Radiofrequency ablation of breast cancer lumpectomy cavities – a technique intended to increase negative margins after breast conservation surgery. From benchtop to clinical use.

Abstract #4136 INTRODUCTION: Following breast conservation surgery, up to 49% of women require additional surgery due to close or positive lumpectomy margins. This results in significant additional burden for patient and society. This in vivo study assesses the feasibility of using intraoperative radiofrequency ablation (RFA) to treat the lumpectomy cavity walls and in situ extend the final negative margins, with consequent reduced need for re-excision surgery.
 METHODS: First, an in vitro study was performed to establish the performance characteristics of a RFA device in 12 mock lumpectomy cavities in fresh human breast or panniculus. These cavities were RFA-treated for 18 minutes with thermocouples recording. Second, an in vivo feasibility study was performed in 10 breast cancer pts (Italy) with clinically less than 2 cm tumors. The patients underwent lumpectomy, followed by in vivo 15 minute RFA cavity treatment, and subsequent quadrantectomy of the treated region. Third, an initial 5 pts (Spain) underwent lumpectomy and RFA only, with 4-5 punch biopsies obtained from the radial resection margin. The devitalized tissue radii around the cavity were measured using triphenyltetrazolium chloride (TTC) viability staining.
 RESULTS: In vitro temperatures in excess of 55C for 5 minutes were obtained 3mm from the radiofrequency probe and exceeded 45C at the treatment region edge. The in vitro and in vivo anterior/posterior treatment zone heights were 3.9 ± 0.5 cm and 4.4 ± 1.3 cm, respectively. The in vitro and in vivo distance between the anterior ablation zone edge and adjacent skin dermis measured 1.4 ± 1.1 cm and 0.9 ± 0.6 cm, respectively. The ablation zone edge focally extended to the dermal junction in one in vivo case. The three-dimensional devitalized tissue radii are presented in Table 1. In the 5 patients (Spain) where respective ablation radii were verified by punch biopsies, the devitalized tissue typically extended beyond the 7-14 mm radial depth of the biopsy sample. There were no postoperative complications with the use of RFA.
 CONCLUSIONS: This pilot data supports the feasibility of adjuvant radiofrequency lumpectomy cavity treatment to extend final negative tissue margins by approximately 1 cm. The extended margins have the potential to reduce the number of patients requiring re-excision surgery for close or focally positive margins. A multi-center trial aimed at validation of this technique has recently started. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4136.