The majority of CellSearch® images analyzed were from patients with M0 breast cancer, with <5 CTCs in their blood sample and from patients for whom blood sampling for CTC detection was performed before the administration of systemic treatment (Table 1).
Excluding the patients with breast cancer-related events before the sample collections, CTC detection was not significantly associated with disease-free survival/distant-disease-free survival, in contrast to DTC detection [ 17].
Blood samples were subjected to CTC detection assay, and then detectable cells were counted by fluorescence microscopy.
To demonstrate the feasibility of CTC detection in patient blood, duplicate blood samples were drawn from 45 metastatic breast cancer patients for analysis by CTCscope and the CellSearch system.
Further trials should therefore evaluate the clinical value of DTC/CTC enumeration in the neoadjuvant situation, especially as CTC detection offers the possibility of serial blood sampling during the course of therapy.
In the 49 patient samples with CTC counts in the range of one to four, our method showed a significantly higher CTC detection rate (p < 0.01) and a larger CTC detection range than that of the CellSearch™ method.
CTC detection in vivo is a big challenge and can sample a much larger volume of blood compared to patient blood draws.
To determine the specificity of CTC detection, peripheral blood was obtained from ten healthy donors and samples were also processed as described above.
The anti-CK antibody-based CTC-enrichment method uses an intracellular CK protein marker to enrich CTCs and achieve better sensitivity of CTC detection than that of the surface EpCAM protein marker in blood samples from breast cancer patients.
This model allowed taking into account the major challenges for CTC detection and enumeration: (1) the discrete process; (2) the Poisson-distributed sampling error; (3) the overdispersion; and (4) the high number of CTC counts equal to 0. This report represents the first use of a cell lifespan model to describe CTC kinetics.
Serial testing of RT-PCR-based CTC detection protocols (whereby detection of all markers tested is required to designate a sample as CTC+) may thus improve specificity while parallel testing, considered positive if any of the markers is detected, may increase sensitivity.
