DNA alterations in the plasma and serum of cancer patients: A molecular tumor marker

Conventional serum tumor markers are soluble glycoproteins that have proven clinically useful for the initial diagnosis as well as the follow-up in mu ltiple tumor entities. However, a number of tumors lack known tumor markers or the tumor markers are characterized by either low sensitivity or specif icity. The detection of disseminated tumor cells in the blood by reverse tr anscriptase polymerase chain reaction (RT-PCR) techniques has offered a bro adened spectrum of minimally invasive tumor detection. However, these proce dures are laborious and costly. Recently, microsatellite analysis, a PCR-ba sed method for detection of tumor-specific DNA alterations, identified tumo r DNA in the plasma and serum of cancer patients. According to the literatu re, the specificity of this procedure equals 100% because controls did not exhibit microsatellite alterations in their plasma or serum DNA. Non-cell-b ound, free tumor DNA in the plasma or serum can be identified just as well by detection of other genetic or epigenetic DNA alterations, such as mutati ons or DNA methylation differences. This article summarizes the current lit erature on the detection of tumor DNA in the plasma and serum of cancer pat ients, including own data obtained from patients with clear cell renal carc inoma. The potential clinical value of such molecular tumor markers for the initial diagnosis and the follow-up of cancer patients will be discussed.