A Patient-Specific 3D-Printed Form Accurately Transfers Supine MRI-Derived Tumor Localization Information to Guide Breast-Conserving Surgery

Background. Wire-localized excision of nonpalpable breast cancer is imprecise, resulting in positive margins 25-30% of the time. Methods. Patients underwent preoperative supine magnetic resonance imaging (MRI). A radiologist outlined the tumor edges on consecutive images, creating a three-dimensional (3D) view of its location. Using 3D printing, a bra-like plastic form (the Breast Cancer Locator [BCL]) was fabricated, with features that allowed a surgeon to (1) mark the edges of the tumor on the breast surface; (2) inject blue dye into the breast 1 cm from the tumor edges; and (3) place a wire in the tumor at the time of surgery. Results. Nineteen patients with palpable cancers underwent partial mastectomy after placement of surgical cues using patient-specific BCLs. The cues were in place in < 5 min and no adverse events occurred. The BCL accurately localized 18/19 cancers. In the 18 accurately localized cases, all 68 blue-dye injections were outside of the tumor edges. Median distance from the blue-dye center to the pathologic tumor edge was 1.4 cm, while distance from the blue dye to the tumor edge was < 5 mm in 4% of injections, 0.5-2.0 cm in 72% of injections, and > 2 cm in 24% of injections. Median distance from the tumor center to the BCL-localized wire and to the clip placed at the time of diagnosis was similar (0.49 vs. 0.73 cm) on specimen mammograms. Conclusions. Information on breast cancer location and shape derived from a supine MRI can be transferred safely and accurately to patients in the operating room using a 3D-printed form.