The Effect of Wire Versus Magnetic Seed Localization on Lumpectomy Cavity Size

Michael Dykstra; Jessica Thompson; Jessica Aldous; Shannon Jiang; Tasha Hughes; James Hayman; Aleksandar Dragovic; Jennifer Shah; Alfred Chang; Corey Speers; Michael Sabel; Lesly Dossett; Matthew Schipper; Reshma Jagsi

doi:10.1016/j.prro.2023.12.004

The Effect of Wire Versus Magnetic Seed Localization on Lumpectomy Cavity Size

Pract Radiat Oncol. 2023 Dec 30:S1879-8500(23)00347-8. doi: 10.1016/j.prro.2023.12.004. Online ahead of print.

Authors

Affiliations

¹ Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan.
² Department of Surgery, Division of Surgical Oncology, Corewell Health Medical Group, Grand Rapids, Michigan.
³ Department of Radiation Oncology, Washington University School of Medicine, St Louis, Missouri.
⁴ Department of Surgery, Division of Surgical Oncology, University of Michigan, Ann Arbor, Michigan.
⁵ Department of Radiation Oncology, Case Western Reserve University, Cleveland, Ohio.
⁶ Department of Radiation Oncology, University of Michigan, Ann Arbor, Michigan; Department of Radiation Oncology, Winship Cancer Institute of Emory University, Atlanta, Georgia. Electronic address: rjagsi@emory.edu.

PMID: 38161002
DOI: 10.1016/j.prro.2023.12.004

Abstract

Purpose: Our purpose was to assess whether an association exists between surgical localization technique and lumpectomy cavity size on radiation therapy planning computed tomography (CT) scan.

Methods and materials: A single-institution retrospective review was conducted of women undergoing breast conserving surgery with wire or magnetic seed guided lumpectomy followed by adjuvant radiation therapy from 2018 to 2021. Patients of a surgeon only performing 1 localization technique or undergoing bracketed localization were excluded. The primary outcome was lumpectomy cavity size on simulation CT. Confounding due to imbalance in patient and tumor factors was addressed with overlap weights derived from a propensity score analysis and used in a weighted multivariable analysis. Secondary outcomes included positive margins, total pathologic volume, boost delivery, and boost modality.

Results: Of 617 women who received lumpectomy during the study period, 387 were included in final analysis. Tumors of patients undergoing seed localization were more likely unifocal, assessable by ultrasound, and smaller. Seed use rates ranged from 27.7% to 70.7% per surgeon. There was no difference in positive margins (6.4 vs 5.4%, P = .79) or second surgeries (9.4 vs 8.1%, P = .79) between groups. Close margin rates were similar for ductal carcinoma in situ (P = .35) and invasive carcinoma (P = .97). In unadjusted bivariable analyses, wire localization was associated with larger total pathology volume (P = .004), but localization technique showed no association with CT cavity volume (P = .15). After adjusting for potentially confounding variables, multivariable analysis failed to show an association between localization technique and either CT cavity (P = .35) or total path volume (P = .08). There was no difference in indicated-boost delivery (P = .15) or electron boost (P = .14) by localization technique.

Conclusions: There was no significant difference in CT cavity size by localization technique, suggesting choice between surgical techniques does not impede radiation therapy boost delivery.