Cryopreservation for delayed circulating tumor cell isolation is a valid strategy for prognostic association of circulating tumor cells in gastroesophageal cancer

Figure 1 Representative images of circulating tumor cell isolation from fresh and cryopreserved samples demonstrating preservation of leukocyte and circulating tumor cell morphology. The fresh sample demonstrates a nucleated CK+/CD45- CTC which is uPAR negative, as well as a CK-/CD45+ leukocyte. The cryopreserved sample shows a uPAR positive CTC. CTC: Circulating tumor cell.

Figure 2 Circulating tumor cell enumeration by processing method. Mean number of CTCs isolated in the fresh specimens were higher than in the matched cryopreserved sample (mean difference in CTCs 17.1 95%CI: 0.7-33.6, P = 0.043). This difference was mostly driven by larger falls in CTC counts in samples with high numbers of CTCs (> 50 CTCs in fresh samples), with no significant difference in CTC counts for samples with less than 50 CTC in the fresh specimen (P = 0.06).

Figure 3 Circulating tumor cell count by stage. CTC processing post cryopreservation produced a higher mean CTC count in metastatic patients compared to the resectable patients (mean CTC in metastatic 53.8 vs resectable 15.8, P = 0.0013). CTC: Circulating tumor cell.

Figure 4 Overall survival by circulating tumor cell count. Patients with > 17 CTCs isolated from cryopreserved specimens had a poorer overall survival compared to those with ≤ 17 CTCs (median OS 2.8 mo vs 23.2 mo, HR = 4.4, 95%CI: 1.7-11.7, P = 0.0013). OS: Overall survival; CTC: Circulating tumor cell.