Improvement of specific detection of circulating tumor cells using combined CD45 staining and fluorescence in situ hybridization

Background: Conventional cytokeratin (CK)-based methods to detect circulating tumor cells (CTCs) often present suboptimal sensitivities for decreased or non-expression of cytokeratin in some CTCs. We clinically investigated a new method that combines immunocytochemistry staining (ICC) of CD45 and fluorescence in situ hybridization (FISH).

Methods: Circulating epithelial cells from 141 subjects were enriched using an EpCAM-independent strategy and then identified by either a combination of FISH with chromosome 8 centromere probe (CEP8) and ICC staining of CD45 (CD45-FISH) or ICC staining of CK.

Results: For detecting CTCs enriched from lung cancers, CD45-FISH had larger areas under ROC curves of 0.963 (P=0.000) compared to ICC (0.653; P=0.031) using cut-off values of 2 and 1 cell/3.75ml blood with sensitivities of 83.3% and 43.3%, specificities of 98.6% and 89.5%, respectively. Moreover, CD45-FISH showed 76.2% sensitivity in detecting CTCs in ovarian cancers (P<0.001). Four of six ovarian cancers showed dramatical decrease in both CTCs and serum CA125 on the 7th day after surgery.

Conclusion: CD45-FISH method had improved sensitivity and specificity in detecting CTCs of lung and ovarian cancers compared to ICC-CK. This combined detection strategy may be useful in detecting or monitoring CTCs after ovarian cancer surgery.