The three most important characteristics of an ideal tumor marker are (a) it should be highly specific to a given tumor type, (b) it should provide a lead-time over clinical diagnosis and (c) it should be highly sensitive to avoid false positive results.
Each serum tumor marker has its own sensitivity and specificity. The sensitivity is the true positive rate in malignant cases, and the specificity is the true negative rate in benign cases.
Normal range: < 2.5 ng/ml. Normal range may vary somewhat depending on the brand of assay used. Levels > 10 ng/ml suggest extensive disease and levels > 20 ng/ml suggest metastatic disease.
An increase in tumour marker levels may mean the cancer is not responding to treatment, is growing or has come back (recurred). A slight increase may not be significant. The doctor looks at trends in the increase over time. Chemotherapy treatment can cause a temporary increase in tumour marker levels.
Tumor marker tests are not perfect. They are often not specific for cancer and may not be sensitive enough to pick up a cancer recurrence. The presence of tumor markers alone is not enough to diagnose cancer. You will probably need other tests to learn more about a possible cancer or recurrence.
Some of the tumor markers, such as prostate-specific antigen (PSA) and alpha-fetoprotein (AFP), are highly sensitive and specific, strongly correlating with the presence of a particular type of cancer.
Tumor markers can be present because of noncancerous conditions. People with cancer may never have elevated tumor markers in their blood. Even when tumor marker levels are high, they are not specific enough to confirm the presence of cancer.
There's a chance that a tumor marker test can give a “false positive.” That means the results suggest a person has cancer or that the cancer is growing, even when it's not. A tumor marker can also give a “false negative,” which means the results suggest a person doesn't have cancer when they actually do.
Stress hormones can inhibit a process called anoikis, which kills diseased cells and prevents them from spreading, Sood says. Chronic stress also increases the production of certain growth factors that increase your blood supply. This can speed the development of cancerous tumors, he adds.
Biomarkers are made by the cells, in response to different conditions [2]. They can basically be found in the fluids, such as blood or tissues [2]. Tumor markers are ideally used to diagnose cancer in people with no symptoms, and for early diagnosis, as well [3].
Tumor markers are most often used to track how your cancer is responding to treatment. If the level is going down, the treatment is working. If it goes up, the cancer may be growing. There are health issues other than cancer that can cause markers to be higher.
If tumor marker levels go down, it usually means your treatment is helping. Find any cancer that remains after treatment or cancer that comes back after treatment.
Cancer biomarkers can fluctuate over time, which means repeated testing may not give consistent results. In some patients, tumor marker levels don't go up until the cancer has gotten worse, which can make it harder to diagnose cancer or recurrent cancer in its early stages.
There are two main types of tumor markers: circulating tumor markers and tumor tissue markers. Circulating tumor markers can be found in the blood, urine, stool, or other bodily fluids of some patients with cancer. Circulating tumor markers are used to: estimate prognosis.
However, most cancers are not inherited and in the majority of cases people who are diagnosed with cancer do not have any of the “cancer genes” — at least none that we can currently identify. But all cancers do have biomarkers, including genetic biomarkers.
THE IDEAL BIOMARKER
It should be sensitive, but it should also correlate with the severity of damage. It should be accessible in the peripheral tissue; in the case of the kidney, for example, it should be measurable in either the blood or the urine.
The fact that only 5–10% of all cancer cases are due to genetic defects and that the remaining 90–95% are due to environment and lifestyle provides major opportunities for preventing cancer.
There is no single test that can diagnose cancer. So your doctor may start by asking about your personal and family medical history and doing a physical exam. They may order lab tests, imaging tests (scans), or other tests or procedures.
Clinical application of tumor markers can be broadly classified into 4 groups: Screening and early detection, diagnostic confirmation, prognosis and prediction of therapeutic response and monitoring disease and recurrence.
Some of the most promising include: HE4, mesothelin, M-CSF, osteopontin, kallikrein(s), and soluble EGF receptor.
Inflammation can affect tumor development and progression in addition to the response to therapy. Cytokines are mediators that govern a vast range of processes involved in the development of cancer, and markers of inflammation form a major part of the tumor microenvironment.
The hook effect (also known as high dose hook effect) is an artifact of tumor marker immunoassay kits, that causes the reported quantity of tumor marker to be incorrectly low when the quantity is high. An undetected hook effect may cause delayed recognition of a tumor.