is tied around your upper arm.
- Then, a spot on your skin is cleaned, often on the inside of your elbow or on your hand.
- A needle is inserted into that area. At that time, you may feel a slight tingling sensation, like being bitten by an ant.
- Loosen the tight band a little.
- A tube is connected to the needle and blood is filled into it.
- Then both the band and the pin are removed.
- A little pressure is applied (pressed) to stop the bleeding from the puncture site.
- Finally, a bandage is applied to the area.
Very simple, right?
What to expect after the blood test?
After a cancer blood test, you will need to keep the plaster on for a few hours. Also, if your doctor advises you, you may need to avoid exercise for a few hours after the test. (If your heart rate increases, bleeding may increase.)
What are the risks or side effects of a blood test?
Blood tests are very safe, and the risks are very low. You may experience some bruising or swelling at the site of the needle. Very rarely, the vein may swell. If this happens, applying something warm (such as a warm cloth or a heating pad) may help.
When will I know my test results?
You will most likely get your results within a day or two. However, depending on the type of test being done, it may take several days.
Your doctor will tell you when to expect the results and how to discuss them with you at your appointment.
If my results are abnormal, what happens next?
If your blood test suggests that you may have cancer, your doctor will refer you to an oncologist. That specialist can do more tests to confirm the diagnosis and recommend an appropriate treatment plan.
Cancer treatment always requires a multidisciplinary team. Your oncologist will work with a variety of specialists to provide you with the treatment you need.
Can a lipid panel detect cancer?
No, doctors do not use lipid panels to detect cancer. A lipid panel is a test that measures the levels of cholesterol and triglycerides in your blood. It helps doctors see your risk of developing cardiovascular diseases, such as stroke and heart attack.
Even though my blood tests are normal, could I have cancer?
Yes, even if your blood test results are normal, you could still have cancer. The reason for this is that blood tests alone cannot detect most types of cancer. Some blood cancers, such as leukemia, lymphoma, and multiple myeloma, are exceptions to this rule.
Waiting to find out if you have cancer can feel like time has stopped. It can be hard to go about your daily life without knowing what tomorrow will bring. Your doctor will run a number of tests to confirm a diagnosis - and checking your blood for cancer is just one of them. They will explain to you what each test will do and what your results will mean.
Here are some of the most important things we need to remember in this article:
Okay, so we've talked a lot about cancer and blood tests today. In summary, here are a few things to remember:
- Blood tests are only one part of the cancer detection process. In many cases, blood tests alone cannot confirm cancer.
- Blood tests can provide clues about some blood-related cancers (Leukemia, Lymphoma).
- There are different types of blood tests, such as `(CBC)`, `(Tumor markers)`, `(Blood protein tests)`, and `(CTC tests),` and each of them looks at different things.
- To confirm cancer , additional tests such as a biopsy and imaging tests are required.
- New blood tests (Galleri test, Proteomics-based test) that can detect cancer in its early stages are also being researched, but they are not yet in general use.
- If you suspect you have cancer, seek medical advice immediately. They will tell you exactly what tests you need.
- Even if your blood test results are normal, let your doctor know if you have other symptoms, as not all cancers show up in the blood.
So, I hope this information is helpful to you. If you have any further questions about anything, don't hesitate to ask your doctor. They are the ones who can give you the best advice.
` Cancer, blood tests, tumor markers, CBC, diagnosis, cancer treatment, leukemia
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