Immunocytochemistry staining for ER and PR in circulating tumor cells as compared to primary tumor or metastatic biopsy.

Abstract

584 Background: Hormone receptor (estrogen receptor [ER] and progesterone receptor [PR]) status in all breast cancer patients is recommended for selection of treatment options. However, the analytical sensitivity of immunohistochemistry (IHC) in detecting low levels of ER/PR is often poor and is likely due to methodological variation. Because biopsy is not often feasible in all patients with recurrent and/or metastatic breast disease, circulating tumor cells (CTCs) offer an attractive alternative source of tumor tissue for determining ER/PR status and can be monitored more readily to enable a more effective course of treatment. Methods: Twenty mL of peripheral blood was collected prospectively from 15 patients diagnosed with late stage metastatic/recurrent breast cancer. CTCs were isolated using the microfluidic OncoCEE platform. A cocktail of antibodies was utilized for CTC capture and detection with an expanded anti-cytokeratin (CK) cocktail mixture and anti-CD45. ER/PR protein expression was assessed by immunocytochemistry (ICC) on the cells captured within the microchannels and compared to IHC performed on the primary tumor or metastatic biopsy. Results: CK+/CD45-/DAPI+ cells were located and assessed for ER/PR ICC. Among the 15 cases, a high concordance (13/15; 87%) in ER/PR status between IHC and ICC results was observed. Two cases were found to be discordant where one was positive by IHC and negative on the CTCs, and the other was negative by IHC and positive on the CTCs. However, both cases that were discordant had low numbers of detected CTCs. Conclusions: There is significant heterogeneity between ER/PR protein expression in CTCs and primary tumor/metastatic biopsy, and this status may change over time due to therapy. ER/PR ICC on CTCs from peripheral blood using the OncoCEE platform is shown to be feasible with high concordance (87%) in ER/PR status between primary tumor/metastatic biopsy (by IHC) and CTCs (by ICC). The significance of heterogeneity at the ER/PR protein level in CTCs ascertaining to the prognosis and predictive response to anti-estrogen therapy needs further evaluation in larger prospective clinical trials.

Circulating tumor cell assay to non-invasively evaluate PD-L1 and other therapeutic targets in multiple cancers

“…With our test, we show sensitivity of 83%, 80% and 63% and specificity of 89%, 94%, 89% for ER, PR, HER2 respectively on CTCs derived from known cancer patients. Studies have reported significant heterogeneity between ER/PR/HER2 protein expression in CTCs and primary tumor/metastatic biopsy, and this status may change over time due to therapy [11,[42][43][44][45]. In our CTC-based test, we observed slightly lower sensitivity for HER2 by ICC than other markers.…”