Key Takeaways

• Cancer is generally easier to treat in its earlier stages. However, the disease often doesn’t cause any noticeable symptoms at this point.

• Screening tests that detect cancer can help to detect it early, even before any symptoms are apparent. This allows for more treatment options and improves the likelihood of long-term survival.

• Blood tests can look for DNA fragments in the blood that are produced by cancer cells. This can be used to screen for multiple different types of cancer at once.

• Certain types of cancer produce specific proteins or other substances that may be detectable in the blood, which are known as tumour markers. A few tumour markers may be useful for screening.

• A complete blood count (CBC) is a routine blood test that’s generally included as part of a standard health screening. This can detect certain types of cancer, including leukemia and lymphoma.

• Other conditions may also cause a positive test result, so a screening test is not used for diagnosis on its own.

• If a screening test finds evidence of cancer, it will be necessary to perform additional testing to be sure of the diagnosis. 

Importance of screening for cancer

When cancer is detected in its early stages, it’s much easier to treat. An early-stage cancer is generally contained to one part of the body, and may even be able to be treated with surgery alone. When cancer has spread more widely around the body, chemotherapy is likely to be required. Early-stage cancers also have significantly better survival rates, meaning that you’re more likely to live for a long time after diagnosis than if the cancer is detected at a later stage.

However, many cancers don’t tend to cause obvious symptoms in their early stages. By the time there are clear symptoms of cancer, it’s likely that it will have already progressed to a later stage, and treatment will be more difficult. 

This is why screening tests for cancer are useful. By checking for cancer even when there are no symptoms, it’s more likely that cancer will be detected early, which allows for more treatment options and a better chance of long-term survival.

Can blood tests detect cancer?

There are various methods of checking for cancers. In some cases, imaging of a particular tissue is used. An example of this is a mammogram, which is an X-ray of the breast that’s used to check for breast cancer. This can detect small tumors, and may be able to detect cancer even while it’s still microscopic. However, this type of screening is not possible for all cancers.

For years, researchers have been searching for a way to detect cancer on a blood test. This would make it easier to screen large numbers of people for cancer in a non-invasive manner, so that more cases of cancer can be detected early and treated. The dream of a blood test that reliably detects all types of cancer has not quite been realized, but we’re getting closer. We already have a few different blood tests that may be useful for cancer screening.

DNA fragment detection (liquid biopsy) for early detection of cancer

In order to become cancerous, a cell first experiences one or more changes in its DNA. This is the genetic information that controls how the cell behaves. Once these DNA changes have occurred, then the cell may begin to divide out of control, which causes it to become cancerous.

A blood test can look for abnormal DNA fragments in the blood that are associated with cancer. With new developments in biotechnology, it’s possible to detect very small amounts of DNA. This is sometimes known as a “liquid biopsy,” because it checks for cancer cells in much the same way that a biopsy does. However, instead of taking out a small piece of tissue surgically, the liquid biopsy uses a blood test. DNA fragments are released from cancer cells into the bloodstream, making it possible to detect many different types of cancer with a single blood test.

So far, the only DNA fragment detection test on the market is the LucenceINSIGHT test. There are tests available that check for specific abnormal DNA markers that are associated with specific types of cancer. The standard LucenceINSIGHT test checks for 12 different types of cancer, including:

• Breast cancer

• Lung cancer (both small cell and non small cell lung cancers)

• Lung neuroendocrine tumors

• Nasopharyngeal cancer

• Liver cancer

• Biliary tract cancer

• Cervical cancer

• Gastrointestinal stromal tumor (GIST)

• Pancreatic cancer

• Colorectal cancer

• Prostate cancer

A more extensive test known as LucenceINSIGHT Plus checks for 50 different types of cancer. In addition to the cancers listed above, this test also checks for:

• Thyroid cancer

• Esophageal cancer

• Eye cancer

• Oropharyngeal cancer

• Laryngeal cancer

• Salivary gland cancer

• Non Hodgkin lymphoma

• Hairy cell leukemia

• Acute myeloid leukemia

• Mast cell tumor

• Myeloproliferative neoplasms

• Myeloma

• Kidney cancer

• Adult Wilms tumor

• Adrenal gland cancer

• Stomach cancer

• Stomach neuroendocrine tumors

• Small intestine cancer

• Colorectal neuroendocrine tumors

• Bladder cancer

• Endometrial cancer

• Ovarian cancer

• Ovarian germ cell and stromal tumors

• Vulvar cancer

• Penile cancer

• Testis cancer

• Soft tissue cancer

• Bone cancer

• Skin cancer

If abnormal DNA fragments are found, then further medical testing will be needed to look for evidence of cancer. The LucenceINSIGHT test reports where the cancer is likely to be found, so that doctors can target their investigations. In about 1% of cases where abnormal DNA fragments are detected, cancer is not found. This could mean that it was a false positive result and that there truly is no cancer, or that the cancer is not yet at a point where medical testing can locate it. Although this is uncommon, it’s important to be prepared for the possibility.

This test is able to detect very small amounts of abnormal DNA in the blood, but it’s not able to detect every case of cancer. About 81% of cases of cancer are detected by the liquid biopsy test. The test can provide peace of mind, but cannot completely rule out the possibility that you have a few cancer cells somewhere in your body, which could later develop into a tumor. Repeating the test helps to confirm the result.

This type of testing may be recommended for people over the age of 40, who are at a higher risk for many different types of cancer. It may also be recommended for those whose cancer risk is higher due to family history or lifestyle factors (such as smoking or dietary factors). If you believe that this testing might be beneficial for you, talk with a qualified healthcare professional to discuss the pros and cons of testing. You will need a doctor’s prescription in order to receive the test.

Another blood test, known as GastroClear, detects small amounts of abnormal RNA. RNA is also a type of genetic material, and is used by cells to carry genetic information from the DNA into the other parts of the cell. GastroClear is designed to look specifically for abnormal RNA sequences associated with stomach cancer. This test may be recommended for people who are at a higher risk for stomach cancer, due to their lifestyle, medical history, or family history.

Tumour marker blood tests to detect cancer

Cancer cells often make specific proteins or other substances at higher rates than healthy cells do. These substances can be detected in the blood, and are known as tumour markers.

Tumour markers are commonly used to follow a cancer patient’s progress during their treatment or to check for a recurrence of cancer. In addition, they can be useful to diagnose a specific type of cancer when the origin of a patient’s cancer is unclear. However, some tumour markers are also being used for screening.

Some common tumour markers include:

• CA 19-9, which is associated with pancreatic cancer

• CA 125, which is associated with ovarian cancer

• CA 15-3, which is associated with breast cancer

• Prostate specific antigen (PSA), which is associated with prostate cancer

• Carcinoembryonic antigen (CEA), which is associated with a variety of different cancers

• Alpha fetoprotein (AFP), which is associated with ovarian, testicular, and liver cancer

Unfortunately, research on screening with tumour markers has found that these tests miss many cases of cancer, so they may not always be useful as screening tests. However, some tumour markers may be used for screening in certain situations.

For example, prostate specific antigen (PSA) is found at higher levels in the blood of men with prostate cancer. However, other conditions can also cause PSA to be elevated, and research has found that around 70% of men with high PSA levels do not have prostate cancer. In addition, some men with prostate cancer have normal PSA levels. Because of this, PSA is not a perfect screening test for prostate cancer, but it may be useful for some men.

The Ministry of Health doesn’t currently recommend that all men have PSA as a screening test, but some men may choose to have this test to check for prostate cancer, particularly if they’re at a higher risk for this condition. Discuss the risks and benefits with your doctor to decide whether PSA testing makes sense for you. 

In fact, the Ministry of Health does not recommend using any tumour marker tests to screen for cancer. This is because, in general, these tests have not been shown to be accurate enough to be worthwhile.

Complete blood count (CBC) to detect cancer

Certain cancers can also be detected with a routine blood test known as a complete blood count (CBC). This test checks the numbers and types of blood cells, including red blood cells, white blood cells, and platelets. A CBC is routinely included as part of a standard health screening, and this test is also very commonly ordered to diagnose or follow up on many different medical conditions.

Certain cancers, including leukemia and lymphoma, can cause a high white blood cell count, which will be seen on a CBC. White blood cells are the cells of the immune system that fight infection. A high white blood cell count doesn’t always indicate cancer – other common conditions, such as a bacterial or viral infection, can also cause a high white blood cell count. If your white blood cell count is high, then additional testing will be needed to determine whether this represents cancer or another condition.

Many types of cancer can spread to the bone marrow, even if they originate in a distant location. Because the various types of blood cells are made in the bone marrow, cancer that’s growing in the bone marrow can reduce the numbers of all of the types of blood cells, which would be detected on a CBC. This would generally indicate a later stage of cancer, and it’s likely that symptoms would be experienced by this point.

Additional testing after a positive cancer screening test

If you test positive on any cancer screening blood test, this means that the test has found evidence that you might have cancer. However, this doesn’t always mean that you have cancer. In many cases, other conditions can also cause a positive test. Screening tests are not used to diagnose cancer on their own. You’ll need follow-up testing to determine whether you have cancer.

The interpretation of cancer screening blood test results is complex. This is why these tests are only offered with the prescription of a doctor. You’ll need a medical professional to help you determine which screening tests would be beneficial for you, interpret what the results mean, and decide on the next steps if the test is positive. 

Besides blood tests, there are also multiple other ways to screen for cancer. These include imaging tests (such as mammograms for breast cancer and low dose lung CT scans for lung cancer), stool testing (such as the fecal occult blood test for colorectal cancer), and cell sampling (such as Pap smears for cervical cancer). Many of these screening tests are recommended by the Ministry of Health for those in certain age groups or who have other cancer risk factors, because scientific evidence has shown that their use is beneficial. Your doctor will advise you on which screening tests would be recommended for you, based on your age, lifestyle, medical history, and family history.