Abstract PS2-10-03: Impact of Circulating Tumor DNA (ctDNA) monitoring on Patient Anxiety and Clinician Decision-Making in Early-Stage Breast Cancer (PACE-ctDNA)

Abstract Background: Prior studies show ctDNA is a promising biomarker for detecting minimal residual disease (RD), but impact on patient (pt)-reported outcomes and physician decision-making is unknown. With growing adoption of ctDNA assays such as the Signatera™ RD Test, understanding the effect of ctDNA monitoring on pt anxiety and physician treatment choices is increasingly important. We previously reported 6 month (mo) interim results and here present updated findings at 12mo. Methods: Women ≥18y.o. with triple negative (TNBC) RD or hormone receptor positive (HR+) BC were enrolled during adjuvant surveillance. CtDNA testing was q6mo and continued for 12mo or until recurrence. Pt-Reported Outcomes Measurement Information System (PROMIS) and Provider Decision Assessment Tool (PDAT) scores were collected q6mos. Both used 5-point Likert scales: higher PROMIS scores reflect greater anxiety; higher PDAT scores reflect greater physician confidence. Mean scores were compared baseline vs 6mo and vs 12mo. Results: 67 pts enrolled (mean age: 56 y; range: 24-84). Of 45 (67.2%) pts with TNBC, stage I, II, III distribution was 26.7%, 53.3%, 20.0%, respectively. Of 22 (32.8%) pts with HR+ BC, stage I, II, III was 13.6%, 68.2%, 18.2%, respectively. 64 pts completed ctDNA testing; 7/64 (10.9%) were ctDNA+ at baseline. Of these, 3/7 (42.8%) had imaging-confirmed recurrence; 1/7 (14.3%) had negative baseline imaging and progression at 6 mos; 3/7 (42.9%) had negative imaging at baseline with ctDNA clearance on adjuvant therapy at 6mos. 4 pts who were initially ctDNA- became ctDNA+ on subsequent testing. 3/4pts had recurrence on scans at the time of ctDNA+; 1/4pts had ctDNA clearance at 12mos. Recurrent pts came off study and did not continue PROMIS testing. 23 ctDNA- pts completed ctDNA testing and PROMIS surveys at baseline, 6 and 12mos. There was no statistically significant change in scores over time and a trend toward decreasing anxiety scores in ctDNA- pts. 4 ctDNA+ pts remained on study and had PROMIS scores before and after ctDNA result (table 1). 5 physicians managing ctDNA+ pts completed a PDAT after ctDNA results. Overall decision-making scores were similar after ctDNA+ or ctDNA- results (37.8 vs. 37.1, p = 0.76); physicians caring for ctDNA+ pts self-reported lower confidence in treatment decisions (3.6 vs. 4.3). All ctDNA+ pts had imaging. Conclusion: Pt-reported anxiety was stable over time in ctDNA- pts with a trend toward lower anxiety scores. PROMIS scores after ctDNA+ result were available for only 4 pts who remained on study; as pts with recurrence came off study, we cannot fully assess how ctDNA+ results affect anxiety but present raw data. CtDNA+ results were associated with lower self-report of confidence in treatment decisions among 5 responding physicians, suggesting that without clear clinical guidelines, ctDNA surveillance can introduce uncertainty for providers. Citation Format: D. Isseroff, N. Wiesendanger, A. Kahn, D. O'Neil, M. Cohenuram, A. Bulgaru, K. Fenn, J. LaSala, S. Kert, N. Fischbach, J. Kanowitz, R. Legare, M. DiGiovanna, A. Silber, T. Sanft, S. Schellhorn, H. Sethi, E. Kalashnikova, S. Rivero-Hinojosa, M. Liu, I. Krop, E. Winer, W. Wei, M. Lustberg, L. Pusztai, M. Rozenblit. Impact of Circulating Tumor DNA (ctDNA) monitoring on Patient Anxiety and Clinician Decision-Making in Early-Stage Breast Cancer (PACE-ctDNA) [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS2-10-03.