Cancer is a disease that causes changes in cell genetic information, which in turn triggers uncontrollable cell growth and division. This finally leads to tumor formation and its metastases. Many cancers are very aggressive, so if the patient is not diagnosed and does not receive treatment in time, the disease can become incurable. Therefore, early cancer diagnosis is one of the most relevant topics in oncology.
Nearly all patients, doctors, and researchers dream of medical tests that might detect very early stages of the disease or its recurrences, and thus improve cancer prognosis as well as increase cure rates.
In today’s clinical practice cancer screening tests are used for early cancer detection. However, various pharmacy companies also offer newly developed multi-cancer early detection (MCED) tests, which, according to companies, from a single blood sample can detect two or three cancer types up to as many as 50.
Although pharmacy ads may sound exaggerated, and now widely used cancer screening tests are safe and reliable for use in the clinic, in some cases they are still unable to fully detect early cancer stages which in turn could likely be done by MCED tests.
Let’s take a deeper look at these diagnostic technologies.
Screening tests help to detect the possibility that a cancer is present before symptoms onset, ideally before metastasis. Most of the screening tests are routine tests used in cancer diagnostics, such as imaging, endoscopy, physical, laboratory (body fluids and tissues) testing, etc.
The main difference that in the case of cancer screening these tests are done once a doctor suspects that a patient has cancer or the person belongs to a special risk group (due to age, sex, family history, etc.), but does not have any symptoms yet.
If the patient has no symptoms, screening tests are usually prescribed by doctors according to screening programs. The American Cancer Society has provided cancer screening guidelines that are widely used.
Table 1 shows the list of the most common cancer types screening guidelines according to patient age.
Table 1. Cancer screening recommendations by age.
|Age Interval, Years||Recommended Screening|
|23-39||Cervical cancer screening (recommended for people with a cervix from 25 years)|
|40-49||Breast cancer screening (recommended from 45 years, with the option to begin at age 40) Cervical cancer screening (recommended for people with a cervix) Colorectal cancer screening (recommended for everyone from 45 years) Prostate cancer screening (recommended from 45 years for African Americans and people with close family members who had prostate cancer before age 65)|
|50+||Breast cancer screening |
Cervical cancer screening
Colorectal cancer screening
Lung cancer screening (for people who currently smoke or formerly smoked)
Prostate cancer screening
In the context of cancer screening, tumor markers are important.
Early detection of many types of cancers is performed by searching for specific substances (tumor markers) in patients' body fluids or suspicious tissues.
Two types of tumor markers can be distinguished: molecules which are produced and secreted to the patient organism by cancerous cells, and substances generated by the patient organism itself in response to cancer growth.
To the best of our knowledge, a very wide range of molecules can be assigned to tumor markers. Some of them are specific for one type of cancer, while others can be observed in several cancer types.
Additionally, there are many well-known markers that are detected not only in cancerous conditions but also in non-cancerous diseases or organism disbalances. These kinds of markers can provide misleading information and therefore are not used in clinics.
At the moment only single cancer screening tests are valid and used in clinical practice. Table 2 depicts common tumor markers currently in use.
Finally, if one of the screening tests gives a positive result the doctor usually does not consider it as definitive and prescribes additional examinations to fully confirm the diagnosis.
Multi-cancer early detection (MCED) tests
As science advances rapidly, pharmaceutical companies introduce newly developed MCED tests to the market. These tests, according to the companies, can detect multiple components of a growing cancer, such as circulating tumor cells, DNA, specific proteins and other analytes from a single blood sample. In other words, for early cancer detection MCED tests also use previously discussed tumor markers, but use them for more than one cancer detection at a time.
Despite the described MCED tests’ tremendous detection capabilities, much about them is still unknown. It is unclear if these tests are equally effective for various peoples (due to different genetic and epigenetic profiles), and whether their sensitivity varies by manufacturer or each cancer type, and etc.
Therefore, the US Food and Drug Administration (FDA) still hasn’t approved MCEDs as an early cancer diagnostic tool. However, some companies are offering MCEDs to doctors and patients as laboratory developed tests (LDTs, which are tests designed, manufactured, and used in only one laboratory), and the latter ones are not prohibited by FDA.
Still, it is believed that in the near future, MCED tests can be successfully implemented in real-clinical practice, just that more robust research is needed. It is now important to understand how best to maximize their benefits and minimize the potential harms.
With or without early detection testing, it is always a good idea to have regular checks by your doctor. Regular checks increase the probability of catching cancer or at least detecting some suspicious symptoms long before cancer is already spread throughout and thus increasing your chances of curing it.
Table 2. Most popular tumor markers are used for cancer screening
|Tumor Marker||Cancer Type||Sample Type|
|Alpha-fetoprotein (AFP)||Liver, ovarian, testicular||Blood|
|B-cell immunoglobulin gene rearrangement||B-cell lymphoma||Blood, bone marrow, tumor tissue|
|BCL2 gene rearrangement||Lymphomas, leukemias||Blood, bone marrow, tumor tissue|
|C-kit/CD117||Gastrointestinal stromal tumor, mucosal melanoma, acute myeloid leukemia, mast cell disease||Tumor tissue, blood, bone marrow|
|Calcitonin||Medullary thyroid carcinoma||Blood|
|CD19||B-cell lymphoma, leukemia||Blood, bone marrow|
|CD22||B-cell lymphoma, leukemia||Blood, bone marrow|
|Chromogranin A (CgA)||Neuroendocrine tumors||Blood|
|Cyclin D1 (CCND1) gene rearrangement or expression||Lymphoma, myeloma||Tumor tissue|
|Human chorionic gonadotropin (hCG)||Testicular, trophoblastic disease||Blood, urine|
|Monoclonal immunoglobulins||Multiple myeloma, Waldenström macroglobulinemia||Blood, urine|
|MYC gene expression||Lymphoma, leukemia||Tumor tissue|
|MYD88 gene mutation||Lymphoma, Waldenström macroglobulinemia||Tumor tissue|
|Neuron-specific enolase (NSE)||Small cell lung cancer, neuroblastoma||Blood|
|IRF4 gene rearrangement||Lymphoma||Tumor tissue|
|JAK2 gene mutation||Certain types of leukemia||Blood, bone marrow|
|PML/RARα fusion gene||Acute promyelocytic leukemia (APL)||Blood, bone marrow|
|Prostatic Acid Phosphatase (PAP)||Metastatic prostate cancer||Blood|
|Prostate specific antigen (PSA)||Prostate||Blood|
|T-cell receptor gene rearrangement||T-cell lymphoma||Bone marrow, tissue, body fluid, blood|
|Terminal transferase (TdT)||Leukemia, lymphoma||Tumor tissue, blood|
|Urine catecholamines: VMA and HVA||Neuroblastoma||Urine|
The earlier cancer can be detected, the greater the chance of survival and a cure.
Routine tests used in cancer diagnostics include imaging, endoscopy, physical, laboratory tests.
Various pharmacy companies also offer newly developed multi-cancer early detection (MCED) tests.
Tumor marker tests look for both the presence of tumors and the substances secreted by the tumors themselves.