Purpose The inability to visualize cancer during prostatectomy contributes to positive margins, cancer recurrence, and surgical side effects. A molecularly targeted fluorescent probe offers the potential for real-time intra-operative imaging. The goal of this study was to develop a probe for image-guided prostate cancer surgery. Experimental Design An antibody fragment (cys-diabody, cDb) against prostate stem cell antigen (PSCA) was conjugated to a far-red fluorophore, Cy5. The integrity and binding of the probe to PSCA was confirmed by gel electrophoresis, size exclusion and flow cytometry, respectively. Subcutaneous models of PSCA-expressing xenografts were used to assess the biodistribution and in vivo kinetics, while an invasive intramuscular model was utilized to explore the performance of Cy5-cDb-mediated fluorescence guidance in representative surgical scenarios. Finally, a prospective, randomized study comparing surgical resection with and without fluorescent guidance was performed to determine if this probe could reduce the incidence of positive margins. Results Cy5-cDb demonstrated excellent purity, stability and specific binding to PSCA. In vivo imaging showed maximal signal-to-background ratios at 6 hours. In mice carrying PSCA+ and − dual xenografts, the mean fluorescence ratio of PSCA+/− tumors was 4.4:1. In surgical resection experiments, residual tumors <1mm that were missed on white light surgery were identified and resected using fluorescence guidance, which reduced the incidence of positive surgical margins (0/8) compared to white light surgery alone (7/7). Conclusions Fluorescently labeled cDb enables real-time in vivo imaging of prostate cancer xenografts in mice, and facilitates more complete tumor removal than conventional white light surgery alone.
Purpose of Review Novel tools have become available to the practicing urologist in recent years that endeavor to improve on commonly utilized prostate cancer (PCa) risk stratification techniques. In this review, we provide an overview of these modalities in the context of active surveillance. Recent Findings Multiparametric magnetic resonance imaging (MP-MRI) has a rapidly growing body of evidence that suggests it provides the necessary sensitivity and NPV to rule out clinically significant disease. MRI-guided targeted biopsy has the potential to improve detection of clinically significant cancers and for rebiopsy of patients with continued suspicion for PCa. PSA isoforms and Prostate Health Index (PHI) outperform PSA alone and improve risk stratification when combined with established criteria, but need further prospective studies using template and MRI-targeted biopsies. Urinary biomarkers tend to fall short in predicting adverse pathology when used alone, but improve risk-stratification when used in conjunction and with established criteria. Finally, tissue biomarkers and gene assays allow for patient-specific molecular and genetic characterization of cancer phenotype, showing significant promise in predicting adverse pathology and in some cases have already been incorporated into and altered clinical practice. Summary These novel modalities show remarkable promise in improving the risk-stratification of patients with PCa, and as the body of evidence grows will likely become incorporated into major oncologic guidelines and standard urologic practice. Further prospective clinical studies are needed, as well as analysis of cost-effectiveness.
<p>Figure S1. Biochemical characterization of Cy5 conjugated anti-PSCA cys-Diabody. Figure S2. Validation of in vivo tumor detection using endogenously PSCA-expressing line LAPC-9 Figure S3. Determining the optimal time point for in vivo Cy5-cDb imaging. Figure S4. Cy5-cDb enabled fluorescence-guided surgical resection of PSCA-expressing tumors. Figure S5. LAPC-9 intramuscular tumor extent was not readily detectable under white light (A-B), but was clearly visible under fluorescence guidance (C). Figure S6. Intraoperative white light and florescent images of 22Rv1 intramuscular xenografts utilizing anti-PSCA Cy5-cDb. Figure S7. Additional H&E histopathology of tumor margins from the prospective, randomized trial.</p>
<div>Abstract<p><b>Purpose:</b> The inability to visualize cancer during prostatectomy contributes to positive margins, cancer recurrence, and surgical side effects. A molecularly targeted fluorescent probe offers the potential for real-time intraoperative imaging. The goal of this study was to develop a probe for image-guided prostate cancer surgery.</p><p><b>Experimental Design:</b> An antibody fragment (cys-diabody, cDb) against prostate stem cell antigen (PSCA) was conjugated to a far-red fluorophore, Cy5. The integrity and binding of the probe to PSCA was confirmed by gel electrophoresis, size exclusion, and flow cytometry, respectively. Subcutaneous models of PSCA-expressing xenografts were used to assess the biodistribution and <i>in vivo</i> kinetics, whereas an invasive intramuscular model was utilized to explore the performance of Cy5-cDb–mediated fluorescence guidance in representative surgical scenarios. Finally, a prospective, randomized study comparing surgical resection with and without fluorescent guidance was performed to determine whether this probe could reduce the incidence of positive margins.</p><p><b>Results:</b> Cy5-cDb demonstrated excellent purity, stability, and specific binding to PSCA. <i>In vivo</i> imaging showed maximal signal-to-background ratios at 6 hours. In mice carrying PSCA<sup>+</sup> and negative (−) dual xenografts, the mean fluorescence ratio of PSCA<sup>+/−</sup> tumors was 4.4:1. In surgical resection experiments, residual tumors <1 mm that were missed on white light surgery were identified and resected using fluorescence guidance, which reduced the incidence of positive surgical margins (0/8) compared with white light surgery alone (7/7).</p><p><b>Conclusions:</b> Fluorescently labeled cDb enables real-time <i>in vivo</i> imaging of prostate cancer xenografts in mice, and facilitates more complete tumor removal than conventional white light surgery alone. <i>Clin Cancer Res; 22(6); 1403–12. ©2015 AACR</i>.</p><p><i>See related commentary by van Leeuwen and van der Poel, p. 1304</i></p></div>
<div>Abstract<p><b>Purpose:</b> The inability to visualize cancer during prostatectomy contributes to positive margins, cancer recurrence, and surgical side effects. A molecularly targeted fluorescent probe offers the potential for real-time intraoperative imaging. The goal of this study was to develop a probe for image-guided prostate cancer surgery.</p><p><b>Experimental Design:</b> An antibody fragment (cys-diabody, cDb) against prostate stem cell antigen (PSCA) was conjugated to a far-red fluorophore, Cy5. The integrity and binding of the probe to PSCA was confirmed by gel electrophoresis, size exclusion, and flow cytometry, respectively. Subcutaneous models of PSCA-expressing xenografts were used to assess the biodistribution and <i>in vivo</i> kinetics, whereas an invasive intramuscular model was utilized to explore the performance of Cy5-cDb–mediated fluorescence guidance in representative surgical scenarios. Finally, a prospective, randomized study comparing surgical resection with and without fluorescent guidance was performed to determine whether this probe could reduce the incidence of positive margins.</p><p><b>Results:</b> Cy5-cDb demonstrated excellent purity, stability, and specific binding to PSCA. <i>In vivo</i> imaging showed maximal signal-to-background ratios at 6 hours. In mice carrying PSCA<sup>+</sup> and negative (−) dual xenografts, the mean fluorescence ratio of PSCA<sup>+/−</sup> tumors was 4.4:1. In surgical resection experiments, residual tumors <1 mm that were missed on white light surgery were identified and resected using fluorescence guidance, which reduced the incidence of positive surgical margins (0/8) compared with white light surgery alone (7/7).</p><p><b>Conclusions:</b> Fluorescently labeled cDb enables real-time <i>in vivo</i> imaging of prostate cancer xenografts in mice, and facilitates more complete tumor removal than conventional white light surgery alone. <i>Clin Cancer Res; 22(6); 1403–12. ©2015 AACR</i>.</p><p><i>See related commentary by van Leeuwen and van der Poel, p. 1304</i></p></div>
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