Title: Impact of circulating tumor DNA (ctDNA) surveillance for patients with early-stage breast cancer: A multi-institution real-world analysis.

Author: Kasey Fitzsimmons

Area of Concentration: Breast Cancer

Specialty: Oncology

Keywords: Breast Cancer, Circulating Tumor DNA, Signatera

Objective: To investigate the landscape of currently targetable genomic alterations in tumors from 1,501 patients with early-stage (stage I-III) hormone positive breast cancer who had ctDNA testing in the real-world setting.

Background:

Detection of minimal residual disease (MRD) via ctDNA in the adjuvant setting of early breast cancer (EBC) is strongly associated with recurrence. However, surveillance testing and/or imaging are not performed routinely in this setting because the clinical impact of early detection and potential intervention remains unclear. In this multi-institution analysis, we investigated the impact of ctDNA detection in the adjuvant setting on patient care.

Methods: We included participants receiving care at four institutions that had MRD testing via Signatera Residual Disease Test after EBC surgery. Results were obtained by retrospective review of electronic medical records. 

Results:

464 patients with EBC had MRD monitoring. 58 patients (12.5%) had +ctDNA in the adjuvant setting. Of the 58 patients, 45 (77.6%) had restaging imaging performed within 1 year of +ctDNA result and 25/45 (55.6%) were found to have radiographic evidence of recurrence at that time. Of 20 remaining patients with +ctDNA despite no radiographic evidence of recurrence, 25.0% underwent increased imaging surveillance, 70.0% had repeat ctDNA testing, and 45.0% underwent change in therapy due to +ctDNA result. Of the patients who changed therapy, 55.6% had subsequent ctDNA clearance, 80% of whom remain without radiological recurrence.

Conclusions: Adjuvant ctDNA detection impacted the care of most patients with EBC including motivating imaging and changes in therapy. Further validation of these findings is needed to inform incorporation of ctDNA testing into routine adjuvant care of EBC.