Near-Infrared Fluorescent Sentinel Lymph Node Mapping for Breast Cancer

The standard of care in breast cancer surgery includes identification and assessment of the sentinel lymph node (SLN). At the present time, SLN mapping utilizes a gamma ray-emitting radiotracer and/or a blue dye. Radiotracers provide sensitive detection of SLNs, but require involvement of a nuclear medicine physician, vary widely in transit time depending on the agent employed, can be difficult to localize with a handheld gamma probe, and expose both patient and caregivers to ionizing radiation. Blue dyes, such as isosulfan blue, cannot be seen easily through skin and fat, but can aid in definitive identification of the SLN when the handheld gamma probe gives ambiguous results. Finally, the learning curve associated with expertise in the SLN procedure is quite long using currently available techniques.

In this 12-patient pilot study, we are testing a new intraoperative imaging system that we developed for image-guided surgery. The imaging system uses invisible, near-infrared (NIR) light to visualize lymphatic flow and to identify the SLN. The imaging system makes no contact with the patient and can display surgical anatomy simultaneously with NIR fluorescence.

All patients will receive the standard of care for SLN mapping, namely technetium-99m sulfur colloid lymphoscintigraphy. In addition, patients will be injected with indocyanine green (ICG) diluted in human serum albumin (HSA). ICG is already FDA approved for other indications and is used in this study at 400-fold to 2000-fold lower than the typical clinical dose. Dilution into HSA improves the brightness of ICG by over 3-fold, making it an excellent tracer for lymphatic flow.

The purpose of this pilot study is to determine whether the ergonomics of the imaging system interfere with typical clinical workflow during breast cancer surgery. A secondary goal is to optimize the imaging parameters (light levels, exposure time, etc.) associated with identification of the SLN.