The influence of removal of primary tumor on incidence and phenotype of circulating tumor cells in primary breast cancer

Recent studies have shown that the detection of circulating tumor cells (CTC) pre and postoperatively in the peripheral blood of primary breast cancer patients may be an indicator for poor survival. This study aimed to investigate the influence of removal of the primary tumor on incidence and phenotype of circulating tumor cells in primary breast cancer. 209 primary breast cancer patients could be included into this analysis. Blood sampling was performed both pre and postoperatively. The blood specimens were immunomagnetically enriched using AdnaTest BreastCancerSelect within 4 h after blood withdrawal, followed by RNA isolation and subsequent gene expression analysis by reverse transcription and multiplex PCR using AdnaTest BreastCancerDetect. Three breast cancer-associated tumor markers and two hormone receptor genes were amplified: GA733-2, Muc-1, Her-2, ER, PR. In addition, bone marrow (BM) status was intraoperatively determined. Forty-three of 209 patients (21%) had pre and/or postoperatively circulating tumor cells. The positivity rates after surgery were higher but did not differ significantly (12% pre and 16% postoperatively, P = 0.264). Disseminated tumor cells in BM were seen in 32 of 209 cases (15%). Patients with positive BM status had significantly higher CTC positivity rates both pre and postoperatively compared to those with negative BM status. The most common CTC phenotype was triple negative (24 patients) followed by HER2+/ER-/PR- subtype (10) and ER and/or PR positive (9). Interestingly, 41 of 43 primary tumors (95%) were ER and PR positive. Removal of the primary tumor did not alter the phenotype of CTC. Surgery does not significantly influence the tumor cell load in the blood stream. CTC phenotype before and after the surgery generally remains identical but may differ from that of the primary tumor.