Impact of Sensitive Circulating Tumor DNA Monitoring on CT Scan Intervals During Postoperative Colorectal Cancer...

This study investigated whether digital polymerase chain reaction (dPCR)-based circulating tumor DNA (ctDNA) monitoring can allow longer intervals between computed tomography (CT) scans during postoperative surveillance of colorectal cancer (CRC).

Practical guidelines still recommend intensive postoperative surveillance of CRC using periodical CT scans and serum carcinoembryonic antigen testing.

The longitudinal dynamics of ctDNA for 52 patients with CRC as measured by dPCR using probes targeting 87 individual tumor-specific mutations (1-5 per patient) were compared with results from conventional (ie, clinical) surveillance using serum tumor markers and CT.

A total of 382 CT procedures were carried out for the patient cohort (3.3/year per patient) and the median lead time from ctDNA relapse to clinical relapse was 182 days (range, 0-376 days). If the CT interval was annual, potential delays in the detection of clinical relapse would have occurred for 7 of the 10 patients who experienced clinical relapse (9 of 13 events), with a median delay of 164 days (range, 0-267 days). If annual CT surveillance was performed together with ctDNA monitoring, 218 (57.1%) CTs would not have been needed to detect the first clinical relapse. In addition, the ctDNA monitoring would have provided a lead time of 339 days for detection of clinical relapse (range, 42-533 days).

Our findings suggest that the ctDNA monitoring as part of postoperative surveillance and clinical relapse detection for patients with CRC could allow the CT interval to be lengthened.

This trial was registered with University Hospital Medical Information Network Clinical Trial Registry (UMIN000045114).