Background: Ductal carcinoma in situ (DCIS) is a non-invasive form of early breast cancer, with a poorly
understood natural history of invasive transformation. Necrosis is a well-recognized adverse prognostic feature of
DCIS, and non-invasive detection of its presence and spatial extent could provide information not obtainable by
biopsy. We describe here imaging of the distribution and extent of comedo-type necrosis in a model of human
DCIS using C2Am, an imaging agent that binds to the phosphatidylserine exposed by necrotic cells.
Methods: We used an established xenograft model of human DCIS that mimics the histopathological features of
the disease. Planar near-infrared and optoacoustic imaging, using fluorescently labeled C2Am, were used to image
non-invasively the presence and extent of lesion necrosis.
Results: C2Am showed specific and sensitive binding to necrotic areas in DCIS tissue, detectable both in vivo and
ex vivo. The imaging signal generated in vivo using near-infrared (NIR) fluorescence imaging was up to 6-fold
higher in DCIS lesions than in surrounding fat pad or skin tissue. There was a correlation between the C2Am NIR
fluorescence (Pearson R = 0.783, P = 0.0125) and optoacoustic signals (R > 0.875, P < 0.022) in the DCIS lesions in vivo and the corresponding levels of cell death detected histologically. Conclusions: C2Am is a targeted multi-modal imaging agent that could complement current anatomical imaging methods for detecting DCIS. Imaging the presence and spatial extent of necrosis may give better prognostic information than that obtained by biopsy alone.

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