Do Blood Tests Detect Cancer?

Blood tests are a commonly used diagnostic tool in medicine, and are an important tool in the diagnosis and management of cancer. They can provide valuable information about the state of a patient’s general health, potential disease, organ functioning, and more. Blood tests alone are not used to diagnose cancer, but they can provide helpful clues that may lead to further testing and a diagnosis. 

How And Why Are Blood Tests Done?

High or low levels of specific substances in the blood, urine, or other body fluids can be a sign of cancer. Blood tests can be useful for getting more information regarding many types of cancer, especially blood cancers like Hodgkin's lymphoma, leukaemia, non-Hodgkin's lymphoma, and multiple myeloma. 

If your doctor suspects cancer, blood tests may be a part of the testing process. While blood tests can be a useful tool in the process of diagnosing diseases, they are not reliable on their own and need to be used in conjunction with other measures, such as biopsies, imaging, physical exams, mammograms, pap smears or other specialised tests. 

Routine blood tests can be used to establish a baseline for each person, allowing doctors to monitor changes and identify any abnormalities. Blood tests are also used to monitor treatment response in patients with cancer. Changes in blood cell counts and tumour marker levels can indicate the effectiveness of treatment and help doctors adjust treatment plans accordingly. 

In addition, blood tests can be used to detect cancer recurrence after treatment and to monitor patients for the long-term effects of cancer treatment.

The tests can be performed in a doctor's office, clinic, lab, or hospital by healthcare providers such as lab techs or nurses, and involve blood extraction from a vein via a thin needle. 

The collection of the blood sample for testing takes a few minutes, and the sample is then tested in the lab for signs of cancer, which may include actual cancer cells, proteins, or other substances made or influenced by cancer. The results could be ready in a few days or weeks, and your doctor should help you to understand their meaning.

Different Types Of Blood Tests

There are several types of blood tests used in the diagnosis and management of cancer. The clues given by blood tests can tell your healthcare provider what other tests or information may be needed in order to make a diagnosis. 

Blood tests appear to be more accurate at detecting blood cancers than at picking up solid tumours, but can be useful in both cases. The type of blood test used depends on the type of cancer suspected, and your doctor will determine which tests are appropriate for you. Some of the blood tests used in cancer diagnosis and treatment include:

Liver And Kidney Function Tests

There are several different blood tests used to assess liver and kidney function, which can assist in cancer diagnosis and treatment by providing a baseline assessment of liver and kidney function before starting cancer treatment.

Liver function tests (LFTs) measure the levels of various enzymes and proteins in the blood, which can indicate liver damage or dysfunction. LFTs can help diagnose liver diseases such as hepatitis, cirrhosis, and liver cancer, and monitor the liver's response to cancer treatment.

Kidney function tests measure the levels of various substances in the blood, such as the waste products which our kidneys are meant to remove from the blood. Unusual amounts could indicate kidney damage or dysfunction.

Full Blood Count (FBC) Test

Also known as a complete blood count (CBC), this is a common blood test that is often part of routine checkups. It measures the levels of different types of cells circulating in your bloodstream; specifically your red blood cells, platelets, and white blood cells. Some cancer treatments can affect the amount of these cells, which is why blood tests often play a role in monitoring your health during and after treatment. 

Abnormal levels of certain cells could indicate the presence of certain types of cancer, such as leukaemia and myeloma, or general health issues such as anaemia, infection, or clotting conditions. As there are many factors that can affect an FBC test, results have to be considered in combination with other information. 

Tumour Marker Or Biomarker Tests

Biomarkers or tumour markers are substances produced by cancer cells, or by the body in response to cancer. In the past, these have generally been proteins or other substances that cancer cells produce in higher amounts than normal cells. More recently the focus has shifted to gene markers related to mutations, expression patterns, and more, that come directly from the tumour or the tumour fragments in bodily fluids.

These tests are generally for patients diagnosed with cancer to find out more about their cancer, which can in turn guide treatment options or monitor treatment.

There are several tests that can fall under this category, one of them being circulating tumour cell tests. This measure can detect information about the cancer that is circulating in a patient’s blood and other fluids. This test is useful for certain types of cancer, including breast, colorectal, and prostate cancers. While it is not sensitive enough for diagnosis on its own, it can be useful in monitoring treatment progress, as well as after treatment to check for recurrence.

Liquid Biopsies

A biopsy is a medical procedure in which a small sample of tissue or cells is removed from a person's body for examination and analysis. There has recently been an exploration of the use of a single blood test to diagnose cancer. These tests are a type of biomarker test, which can identify cancer-specific DNA and cells that tumours shed into the bloodstream, and are sometimes referred to as a ‘liquid biopsy’. 

Several researchers and studies are evaluating the effectiveness of these tests, which not only offer a less invasive option compared to other biopsies, but they can also detect multiple types of cancer from a blood sample. While these tests have shown promising results, most of them are still being developed and validated, and are not yet widely available for clinical use.

Genetic Tests

Genetic testing involves checking for specific inherited mutations that are known to be involved in cancer susceptibility passed down in families.

Would Cancer Show On A Blood Test?

While blood tests can be useful in detecting cancer, they should not be relied upon as the sole method of diagnosis. Other diagnostic tests, such as imaging tests and biopsies, are necessary to confirm the presence of cancer and determine the extent of the disease. 

For example, if your doctor suspects that you have multiple myeloma, several blood tests could be done to measure the counts, as well as blood chemistry tests to assess kidney functioning, albumin and calcium levels, as these can all be affected in a patient with the disease. Results can give your doctor an indication of how advanced the disease is, and there are several other tests that they can also use for information such as urine tests, biopsies, and imaging.

Blood tests for cancer are constantly evolving, with ongoing research to improve their accuracy and reliability. As new diagnostic technologies and treatments are developed, blood tests may play an even more significant role in the early detection and management of cancer.

Patients should work with their healthcare providers to determine the appropriate diagnostic tests, screenings and treatment based on their individual medical history and risk factors.