Combined Analysis of Disseminated Tumor Cells (DTCs) and Circulating Tumor DNA (ctDNA) in a Patient Suffering from Triple Negative Breast Cancer Revealed Elevated Risk

Background: Disseminated tumor cells (DTCs) in bone marrow aspirates of patients with primary breast cancer may serve as independent prognostic markers associated with impaired survival. Due to limited therapy options and high risk of recurrence particularly, women diagnosed with the aggressive triple negative breast cancer (TNBC) require personalized treatment choices. Genetic profiling of circulating cell-free tumor DNA (ctDNA) might help to find individual treatment options and to monitor disease course. Methods: Here we report the case of a 66-year-old patient with TNBC. She received neoadjuvant chemotherapy (NACT) that had to be interrupted due to intolerance. Surgical resection of the residual tumor resulted in pathologic complete response (pCR), though. Results: Bone marrow aspiration during surgery revealed an unusual high number of DTCs and thus elevated risk for recurrence. Analysis of pre-surgical blood and urine samples revealed the presence of plasma-derived and urinary ctDNA after NACT and indicated poor prognosis. Subsequent targeted sequencing showed that pathogenic variants occurred in urinary and plasma-derived ctDNA emphasizing the potential of liquid biopsy usage for early detection of relapse. Despite the detection of residual molecular disease after NACT, the presented patient reached pCR and could benefit from standard treatment until present. Conclusions: In this case, liquid biopsy based biomarkers did not necessarily correlate to clinical outcome. Further, ctDNA analysis did not reveal approved therapeutic options to target the identified pathogenic variants. Adjuvant bisphosphonate treatment was applied based on the positive DTC status and may improve the patients' prognosis. Further investigations are required to identify TNBC patients at risk for recurrence.