Real-time, intraoperative detection of residual breast cancer in lumpectomy cavity walls using a novel cathepsin-activated fluorescent imaging system

Obtaining tumor-free surgical margins is critical to prevent recurrence in breast-conserving surgery but it remains challenging. We assessed the LUM Imaging System for real-time, intraoperative detection of residual tumor.Lumpectomy cavity walls and excised specimens of breast cancer lumpectomy patients were assessed with the LUM Imaging System (Lumicell, Inc., Wellesley MA) with and without intravenous LUM015, a cathepsin-activatable fluorescent agent. Fluorescence at potential sites of residual tumor was evaluated with a sterile hand-held probe, displayed on a monitor and correlated with histopathology.Background autofluorescence was assessed in excised specimens from 9 patients who did not receive LUM015. In vivo lumpectomy cavities and excised specimens were then imaged in 15 women undergoing breast cancer surgery who received no LUM015, 0.5, or 1 mg/kg LUM015 (5 women per dose). Among these, 11 patients had invasive carcinoma with ductal carcinoma in situ (DCIS) and 4 had only DCIS. Image acquisition took 1 s for each 2.6-cm-diameter surface. No significant background normal breast fluorescence was identified. Elevated fluorescent signal was seen from invasive cancers and DCIS. Mean tumor-to-normal signal ratios were 4.70 ± 1.23 at 0.5 mg/kg and 4.22 ± 0.9 at 1.0 mg/kg (p = 0.54). Tumor was distinguished from normal tissue in pre-and postmenopausal women and readings were not affected by breast density. Some benign tissues produced fluorescent signal with LUM015.The LUM Imaging System allows rapid identification of residual tumor in the lumpectomy cavity of breast cancer patients and may reduce rates of positive margins.