Can Radiologic Tumor Size Following Neoadjuvant Therapy Reliably Guide Tissue Resection in Breast Conserving Surgery in Patients with Invasive Breast Cancer?

Abstract

Optimum tissue resection volume for patients with invasive breast cancer undergoing breast conserving surgery following neoadjuvant therapy (NAT) is not known. We compared positive margin and in-breast tumor recurrence (IBTR) between 2 groups that were created based on radiologic tumor size (RTS (cm3)) at diagnosis, RTS post-NAT, and volume of tissue resected (VTL): Pre-NAT group, patients with VTL closer to RTS at diagnosis, and post-NAT group, patients with VTL closer to post-NAT RTS. 82 patients with 84 breast cancers treated with NAT between 2007 and 2017 who had pre- and post-NAT imaging were identified from a prospectively maintained database. RTS at diagnosis, RTS post-NAT, and VTL were determined. Clinical and treatment characteristics, IBTR, and disease-free survival (DFS) were compared between pre-NAT (n = 51) and post-NAT (n = 33) groups. Compared to post-NAT patients, pre-NAT patients had smaller RTS at presentation (9.2 vs. 33.5cm3, P < .001) and post-NAT (1.2 vs. 8.2cm3, P = .024). At median follow-up of 4 years, there were no differences between groups in pathologic tumor size, positive margin rate, adjuvant therapy, IBTR, or DFS. Resection volumes that matched RTS on post-NAT imaging were not associated with increased positive margins or IBTR. It may be appropriate to use post-NAT imaging to guide lumpectomy volume.