Analysis of disseminated tumor cells (DTCs) in primary breast cancer patients with various molecular subtypes.

Abstract

e13000 Background: Despite successful treatment of the primary tumor, recurrence occurs in about 30% of breast cancer patients. One reason might be hematogenous spread during early disease stages. Disseminated breast cancer cells (DTCs) preferentially migrate into the bone marrow (BM) at early stages of the disease. Due to low proliferation, DTCs are persistent against systemic chemotherapy and might cause metastatic relapse at a later stage. Methods: BM aspirates were collected from the anterior iliac crest of patients with primary mamma carcinoma during surgery. After density gradient centrifugation cell suspensions were transferred onto glass slides and subjected to immunocytochemical staining against pan-cytokeratin. DTCs were visualized in pink using alkaline phosphatase and short counterstaining with hematoxylin which colored the nuclei light blue. DTCs were semi-automatically detected and enumerated using the Aperio Versa microscope based scanning system with a rare events algorithm that was trained to identify DTC candidates according to color, shape, intensity and size. As a positive control with each run, we used reference slides with a mix of bone marrow cells and a defined number of HCT116 cells. Results: Between February 2019 and December 2020 BM aspirates from 158 primary breast cancer patients were collected. Per patient about 4 million BM cells were analyzed. DTC detection revealed a positivity rate of 29% (46 patients). Molecular subtype analysis of DTC positive patients showed that 37% of the primary tumors (17 patients) were luminal A and 37% (17 patients) luminal B. In 9% of the cases (4 patients), tumors were HER2 enriched and 15% (8 patients) were triple negative. DTC count indicated that the majority of luminal B patients had 11-20 DTCs whereas luminal A patients tended to have lower DTC quantities varying between 1 and 10 DTCs. Conclusions: DTCs may serve as independent prognostic markers. Follow-Up data might reveal whether DTC quantification and molecular subtypes at primary diagnosis can be used to stratify patients at elevated risk for recurrence.