Threshold Analysis and Biodistribution of Fluorescently Labeled Bevacizumab in Human Breast Cancer

Abstract

In vivo tumor labeling with fluorescent agents may assist endoscopic and surgical guidance for cancer therapy as well as create opportunities to directly observe cancer biology in patients. However, malignant and nonmalignant tissues are usually distinguished on fluorescence images by applying empirically determined fluorescence intensity thresholds. Here, we report the development of fSTREAM, a set of analytic methods designed to streamline the analysis of surgically excised breast tissues by collecting and statistically processing hybrid multiscale fluorescence, color, and histology readouts toward precision fluorescence imaging. fSTREAM addresses core questions of how to relate fluorescence intensity to tumor tissue and how to quantitatively assign a normalized threshold that sufficiently differentiates tumor tissue from healthy tissue. Using fSTREAM we assessed human breast tumors stained in vivo with fluorescent bevacizumab at microdose levels. Showing that detection of such levels is achievable, we validated fSTREAM for high-resolution mapping of the spatial pattern of labeled antibody and its relation to the underlying cancer pathophysiology and tumor border on a per patient basis. We demonstrated a 98% sensitivity and 79% specificity when using labeled bevacizumab to outline the tumor mass. Overall, our results illustrate a quantitative approach to relate fluorescence signals to malignant tissues and improve the theranostic application of fluorescence molecular imaging. Cancer Res; 77(3); 623-31. ©2016 AACR.

A Phase I Clinical Trial of Targeted Intraoperative Molecular Imaging for Pulmonary Adenocarcinomas

“…The low toxicity profile of OTL38 echoes safety observed with other IMI agents being evaluated in phase [12], bevacizumab-IRDye800 [22], and cetuximab-IRDye800 [7] have displayed almost exclusively grade I/II toxicities. This provides important patient safety advantages over other localization techniques such as percutaneous wire placement, lymph node mapping, and fluoroscopy [23].…”

Roadmap for the Development and Clinical Translation of Optical Tracers Cetuximab-800CW and Trastuzumab-800CW

“…Because of developmental challenges and lack of established guidelines for development or implementation, the number of tracers reaching the clinical trial phase has remained limited. Among tracers based on IRDyeconjugated antibodies, only bevacizumab (20,28,29), girentuximab (30), cetuximab (19), and panitumumab (31,32) have running or completed clinical trials.…”

Signal to Noise Ratio as a Cross-Platform Metric for Intraoperative Fluorescence Imaging

“…This background variation can occur over a wide frequency scale. Notably, variations in antibody distribution and binding cannot be predicted a priori , prohibiting the use of a global threshold for MRD and current efforts at background subtraction are limited to centimeter-scale tumor foci 9 . For example, the standard deviation for antibody binding per square micron in tissue labeled with an antibody in vivo ( Figure 2) ranged from 1,259 antibodies/μm 2 in a HER2-negative tumor (e.g.…”

“…The default method for identifying residual tumor using intraoperative imagers has been physician identification from an image. Efforts to define a common quantification metric for imaging tools have centered around the signal-to-background ratio (SBR) 8,9 . Implicit in this metric is a tumor signal significantly above background -true for larger tumor foci, but not necessarily for microscopic disease, which is often just above background contributed by non-specific binding, autofluorescence, and other optical and electronic sources.…”