Concordance of HER2 status between primary tumor and circulating tumor cells in breast cancer.

Background: During tumor progression, HER2 expression undergoes dynamic changes. Circulating tumor cells (CTCs) can be used to monitor HER2 expression in real-time and hold potential for clinical application. This study aimed to evaluate the consistency of HER2 expression between primary tumors and CTCs in patients with breast cancer (BC).

Methods: We used a previously established telomerase reverse transcriptase-based CTC detection method (TBCD) combined with anti-HER2 antibody to detect CTC and HER2-positive CTC (HER2 + CTC) in 4 ml of peripheral blood from patients with breast cancer prior to radiotherapy. The results indicated that the status of HER2 in CTC was inconsistent with the histological results.

Results: Discordance in HER2 status between primary tumor and CTC was observed in 32.6% of patients (kappa value = 0.325, p = 0.03). And among patients with histologically HER2-negative breast cancer, the detection rate of HER2 + CTC was 32.1% (9/28).

Conclusions: We found that the HER2 status of CTC in peripheral blood was inconsistent with the histological findings. Further research should explore the clinical significance of detecting HER2-positive CTCs, and it is desired that real-time HER2 status testing of CTCs could hold potential value for patients with breast cancer.