Abstract B014: Prospective analysis of circulating tumor cell dynamics during preoperative radiotherapy in locally advanced breast cancer

• Published in: Clinical cancer research 2024-11, Vol.30 (21_Supplement), p.B014-B014
• Main Authors: Goodman, Chelain R, Shaitelman, Simona F, Ramezani, Saleh, Strauss, Jonathan B., Zia, Anam, Comeaux, Nathan, Virk, Ritupreet, Lin, Ruitao, Nead, Kevin, Mitchell, Melissa P, Hoffman, Karen E, Strom, Eric, Stauder, Michael, Perkins, George, Reed, Valerie, Bloom, Elizabeth, Joyner, Melissa, Schlembach, Pamela, Valero, Vicente, Lim, Bora, Barcenas, Carlos H, Lucci, Anthony, Woodward, Wendy A, Smith, Benjamin D
• Format: Article
• Language: English
• ISSN: 1557-3265; 1557-3265
• DOI: 10.1158/1557-3265.LIQBIOP24-B014

Introduction: This is a per-protocol interim analysis of circulating tumor cell (CTC) dynamics among patients diagnosed with locally advanced breast cancer receiving preoperative radiotherapy (RT) on the TOPAz trial (“Trial of Preoperative Radiation”) with concurrent enrollment on a prospective observational cohort study (2022-0601). Methods: Eligible patients with clinical or pathologic T3-4 or node-positive non-metastatic breast cancer were prospectively enrolled. All patients received preoperative RT followed by mastectomy and were randomized to conventional fractionation (CFx, 50Gy/25Fx) versus hypofractionation (HFx, 40Gy/15Fx). CTCs were enumerated using the CellSearch® assay immediately prior to RT (Pre-RT) and within 1 week of completing RT (End of RT). Rates of CTC detection and clearance with RT were calculated. Results: As of August 2024, 46 enrolled patients had a Pre-RT assessment for CTCs, of which 45 (98%) received neoadjuvant chemotherapy (NAC), 30 (65%) had clinical T3-4 disease, 10 (22%) had advanced nodal (cN3) disease, 39 (85%) had estrogen receptor (ER)- positive disease, 3 (7%) overexpressed Her2, and 6 (13%) had triple negative disease. Prior to RT, 15 (33%) patients had ≥1 detectable CTC (median [IQR] = 2 cells [1-2.5]). Of the 14 CTC- positive patients with a completed “End of RT” blood draw to date, 11 (79%) achieved CTC clearance, while 3 patients had persistent CTCs (median [IQR] = 2 cells [1.5-2.5]). Patients who achieved CTC clearance had significantly lower median initial CTC count compared to patients who had persistent CTCs ((2 [1-2]) versus 8 [5-19], Kruskal-Wallis test, p