Real-time wireless tumor tracking during breast conserving surgery

Abstract

Purpose

To evaluate a novel surgical navigation system for breast conserving surgery (BCS), based on real-time tumor tracking using the Calypso \(\circledR \) 4D Localization System (Varian Medical Systems Inc., USA). Navigation-guided breast conserving surgery (Nav-BCS) was compared to conventional iodine seed-guided BCS ( \(^{125}\) I-BCS).

Methods

Two breast phantom types were produced, containing spherical and complex tumors in which wireless transponders (Nav-BCS) or a iodine seed ( \(^{125}\) I-BCS) were implanted. For navigation, orthogonal views and 3D volume renders of a CT of the phantom were shown, including a tumor segmentation and a predetermined resection margin. In the same views, a surgical pointer was tracked and visualized. \(^{125}\) I-BCS was performed according to standard protocol. Five surgical breast oncologists first performed a practice session with Nav-BCS, followed by two Nav-BCS and \(^{125}\) I-BCS sessions on spherical and complex tumors. Postoperative CT images of all resection specimens were registered to the preoperative CT. Main outcome measures were the minimum resection margin (in mm) and the excision times.

Results

The rate of incomplete tumor resections was 6.7% for Nav-BCS and 20% for \(^{125}\) I-BCS. The minimum resection margins on the spherical tumors were 3.0 ± 1.4 mm for Nav-BCS and 2.5 ± 1.6 mm for \(^{125}\) I-BCS (p = 0.63). For the complex tumors, these were 2.2 ± 1.1 mm (Nav-BCS) and 0.9 ± 2.4 mm ( \(^{125}\) I-BCS) (p = 0.32). Mean excision times on spherical and complex tumors were 9.5 ±  2.7 min and 9.4 ± 2.6 min (Nav-BCS), compared to 5.8 ± 2.2  min and 4.7 ± 3.4 min ( \(^{125}\) I-BCS, both (p < 0.05).

Conclusions

The presented surgical navigation system improved the intra-operative awareness about tumor position and orientation, with the potential to improve surgical outcomes for non-palpable breast tumors. Results are positive, and participating surgeons were enthusiastic, but extended surgical experience on real breast tissue is required.