Tumor marker

A tumor marker is a substance produced by a tumor or by the host in response to a tumor that is used to differentiate a tumor from normal tissue or to determine the presence of a tumor based on measurements in the blood or secretions. Such substances are found in cells, tissue, or body fluids and are measured qualitatively or quantitatively by chemical, immunological, or molecular biological methods. 

Some tumor markers are specific for one type of cancer, and others are seen in several cancer types. Many of the well-known markers are seen in noncancerous conditions and cancer. Consequently, these tmnor markers are not diagnostic for cancer. However, it is thought that the blood levels of tumor markers reflect tumor activity and volume. 

Stomach, liver, pancreas Colon, stomach, pancreas Gerinmal tumors Adrenal 

Modified from Sell S. Cancer markers. In Moossa AR Schempff SC, Robson MC, eds. Comprehensive textbook of oncology, 2nd ed, Vbl. 1. Baltimore Williams Willdns, 1991 225-38. 

Carcinoembryonic antigen AFP, alpha fetoprotein hCG, human chorionic gonadotropin. 

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Hepatocellular carcinoma (HCC) develops in patients with chronic liver diseases associated with hepatitis B and hepatitis C vims infections with high incidences. Here, an acyclic retinoid has been shown to suppress the posttherapeutic recurrence after interferon-y or glycerrhicin treatment in cirrhotic patients who underwent curative treatment of preceding tumors. The retinoid induced the disappearance of serum lectin-reactive a-fetoprotein (AFP-L3), a tumor marker indicating the presence of unrecognizable tumors in the remnant liver, suggesting a deletion of such minute (pre)malignant clones (clonal deletion). As a molecular mechanism of the clonal deletion, a novel mechanism of... 

Serum cancer antigen 125 (CA-125) is the most extensively evaluated tumor marker for ovarian cancer. Unfortunately, the CA-125 determination is non-specific, and elevated levels can be associated with a number of other gynecologic and gastrointestinal diseases. CA-125 levels in a woman without ovarian cancer, though, are static or tend to decrease over time, whereas levels associated with malignancy will continue to rise.10 Since CA-125 is a non-specific marker, there is no standard recommendation for routine screening for prevention of ovarian cancer. 

Flow cytometry A method of measuring the number of cells in a sample, the percentage of five cells in a sample, and certain characteristics of cells, such as size, shape, and the presence of tumor markers on the cell surface. The cells are stained with a light-sensitive dye, placed in a fluid, and passed in a stream before a laser or other type of light. The measurements are based on how the light-sensitive dye reacts to the light. 

Tumor markers are tumor-associated analytes that are used in patients with known malignancy (carcinoma, sarcoma, lymphoma, etc., which have been diagnosed and confirmed by biopsy). Tumor marker in vitro diagnostic (IVD) tests are... 

The premarket notification application, 510(k), is reviewed by the FDA scientific staff. This evaluation takes into consideration tumor-associated analytes, test requirements, medical usefulness of the test system for a particular clinical claim, and its application (i.e., monitoring or treatment follow-up). The FDA determines the appropriate performance requirements for each tumor analyte category. The agency s staff considers factors, such as consequences of a false positive or false negative, and the importance or impact of an absolute versus a significant change in the results or values of the tumor marker tests. The performance criteria (parameters) of a particular tumor marker test are compared with those of previously... 

The establishment of performance criteria for a given tumor marker test is not a simple process because accuracy and precision are unique for each type of analyte and its application. Establishing methodological limits for accuracy, precision, sensitivity, and specificity often requires standard reference materials, quality control materials, comparative studies, and actual clinical specimens. Accuracy and precision must be measured over the analyte reportable range for which the device is intended to be used. Sensitivity and specificity must be considered with respect to the intended clinical use of the device. Also, the indications for use should be carefully considered in the design of the study protocol. The indications for class II should be to monitor residual tumor after surgery (or radiation), the recurrence of tumor, or response to therapy. A 510(k) must provide clear evidence that the device is accurate, safe, effective, and substantially equivalent to a device legally marketed in the United States. 

The FDA evaluates each tumor marker test against its own labeling claims as to how well it performs and compares it with other cleared and marketed devices identified in the 510(k) submission. The intended use claim for monitoring must be supported by valid scientific and clinical data. Labeling a tumor marker test for a particular claim can mean that the testing system may have to show supporting data for that claim. For example, a tumor marker proposed for a monitoring claim will require laboratory and clinical data to support that claim (4,5). 

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