Circulating cell-free DNA in plasma of locally advanced rectal cancer patients undergoing preoperative chemoradiation: a potential diagnostic tool for therapy monitoring.

Circulating cell-free DNA opens up an interesting field for therapy monitoring, in particular during multimodal therapy protocols. The objective of this proof of principle study was to evaluate whether the amount of circulating plasma DNA has the potential to serve as a marker for therapy monitoring during the treatment course of locally advanced rectal cancer patients. We especially focused on kinetics of circulating DNA to assess whether variances in kinetics have the potential to discriminate between therapy responders and nonresponders. The amount of circulating DNA in plasma of rectal cancer patients undergoing preoperative chemoradiation was determined using real-time PCR before chemoradiation, after the end of chemoradiation and at the end of treatment. The study population was divided into responders (ypT0-T2 stage) and nonresponders (ypT3-T4 stage). Both groups showed comparable median plasma DNA values before and after the end of chemoradiation. At the end of treatment responders showed a further decrease in circulating DNA, whereas in nonresponders the circulating DNA manifestly increased (P = 0.006). This study demonstrates that circulating DNA in plasma of rectal cancer patients undergoing preoperative chemoradiation might serve as a surrogate marker to discriminate between responders and nonresponders. Therefore, we hypothesize that quantification of plasma DNA could be of use as an easily accessible tool for therapy monitoring in these patients.

Disseminated tumor cells in peripheral blood: a novel marker for therapy response in locally advanced rectal cancer patients undergoing preoperative chemoradiation.

PURPOSE: This study was designed to examine whether disseminated tumor cells in peripheral blood of locally advanced rectal cancer patients undergoing preoperative chemoradiation have the potential to serve as a marker for therapy response. Studies suggest that patients with advanced rectal cancer who respond to preoperative chemoradiation most likely benefit from this treatment. METHODS: From advanced rectal cancer patients undergoing preoperative chemoradiation, peripheral blood was obtained at defined times: before, during, and after chemoradiation and during surgery. Patients were divided into histopathologic responders (ypT0-T2) and nonresponders (ypT3-T4). Cytokeratin 20 and carcinoembryonic antigen reverse transcriptase-polymerase chain reaction were performed to detect disseminated tumor cells. A blood sample was deemed positive for disseminated tumor cells if both carcinoembryonic antigen and cytokeratin 20 were detected. RESULTS: The overall population (n = 26) showed a positivity rate of 32 percent for disseminated tumor cells before initiation of chemoradiation. Of the responders (n = 8), 63 percent were positive for disseminated tumor cells before chemoradiation, whereas only 18 percent of nonresponders (n = 18) were positive (P = 0.026). From initiation of chemoradiation to the end of surgery, a significant decrease was seen in tumor cell positivity in the blood of responders (P = 0.042). Moreover, the responders represented a trend toward a decrease in tumor cell positivity during chemoradiation (P = 0.079). In contrast, there were no noticeable alterations within the treatment course in nonresponders. CONCLUSIONS: This prospective proof of principle study demonstrates that locally advanced rectal cancer with preoperative chemoradiation shows different biologic behavior in terms of tumor cell dissemination in peripheral blood when therapy responders compared with nonresponders.