Traditionally, the evaluation of tumor margins is done by pathologists who examine the tumor after it has been surgically removed. However, this method often faces challenges as the removed tumor samples can become distorted, complicating the assessment of margin orientation, and the results can also take several days. Now, a promising new technique can enable surgeons to identify and remove any remaining tumor tissue during breast-conserving surgery and has shown encouraging results in a clinical trial.

In the multi-center study, researchers from the Mass General Cancer Center (Boston, MA, USA) examined Lumicell, Inc.’s (Newton, MA, USA) investigational optical imaging agent pegulicianine in fluorescence-guided surgery (pFGS). The pFGS technique involves injecting a fluorescent dye called pegulicianine before the surgery. After removing the primary tumor, surgeons use a handheld probe to scan the lumpectomy cavity for residual tumor tissue while image analysis software displays any fluorescent signal indicating remaining tumor tissue on a screen. The research team found that pFGS helped in removing residual tumor cells left behind after standard lumpectomy procedures or eliminated the need for a second surgery in 10% of the patients in the study.

The prospective trial to assess the effectiveness of pFGS enrolled 406 patients at 14 U.S. sites, all of whom were undergoing lumpectomy for stage 1 to 3 invasive breast cancer and/or ductal in situ carcinoma (the earliest form of breast cancer). In the group that received pFGS, surgeons first performed the standard lumpectomy, then removed additional tissue based on pFGS guidance. The study demonstrated that pFGS detected remaining tumor tissue in 27 out of 357 patients (7.6%) who underwent the procedure, which had been overlooked during the standard lumpectomy. In patients with positive margins after standard surgery, pFGS successfully cleared all margins in 9 out of 62 (17%) cases, potentially avoiding the need for a second surgery. The safety profile of the pFGS approach was favorable, with a low and comparable rate of allergic reactions to other commonly used imaging agents.

The research team also evaluated the diagnostic performance of pFGS by determining the percentage of margins with tumors that were pFGS positive (sensitivity), and the percentage of margins without tumors that were pFGS negative (specificity). The sensitivity was 49.3% across all study margins and 58.6% for margins where a direct comparison with histopathology was available, while the specificity was 85.2%. Although the trial met the predetermined thresholds for removal of residual tumor and specificity, it did not achieve its set sensitivity goal, possibly due to the trial design, which excluded taking additional margin specimens in cases of negative pFGS readings. The researchers are now conducting further studies to calculate sensitivity more accurately by obtaining additional margin tissue. They will also explore how effectively pFGS clears margins, comparing outcomes with standard surgery and recurrence rates.

"Our aim with this research is to assess methods for enhancing the efficacy of lumpectomy surgery, lessening the burden on patients, and assisting surgeons in achieving clean margins," explained Barbara Smith, MD, PhD, the corresponding author and the director of the Breast Program at Mass General Cancer Center, as well as the head of the Breast Section in the Department of Surgery. "In our study, this intervention had a positive impact on 10% of the patients we examined. By assessing margins in real-time, surgeons can promptly remove any remaining tissue." 

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