Abstract PS06-06: Analysis of ctDNA for the detection of minimal residual disease (MRD) using a tissue-free, multiomic assay in patients with early-stage breast cancer

Abstract Background: The detection of ctDNA in patients with early-stage breast cancer after completion of adjuvant therapy is associated with a high risk of recurrence. Current clinical guidelines do not recommend routine screening for metastatic disease unless there are clinical signs and symptoms in patients who completed adjuvant therapy. However, ctDNA may serve as an early biomarker of recurrence which may allow effective identification of patients with asymptomatic distant metastases or molecular relapse only, who could benefit from early treatment intervention. Herein, we utilized a tissue-free, multiomic assay for the sensitive and specific detection of MRD in patients with early-stage breast cancer. Methods: Plasma samples were collected from patients with stage I-III breast cancer who were enrolled in the SUCCESS-A phase 3 clinical trial (NCT02181101) between 2006 and 2007. All patients received adjuvant chemotherapy +/- endocrine therapy and/or anti-HER2 therapy. Samples were collected approximately two years after completion of adjuvant chemotherapy, and plasma samples selected for analysis were from patients without evidence of disease recurrence prior to sample collection. Presence of MRD was assessed using Guardant Reveal powered by Infinity, which evaluates the epigenomic signals associated with cancer versus normal DNA for the detection of ctDNA. Samples with the presence of ctDNA are characterized for somatic alterations with common sources of interference such as clonal hematopoiesis excluded. An analytically validated bioinformatics pipeline was used for the detection of breast cancer ctDNA. Samples were analyzed blinded to the clinical data. Median survival times were estimated using the Kaplan-Meier method and hazard ratios were calculated based on univariable cox regression models. Results: A total of 311 plasma samples from 311 patients were evaluable. ctDNA was detected in 34% (13/38) of patients who subsequently developed distant recurrence and in none (0/7) of the patients who had local or contralateral breast cancer recurrence. ctDNA was detected in 60% (9/15) of samples that were collected within one year before recurrence. In the ctDNA detected samples from patients who had disease recurrence, the median time from sample collection to recurrence was 7.9 months (range, 1.4-28.6 months). ctDNA was detected in 6 patients who did not have a documented disease recurrence, resulting in a specificity of 97.7% (260/266). In the overall cohort, ctDNA detection was prognostic for recurrence-free survival (RFS; HR 11.0, 95% CI 2.28-53.6; p 0.0001), distant recurrence-free survival (D-RFS; HR 13.7, 95% CI 2.52-74.9; p 0.0001), and overall survival (OS; HR 17.4, 95% CI 1.33-227; p 0.0001). Conclusion: Detection of ctDNA after adjuvant chemotherapy was highly prognostic and demonstrated high specificity in an early-stage breast cancer cohort. Larger, prospective studies are needed to confirm the prognostic value of ctDNA in the post-treatment setting and assess the clinical utility of MRD detection in this population. Citation Format: Wolfgang Janni, Thomas Friedl, Brigitte Rack, Peter A. Fasching, Andreas Hartkopf, Hans Tesch, Ralf Lorenz, Georg Heinrich, Jens-Uwe Blohmer, Tanja Fehm, Volkmar Müller, Andreas Schneeweiss, Matthias Beckmann, Matthias Ruebner, Nadia Harbeck, Klaus Pantel, Derek Dustin, Mingyang Cai. Analysis of ctDNA for the detection of minimal residual disease (MRD) using a tissue-free, multiomic assay in patients with early-stage breast cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PS06-06.