Abstract P3-13-10: A comparison of the micro-impulse radar SAVI SCOUT to the radioactive I125 seed in localization of non-palpable breast cancer for breast conserving therapy
Authors: Nolano SE , Thalhiemer LO , Yu E , Grujic E , Carter WB , Frazier TG 
Published: March 2017

Breast conservation and primary radiation (BCT) is a widely used treatment for early stage breast cancer patients. Studies report a 20-40 percent re-excision rate to obtain clear margins. Current localization practices include needle, radioactive seed and intraoperative U/S. Seed localization has been found to decrease tissue volume excision and improve patient satisfaction. However, radioactive seed programs are difficult to implement due to cumbersome regulations by the Nuclear Regulatory Commission (NRC). SAVI SCOUT® is a new technology cleared by the FDA for tumor localization. This device utilizes non-radioactive, micro-impulse radar (radar) to provide surgical guidance. The aim of this study was to evaluate the SCOUT® and determine its equivalence to seed localization by comparing re-excision rates and specimen volume.

70 patients with clinical stage 0, I, or II breast cancer who were treated with BCT were included in this IRB approved review. 35 patients were compared using the SCOUT radar localization technique with 35 patients using the radioactive iodine 125 seed localization technique. All patients received a wide segmental resection. The tissue was oriented and assessed clinically (visualization and palpation) and radiographically (Kubtec's XPERT 40 Digital Specimen Radiography System) in the operating room. Additional margins were excised if deemed to be suspicious by the surgeon (unless the anterior margin was skin or the posterior margin was the pectoral muscle fascia). Final margin status for both groups was compared. A positive margin was any margin with tumor on ink. The total volume of the excised specimen plus additional margins was recorded by the pathologist.

In all 70 patients, the targeted lesions, seed and/or reflectors were successfully removed. There were 420 margins assessed (6 for each specimen), using the additional margins excised as the final margin for evaluation of tumor on ink. Of the 210 final margins in the specimens excised using the seed, 5 margins (2.38%) in 4 patients were positive. 5 margins (2.38%) were also positive in 4 patients using the SCOUT. Nine patients in total returned to the operating room for re-excision. [One re-excision was performed as physician preference for close (&lt;2mm) margins for DCIS.] 5/9 patients requiring re-excision were found to have residual disease. A total of 119 additional margins were excised from 51 patients at the initial operation. 68 margins from 26 patients (SCOUT) and 51 margins from 25 patients (seed). Of the 119, 5 margins were found to be positive. 3 margins 4.41% (3/68) in the SCOUT group and 2 margins 3.92% (2/51) in the seed group. The average volume resected from the SCOUT averaged 81.28 cm3 while the volume of the seed averaged 100.39 cm3 (p-value 0.209).

The use of SCOUT for non-palpable tumor localization was equivalent to seed localization when comparing margin re-excision rate and tissue volumes. We conclude that SCOUT is an excellent alternative in breast cancer localization and can be easily implemented in most hospitals for breast conservation therapy.

Citation Format: Nolano SE, Thalhiemer LO, Yu E, Grujic E, Carter WB, Frazier TG. A comparison of the micro-impulse radar SAVI SCOUT to the radioactive I125 seed in localization of non-palpable breast cancer for breast conserving therapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P3-13-10.