Circulating tumor cells (CTCs) are identified in 20%–25% of patients with nonmetastatic breast cancer, and recent research suggests that detection of CTCs at five-year follow-up may predict late recurrence for nonmetastatic, estrogen receptor-positive (ER+), human epidermal growth factor receptor 2-negative (HER2–) breast cancer. In a study presented at the San Antonio Breast Cancer Symposium on December 6, 2018, researchers from the University of Texas MD Anderson Cancer Center found that the presence of CTCs in patients with nonmetastatic breast cancer was associated with shortened relapse-free survival (RFS), regardless of the subtype.

Prior to surgical resection, 506 patients (mean age = 53 years) with nonmetastatic breast cancer underwent CTC enumeration. Researchers used the Cell SearchSystem to identify CTCs per 7.5 ml of blood. The presence of one or more CTC met the morphologic criteria for malignancy. Patients were followed for a median of 68 months.

Most patients (n = 417) had T1/T2 tumors, 307 had grade 1 or 2 tumors, and 292 had negative lymph nodes. The majority of patients (n = 419) had ER+/HER2– disease, whereas 87 had triple-negative disease.

Researchers discovered one or more CTCs in 91 patients with ER+/HER2– disease and 24 patients with triple-negative disease. Among all patients, 45 had recurrent disease within five years of CTC assessment, and the presence of CTCs was associated with shortened RFS: median RFS was 1.2 years for CTC-positive patients compared to 2.5 years for CTC-negative patients. The correlation remained regardless of disease subtype (hazard ratio = 2.71; 95% confidence interval = 1.50–4.87; p < 0.001).

“These data warrant larger studies to determine if CTC positivity can be used to stratify both ER+ and triple-negative patients who are at increased risk for early recurrence,” the researchers concluded.