Real-time intraoperative detection of breast cancer using near-infrared fluorescence imaging and Methylene Blue

Abstract

Background: Despite recent developments in preoperative breast cancer imaging, intraoperative localization of tumor tissue can be challenging, resulting in tumor-positive resection margins during breast conserving surgery. Based on certain physicochemical similarities between Technetium((99m)Tc)-sestamibi (MIBI), an SPECT radiodiagnostic with a sensitivity of 83-90% to detect breast cancer preoperatively, and the near-infrared (NIR) fluorophore Methylene Blue (MB), we hypothesized that MB might detect breast cancer intraoperatively using NIR fluorescence imaging.

Methods: Twenty-four patients with breast cancer, planned for surgical resection, were included. Patients were divided in 2 administration groups, which differed with respect to the timing of MB administration. N = 12 patients per group were administered 1.0 mg/kg MB intravenously either immediately or 3 h before surgery. The mini-FLARE imaging system was used to identify the NIR fluorescent signal during surgery and on post-resected specimens transferred to the pathology department. Results were confirmed by NIR fluorescence microscopy.

Results: 20/24 (83%) of breast tumors (carcinoma in N = 21 and ductal carcinoma in situ in N = 3) were identified in the resected specimen using NIR fluorescence imaging. Patients with non-detectable tumors were significantly older. No significant relation to receptor status or tumor grade was seen. Overall tumor-to-background ratio (TBR) was 2.4 ± 0.8. There was no significant difference between TBR and background signal between administration groups. In 2/4 patients with positive resection margins, breast cancer tissue identified in the wound bed during surgery would have changed surgical management. Histology confirmed the concordance of fluorescence signal and tumor tissue.

Conclusions: This feasibility study demonstrated an overall breast cancer identification rate using MB of 83%, with real-time intraoperative guidance having the potential to alter patient management.

Keywords: Breast cancer; Image-guided surgery; Methylene Blue; Near-infrared fluorescence imaging.

Figure 1. NIR fluorescence imaging of a tumor resection with negative margins

A. Resected specimen after wide local excision. No fluorescent signal was seen at resection margins. B. Inspection of wound bed after resection. No fluorescent signal was seen at resection margins. C. Sliced resection specimen at Pathology department. A clear fluorescent spot (arrow) was seen at the location of the tumor. Tumor was an infiltrating ductal adenocarcinoma, grade 2, ER+ PR+ Her2/neu−.

Figure 2. Tumor-to-Background Ratio and microscopic images of resected lesion

A. Overall Tumor-to-Background Ratio (TBR) and TBR per administration group are shown. No differences in TBR between administration groups were observed (P = 0.50; 95% CI −0,49 – 0,96). B. Microscopic images of Hematoxylin and Eosin staining of the resected lesion and fluorescent signal (Odyssey Infrared Imaging System, LI-COR). At the NIR fluorescent image, fluorescent signal is seen as white, where surrounding breast tissue remains black. A clear overlay between fluorescent signal and tumor tissue was seen. Normal breast tissue was indicated by an asterisk (*). Tumor (indicated by arrowhead) was an infiltrating ductal adenocarcinoma, grade 2, ER + PR + Her2/neu −.

Figure 3. NIR fluorescence imaging of a tumor resection with positive margins

A. Resected specimen after wide local excision. Fluorescent signal was seen at the deep margin of the resection specimen, indicated by arrows. B. Inspection of wound bed after resection. Fluorescent signal was seen at resection margins indicated by arrows. Direct re-resection of the fluorescent tissue was performed, which contained malignant tumor tissue. Tumor was an infiltrating lobular adenocarcinoma, grade 2, ER+ PR− Her2/neu −.