Abstract 216: Pancreatic cancer fluorescence-­guided surgery with a fluorophore­-conjugated antibody to carcinoembryonic antigen (CEA) improves surgical resection and increases disease-free and overall survival in orthotopic mouse models

We established nude­ mouse models of human pancreatic cancer with surgical orthotopic implantation of the human BxPC­3 pancreatic cancer for fluorescence-guided surgery (FGS). After 2 weeks, mice then underwent bright-­light surgery (BLS) or FGS 24 hours after intravenous injection of anti CEA­-Alexa Fluor 488. Completeness of resection was assessed from postoperative imaging. Mice were followed postoperatively until premorbid to determine disease-free survival (DFS) and overall survival (OS). Complete resection was achieved in 92% of mice in the FGS group compared to 45.5% in the BLS group (p = 0.001). FGS resulted in a smaller postoperative tumor burden (p = 0.01). Cure rates with FGS compared to BLS improved from 4.5 to 40%, respectively (p = 0.01), and 1­year postoperative survival rates increased from 0% with BLS to 28% with FGS (p = 0.01). Median DFS increased from 5 weeks with BLS to 11 weeks with FGS (p = 0.0003). Median OS increased from 13.5 weeks with BLS to 22 weeks with FGS (p = 0.001). FGS resulted in greater cure rates and longer DFS and OS using a fluorophore-­conjugated anti ­CEA antibody. The present results demonstrate that FGS has potential to improve the surgical treatment of pancreatic cancer.

Citation Format: Cristina A. Metildi, Sharmeela Kaushal, George A. Luiken, Robert M. Hoffman, Michael Bouvet. Pancreatic cancer fluorescence-­guided surgery with a fluorophore­-conjugated antibody to carcinoembryonic antigen (CEA) improves surgical resection and increases disease-free and overall survival in orthotopic mouse models. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 216. doi:10.1158/1538-7445.AM2015-216

Photoimmunotherapy Inhibits Tumor Recurrence After Surgical Resection on a Pancreatic Cancer Patient-Derived Orthotopic Xenograft (PDOX) Nude Mouse Model

BACKGROUND

Photoimmunotherapy (PIT) uses a target-specific photosensitizer based on a near-infrared (NIR) phthalocyanine dye, IR700, to induce tumor necrosis after irradiation with NIR light to kill cancer cells, such as those that remain after surgery. The purpose of the present study was to sterilize the surgical bed after pancreatic cancer resection with PIT in carcinoembryonic antigen (CEA)-expressing, patient-derived, orthotopic xenograft (PDOX) nude mouse models.

METHODS

After confirmation of tumor engraftment, mice were randomized to two groups: bright light surgery (BLS)-only and BLS + PIT. Each treatment arm consisted of seven tumor-bearing mice. BLS was performed under standard bright-field with an MVX10 long-working distance, high-magnification microscope on all mice. For BLS + PIT, anti-CEA antibody conjugated with IR700 (anti-CEA-IR700) (50 µg) was injected intravenously in all mice 24 h before surgery. After the surgery, the resection bed was then irradiated with a red-light-emitting diode at 690 ± 5 nm with a power density of 150 mW/cm(2).

RESULTS

Anti-CEA-IR700 labelled and illuminated the pancreatic cancer PDOX. Minimal residual cancer of the PDOX was detected by fluorescence after BLS. The local recurrence rate was 85.7 % for BLS-only and 28.6 % for BLS + PIT-treated mice (p = 0.05). The average recurrent tumor weight was 1149.0 ± 794.6 mg for BLS-only and 210.8 ± 336.9 mg for BLS + PIT-treated mice (p = 0.015).

CONCLUSION

Anti-CEA-IR700 was able to label and illuminate a pancreatic cancer PDOX nude mouse model sufficiently for PIT. PIT reduced recurrence by eliminating remaining residual cancer cells after BLS.

Photoimmunotherapy lowers recurrence after pancreatic cancer surgery in orthotopic nude mouse models

BACKGROUND

Photoimmunotherapy (PIT) is based on the use of a monoclonal antibody specific to cancer epitopes conjugated to a photosensitizer near-infrared phthalocyanine dye (IR700). In this study, PIT with IR700 conjugated to anti-carcinoembryonic antigen (CEA) was used as an adjunct to surgery in orthotopically-implanted human pancreatic cancer in a nude mouse model to eliminate microscopic disease in the post-surgical tumor bed and prevent local as well as metastatic recurrence.

MATERIALS AND METHODS

Athymic nude mice were orthotopically implanted with the human pancreatic cancer cell line BxPC3 expressing green fluorescent protein. After tumor engraftment, the mice were divided into two groups as follows: bright light surgery (BLS) + anti-CEA-IR700 + 690 nm laser (PIT); and BLS only. Anti-CEA-IR700 (100 μg) was administered to the treatment group via tail-vein injection 24 h before therapy. Tumors were resected, and the surgical bed was treated with intraoperative phototherapy at an intensity of 150 mW/cm(2) for 30 min. Mice were imaged noninvasively for 8 wk using an OV-100 small animal fluorescence imager.

RESULTS

BLS + PIT reduced local recurrence to 1/7 mice from 7/7 mice with BLS-only (P = 0.001) and metastatic recurrence to 2/7 mice compared with 6/7 mice with BLS-only (P = 0.03). Local tumor growth continued at a rapid rate after BLS-only compared with BLS + PIT where almost no local growth occurred. There was a significant difference in tumor size between mice in the BLS + PIT (2.14 mm(2), 95% confidence interval [CI] [-2.06 to 6.34] and BLS-only groups (115.2 mm(2), 95% CI [88.8-141.6]) at 6 wk after surgery (P < 0.001). There was also a significant difference in tumor weight between the BLS + PIT group (6.65 mg, 95% CI [-6.35 to 19.65] and BLS-only group (1100 mg, 95% CI [794-1406] at 8 wk after surgery (P < 0.001).

CONCLUSIONS

PIT holds promise in the treatment of pancreatic cancer and may serve as a useful adjunct to surgery in the eradication of microscopic residual disease that can lead to both local and metastatic recurrence. Further studies are warranted to investigate the potential toxicities of PIT, especially with regard to anastomoses, such as those involved in pancreaticoduodenectomy.

Abstract 4306: Bioconjugation of near infrared dyes by PEGylation improves pharmacokinetics and allows for better labeling and imaging of human gastrointestinal cancers

NIR dyes are becoming increasingly popular due to their good tissue penetration, low tissue autofluorescence and resistance to hemoglobin quenching. However, they are still limited by lower hydrophilicity and poor chemical and photo-stability in-vivo. We aimed to try to improve these properties by covalent modification of these dyes by addition of polyethylene glycol (PEG) chains. We studied 2 commercially-available NIR dyes, DyLight 650 and 750, to evaluate how PEGylation affects the pharmacokinetics, biodistribution and imaging. PEGylated and non-PEGylated DyLight 650 and 750 dyes were conjugated to a chimeric anti-CEA antibody and were injected intravenously into nude mice. Serum samples were collected at various time points to determine serum concentrations and clearance kinetics. Biodistribution was determined by tissue sonication and analyzing tissue concentration profiles over time. PEGylated dyes had significantly higher serum concentrations than non-PEGylated dyes with p=0.005 for the 650 dyes and p&lt;0.001 for the 750 dyes. PEGylated dyes had significantly lower liver concentrations (p=0.03 for the 650 dyes; p=0.002 for the 750 dyes) and higher renal concentrations (p=0.003 for the 650 dyes and p&lt;0.001 for the 750 dyes) compared to non-PEGylated dyes. Human pancreatic tumors subcutaneously implanted into nude mice were labeled with antibody-dye conjugates and serially imaged. Labeling with PEGylated dyes resulted in significantly brighter tumors compared to the non-PEGylated dyes (p&lt;0.001 for the 650 dyes; p=0.01 for 750 dyes). In a liver metastasis model of colon cancer, PEGylated dyes showed bright labeling of metastatic tissue with good contrast between normal and malignant tissue. PEGylation of the NIR dyes DyLight 650 and 750 significantly changes their pharmacokinetics and biodistribution, allowing higher serum concentrations, longer half-life, brighter tissue labeling and decreased accumulation in lymphoid organs. This allows for high fidelity imaging of metastatic disease to any lymphoid or hemoglobin dense organ such as the liver.

Citation Format: Ali A. Maawy, Yukihiko Hiroshima, George A. Luiken, Yong Zhang, Robert M. Hoffman, Michael Bouvet. Bioconjugation of near infrared dyes by PEGylation improves pharmacokinetics and allows for better labeling and imaging of human gastrointestinal cancers. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4306. doi:10.1158/1538-7445.AM2014-4306

Abstract 4312: Seamless fluorescence guided surgery for pancreatic cancer is facilitated by a hand held electrocautery pencil with excitation light source

Fluorescent labeling of tumors with the goal of fluorescence guided surgical resection (FGS) continues to be perfected and investigated. In addition to a bright fluorophore that specifically and selectively labels tumor tissue, a specific excitation light source that can be turned on as needed by the surgeon without having to take their hands off the dissecting instruments would be the most ideal system. The optimal method for tissue excitation would therefore require the excitation light source to be on the surgeon's dissecting or cutting instrument that could be easily turned on or off as needed and in direct line with the labeled tumor tissue. In designing the excitation light source we decided to use the NIR window (600-1000 nm) due to it's favorable imaging qualities that would allow for fluorophore excitation without the necessity of eliminating white light from the field and with little to no tissue autofluorescence. An electrocautery pencil was fitted with LEDs at the base of the tip with an emitted signal between 633-660nm. The complementary dye selected for labeling was DyLight 650 (Ex: 652 nm, Em: 672 nm). Nude mice were implanted with patient-derived orthotopic xenograft (PDOX) pancreatic tumors and allowed 4 weeks for engraftment. Anti-CA 19-9 antibody was then conjugated to DyLight 650 and injected intravenously 24 hours prior to FGS. After 24 hours the mice underwent surgical exploration for an attempt at FGS with the new device. A Canon EOS 60D camera fitted with a 672 nm emission filter connected to a 19 inch monitor was selected as the fluorescence image-capturing device. The mice were grounded appropriately to a surgical monopolar generator selected to power to the electrocautery pencil. After initial incision and tumor exposure under bright light the tumor was illuminated by the excitation LEDs by simply pushing forward on the cautery activation button on the device. The fluorescently labeled image of the tumor was easily seen and confirmed on the monitor in real-time as the surgery proceeded. The tumor was brightly visible with good background contrast. Using this method had the benefit of allowing tumor resection with electrocautery using both ambient light and the fluorescent image simultaneously to confirm a complete resection. In this respect, critical surrounding structures are visible with the ambient light, helping to avoid inadvertent tissue injury. Coupling an excitation LED light source to an electrocautery pencil allows for good imaging of pre-labeled tumors during resection without mounting an external excitation light source. The set-up is very compact, efficient, easy to sterilize and works very efficiently during surgical resection without the need to eliminate background light. This is highly advantageous and allows simultaneous visualization of the surgical field in white light and the labeled tumor via an imaging device connected to a monitor.

Citation Format: Ali A. Maawy, Yukihiko Hiroshima, George A. Luiken, Yong Zhang, Richard P. Fleenor, Robert M. Hoffman, Michael Bouvet. Seamless fluorescence guided surgery for pancreatic cancer is facilitated by a hand held electrocautery pencil with excitation light source. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4312. doi:10.1158/1538-7445.AM2014-4312

Polyethylene glycol (PEG) linked to near infrared (NIR) dyes conjugated to chimeric anti-carcinoembryonic antigen (CEA) antibody enhances imaging of liver metastases in a nude-mouse model of human colon cancer

We report here that polyethylene glycol (PEG) linked to near infrared dyes conjugated to chimeric mouse-human anti-carcinoembryonic antigen (CEA) antibody greatly improves imaging of liver metastases in a nude mouse model of colon-cancer experimental metastases. PEGylated and non-PEGylated DyLight 650 and 750 dyes were conjugated to the chimeric anti-CEA antibody. The dyes were initially injected intravenously into nude mice without tumors. Tissue biodistribution was determined by tissue sonication and analyzing tissue dye concentration profiles over time. PEGylated dyes had significantly lower accumulation in the liver (p = 0.03 for the 650 dyes; p = 0.002 for the 750 dyes) compared to non-PEGylated dyes. In an experimental liver metastasis model of HT-29 colon cancer, PEGylated dyes conjugated to the anti-CEA antibody showed good labeling of metastatic tumors with high contrast between normal and malignant tissue which was not possible with the non-PEGylated dyes since there was so much non-specific accumulation in the liver. PEGylation of the DyLight 650 and 750 NIR dyes significantly altered tissue biodistribution, allowing brighter tissue labeling, decreased accumulation in normal organs, particularly the liver. This enabled high fidelity and high contrast imaging of liver metastases.

Fluorescence-guided surgery with a fluorophore-conjugated antibody to carcinoembryonic antigen (CEA), that highlights the tumor, improves surgical resection and increases survival in orthotopic mouse models of human pancreatic cancer

BACKGROUND

We have developed a method of distinguishing normal tissue from pancreatic cancer in vivo using fluorophore-conjugated antibody to carcinoembryonic antigen (CEA). The objective of this study was to evaluate whether fluorescence-guided surgery (FGS) with a fluorophore-conjugated antibody to CEA, to highlight the tumor, can improve surgical resection and increase disease-free survival (DFS) and overall survival (OS) in orthotopic mouse models of human pancreatic cancer.

METHODS

We established nude-mouse models of human pancreatic cancer with surgical orthotopic implantation of the human BxPC-3 pancreatic cancer. Orthotopic tumors were allowed to develop for 2 weeks. Mice then underwent bright-light surgery (BLS) or FGS 24 h after intravenous injection of anti-CEA-Alexa Fluor 488. Completeness of resection was assessed from postoperative imaging. Mice were followed postoperatively until premorbid to determine DFS and OS.

RESULTS

Complete resection was achieved in 92 % of mice in the FGS group compared to 45.5 % in the BLS group (p = 0.001). FGS resulted in a smaller postoperative tumor burden (p = 0.01). Cure rates with FGS compared to BLS improved from 4.5 to 40 %, respectively (p = 0.01), and 1-year postoperative survival rates increased from 0 % with BLS to 28 % with FGS (p = 0.01). Median DFS increased from 5 weeks with BLS to 11 weeks with FGS (p = 0.0003). Median OS increased from 13.5 weeks with BLS to 22 weeks with FGS (p = 0.001).

CONCLUSIONS

FGS resulted in greater cure rates and longer DFS and OS using a fluorophore-conjugated anti-CEA antibody. FGS has potential to improve the surgical treatment of pancreatic cancer.

Specific tumor labeling enhanced by polyethylene glycol linkage of near infrared dyes conjugated to a chimeric anti-carcinoembryonic antigen antibody in a nude mouse model of human pancreatic cancer

Labeling of metastatic tumors can aid in their staging and resection of cancer. Near infrared (NIR) dyes have been used in the clinic for tumor labeling. However, there can be a nonspecific uptake of dye by the liver, lungs, and lymph nodes, which hinders detection of metastasis. In order to overcome these problems, we have used two NIR dyes (DyLight 650 and 750) conjugated to a chimeric anti-carcinoembryonic antigen antibody to evaluate how polyethylene glycol linkage (PEGylation) can improve specific tumor labeling in a nude mouse model of human pancreatic cancer. The conjugated PEGylated and non-PEGylated DyLight 650 and 750 dyes were injected intravenously into non-tumor-bearing nude mice. Serum samples were collected at various time points in order to determine serum concentrations and elimination kinetics. Conjugated PEGylated dyes had significantly higher serum dye concentrations than non-PEGylated dyes (p=0.005 for the 650 dyes and p<0.001 for the 750 dyes). Human pancreatic tumors subcutaneously implanted into nude mice were labeled with antibody-dye conjugates and serially imaged. Labeling with conjugated PEGylated dyes resulted in significantly brighter tumors compared to the non-PEGylated dyes (p<0.001 for the 650 dyes; p=0.01 for 750 dyes). PEGylation of the NIR dyes also decreased their accumulation in lymph nodes, liver, and lung. These results demonstrate enhanced selective tumor labeling by PEGylation of dyes conjugated to a tumor-specific antibody, suggesting their future clinical use in fluorescence-guided surgery.

Comparison of a chimeric anti-carcinoembryonic antigen antibody conjugated with visible or near-infrared fluorescent dyes for imaging pancreatic cancer in orthotopic nude mouse models

The aim of this study was to evaluate a set of visible and near-infrared dyes conjugated to a tumor-specific chimeric antibody for high-resolution tumor imaging in orthotopic models of pancreatic cancer. BxPC-3 human pancreatic cancer was orthotopically implanted into pancreata of nude mice. Mice received a single intravenous injection of a chimeric anti-carcinoembryonic antigen antibody conjugated to one of the following fluorophores: 488-nm group (Alexa Fluor 488 or DyLight 488); 550-nm group (Alexa Fluor 555 or DyLight 550); 650-nm group (Alexa Fluor 660 or DyLight 650), or the 750-nm group (Alexa Fluor 750 or DyLight 755). After 24 h, the Olympus OV100 small-animal imaging system was used for noninvasive and intravital fluorescence imaging of mice. Dyes were compared with respect to depth of imaging, resolution, tumor-to-background ratio (TBR), photobleaching, and hemoglobin quenching. The longer wavelength dyes had increased depth of penetration and ability to detect the smallest tumor deposits and provided the highest TBRs, resistance to hemoglobin quenching, and specificity. The shorter wavelength dyes were more photostable. This study showed unique advantages of each dye for specific cancer imaging in a clinically relevant orthotopic model.

Fluorescently labeled chimeric anti-CEA antibody improves detection and resection of human colon cancer in a patient-derived orthotopic xenograft (PDOX) nude mouse model

BACKGROUND AND OBJECTIVES

The aim of this study was to evaluate a new fluorescently labeled chimeric anti-CEA antibody for improved detection and resection of colon cancer.

METHODS

Frozen tumor and normal human tissue samples were stained with chimeric and mouse antibody-fluorophore conjugates for comparison. Mice with patient-derived orthotopic xenografts (PDOX) of colon cancer underwent fluorescence-guided surgery (FGS) or bright-light surgery (BLS) 24 hr after tail vein injection of fluorophore-conjugated chimeric anti-CEA antibody. Resection completeness was assessed using postoperative images. Mice were followed for 6 months for recurrence.

RESULTS

The fluorophore conjugation efficiency (dye/mole ratio) improved from 3-4 to >5.5 with the chimeric CEA antibody compared to mouse anti-CEA antibody. CEA-expressing tumors labeled with chimeric CEA antibody provided a brighter fluorescence signal on frozen human tumor tissues (P = 0.046) and demonstrated consistently lower fluorescence signals in normal human tissues compared to mouse antibody. Chimeric CEA antibody accurately labeled PDOX colon cancer in nude mice, enabling improved detection of tumor margins for more effective FGS. The R0 resection rate increased from 86% to 96% with FGS compared to BLS.

CONCLUSION

Improved conjugating efficiency and labeling with chimeric fluorophore-conjugated antibody resulted in better detection and resection of human colon cancer in an orthotopic mouse model.

Abstract 729: Chimeric antibodies to tumor antigen CEA improve detection of human colon cancer for fluorescence-guided surgery

Mouse models of human colon cancer were established with fragments of a CEA-expressing patient colon tumor. Mice received tail vein injections of a human-mouse chimeric anti-CEA-Alexa-488 antibody or mouse anti-CEA-Alexa-488 antibody 24 hours prior to fluorescence-guided surgery (FGS). Pre- and post-operative images were obtained to assess for completeness of resection. Mice were subsequently followed for 6 months post-operatively to assess for tumor recurrence and overall survival. At termination, all tumor lesions were harvested and evaluated histologically. Furthermore, the chimeric antibody was tested on frozen tumor and normal tissue arrays comparing it to the mouse antibody. The chimeric antibody demonstrated improved sensitivity and specificity in labeling the CEA-expressing tumor compared to the mouse antibody. The conjugation efficiency of the fluorophore to the chimeric antibody was 2-fold higher than that of the mouse antibody. On frozen tumor tissue arrays, the signal intensity of the chimeric antibody was significantly brighter compared to the mouse antibody indicating improved binding to tumor tissue. The chimeric antibody demonstrated improved specificity as shown by the lower signal intensity in normal human tissue samples compared to the mouse antibody indicating decreased binding of the chimeric antibody. The animals injected with the chimeric antibody had more effective FGS than the animals injected with the mouse antibody indicating improved visualization of tumor margins by the chimeric antibody. The humanized chimeric antibody has greater potential for clinical application for FGS than a mouse antibody.

Citation Format: Cristina A. Metildi, Sharmeela Kaushal, George A. Luiken, Robert M. Hoffman, Michael Bouvet. Chimeric antibodies to tumor antigen CEA improve detection of human colon cancer for fluorescence-guided surgery. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 729. doi:10.1158/1538-7445.AM2013-729

Abstract 4138: Fluorescence laparoscopy with an LED light source enables fluorescence-guided resection of pancreatic cancer, labeled with fluorophore-conjugated antibodies, in mouse models

Orthotopic mouse models of human pancreatic cancer were established with the BxPC-3 RFP pancreatic cancer cell line. Two weeks after implantation, mice were randomized to undergo bright light laparoscopic resection (BLR) (n=19) or fluorescence-guided laparoscopic resection (FLR) (n=19). Fluorescence laparoscopy was performed with a 495-nm emission filter and a Stryker L9000 LED light source 24 hours after tail vein injection of anti-CEA-Alexa 488 antibodies. Bright light laparoscopy was performed with a Stryker X8000 xenon light source. Pre- and postoperative images were taken with the Olympus OV-100 Small Animal Imaging System to assess completeness of resection. Postoperatively, whole body images were obtained to assess for recurrence and follow tumor progression. Intravital and ex vivo images were obtained at termination to evaluate tumor burden. FLS enabled real-time identification and localization of brightly-fluorescent BxPC-3 RFP tumor labeled with anti-CEA-Alexa 488. Furthermore, there was adequate background illumination for surgical navigation permitting improved resection. At termination at 12 weeks, mice in the FLS group had a smaller pancreatic tumor burden compared to mice from the BLS group (5.75 mm2 vs 28.43 mm2; p=0.012). Mice in the FLS group also experienced decreased local recurrence (47.4% vs 78.9%, p=0.046) and distant recurrence (68.4% vs 94.7%, p=0.045) compared to mice in the BLS group. Fluorescence-guided surgery has significant potential to improve laparoscopic approaches in the treatment of pancreatic cancer.

Citation Format: Cristina A. Metildi, Sharmeela Kaushal, George A. Luiken, Mark A. Talamini, Robert M. Hoffman, Michael Bouvet. Fluorescence laparoscopy with an LED light source enables fluorescence-guided resection of pancreatic cancer, labeled with fluorophore-conjugated antibodies, in mouse models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4138. doi:10.1158/1538-7445.AM2013-4138

Abstract 726: Fluorophore-conjugated antibodies improve surgical resection of pancreatic cancer leading to prolonged disease-free survival and overall survival in orthotopic mouse models

We established orthotopic mouse models of human pancreatic cancer with fragments of BxPC-3-RFP tumor. Two weeks after implantation, mice were randomized to FGS or bright-field surgery (BS). FGS was performed 24 hrs after tail vein injection of anti-CEA-Alexa 488. Completeness of resection was assessed from pre- and postoperative images obtained with the OV-100 Small Animal Imaging System. Whole body images of mice were obtained postoperatively to assess for recurrence and mice were followed until premorbid to measure survival. We achieved a complete resection of pancreatic cancers in 92% of mice in the FGS group as compared to 58% in the BS group (p=0.002). Preoperative tumor burden was not significantly different between groups (p=0.424). However, FGS afforded a significantly smaller mean postoperative tumor burden compared to BS: 0.0004 ± SE 0.0003 mm2 vs. 0.0841 ± SE 0.027 mm2, p=0.004. On average, mice in the FGS experienced a greater reduction in tumor burden: 99.99% vs 97.72%, p=0.01. FGS reduced recurrence rates from 95% to 50% (p=0.002) and lengthened mean disease-free survival from 7 weeks to 30.5 weeks (p&lt;0.001). The FGS group experienced longer overall survival compared to the BS group: 16.5 weeks vs. 37 weeks (p=0.001). Cure rate was improved with FGS from 5% to 50% (p=0.003). Furthermore, FGS more than doubled the one-year postoperative survival rate from 3 mice in the BLS group to 8 mice in the FGS group (p=0.005). This novel approach has potential to improve outcomes in the surgical treatment of pancreatic cancer.

Survival and recurrence according to surgical mode. Surgical Mode Disease-Free Survival Overall Survival Recurrence Rate Bright-Field Surgery 7 weeks 16.5 weeks 95% Fluorescence-Guided Surgery 30.5 weeks 37 weeks 50%

Citation Format: Cristina A. Metildi, Sharmeela Kaushal, Mark A. Talamini, George A. Luiken, Robert M. Hoffman, Michael Bouvet. Fluorophore-conjugated antibodies improve surgical resection of pancreatic cancer leading to prolonged disease-free survival and overall survival in orthotopic mouse models. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 726. doi:10.1158/1538-7445.AM2013-726

Tumor-specific fluorescence antibody imaging enables accurate staging laparoscopy in an orthotopic model of pancreatic cancer

BACKGROUND/AIMS

Laparoscopy is important in staging pancreatic cancer, but false negatives remain problematic. Making tumors fluorescent has the potential to improve the accuracy of staging laparoscopy.

METHODOLOGY

Orthotopic and carcinomatosis models of pancreatic cancer were established with BxPC-3 human pancreatic cancer cells in nude mice. Alexa488-antiCEA conjugates were injected via tail vein 24 hours prior to laparoscopy. Mice were examined under bright field laparoscopic (BL) and fluorescence laparoscopic (FL) modes. Outcomes measured included time to identification of primary tumor for the orthotopic model and number of metastases identified within 2 minutes for the carcinomatosis model.

RESULTS

FL enabled more rapid and accurate identification and localization of primary tumors and metastases than BL. Using BL took statistically significantly longer time than FL (p<0.0001, fold change and 95% CI for BL vs. FL: 8.12 (4.54,14.52)). More metastatic lesions were detected and localized under FL compared to BL and with greater accuracy, with sensitivities of 96% vs. 40%, respectively, when compared to control. FL was sensitive enough to detect metastatic lesions <1mm.

CONCLUSIONS

The use of fluorescence laparoscopy with tumors labeled with fluorophore-conjugated anti-CEA antibody permits rapid detection and accurate localization of primary and metastatic pancreatic cancer in an orthotopic model. The results of the present report demonstrate the future clinical potential of fluorescence laparoscopy.

An LED light source and novel fluorophore combinations improve fluorescence laparoscopic detection of metastatic pancreatic cancer in orthotopic mouse models

BACKGROUND

The aim of this study was to improve fluorescence laparoscopy of pancreatic cancer in an orthotopic mouse model with the use of a light-emitting diode (LED) light source and optimal fluorophore combinations.

STUDY DESIGN

Human pancreatic cancer models were established with fluorescent FG-RFP, MiaPaca2-GFP, BxPC-3-RFP, and BxPC-3 cancer cells implanted in 6-week-old female athymic mice. Two weeks postimplantation, diagnostic laparoscopy was performed with a Stryker L9000 LED light source or a Stryker X8000 xenon light source 24 hours after tail-vein injection of CEA antibodies conjugated with Alexa 488 or Alexa 555. Cancer lesions were detected and localized under each light mode. Intravital images were also obtained with the OV-100 Olympus and Maestro CRI Small Animal Imaging Systems, serving as a positive control. Tumors were collected for histologic analysis.

RESULTS

Fluorescence laparoscopy with a 495-nm emission filter and an LED light source enabled real-time visualization of the fluorescence-labeled tumor deposits in the peritoneal cavity. The simultaneous use of different fluorophores (Alexa 488 and Alexa 555), conjugated to antibodies, brightened the fluorescence signal, enhancing detection of submillimeter lesions without compromising background illumination. Adjustments to the LED light source permitted simultaneous detection of tumor lesions of different fluorescent colors and surrounding structures with minimal autofluorescence.

CONCLUSIONS

Using an LED light source with adjustments to the red, blue, and green wavelengths, it is possible to simultaneously identify tumor metastases expressing fluorescent proteins of different wavelengths, which greatly enhanced the signal without compromising background illumination. Development of this fluorescence laparoscopy technology for clinical use can improve staging and resection of pancreatic cancer.

Abstract 366: Enhanced tumor detection of fluoroscence laparoscopy improves laparoscopic resection of primary pancreatic cancer in mouse models

The aim of this study was to evaluate the utility of fluorescence laparoscopy for resection of primary pancreatic cancer. Orthotopic mouse models of human pancreatic cancer were established with the brightly-fluorescent BxPC-3 RFP human pancreatic cancer cell line. Two weeks after implantation, mice were randomized to undergo either bright light laparoscopic resection (BLR) or fluorescence-guided laparoscopic resection (FLR). Fluorescence laparoscopy (FL) was performed with a Stryker L9000 LED light source 24 hours after tail vein injection of CEA antibodies conjugated to Alexa 488. Bright light laparoscopy (BL) was performed with a Stryker X8000 xenon light source. Pre- and postoperative images were taken with the Olympus OV-100 Small Animal Imaging System to assess completeness of resection. Postoperatively, whole body images were obtained to assess for recurrence and follow tumor progression. All resected tumors were collected for histologic review. Fluorescence laparoscopy with a 495-nm emission filter and an LED light source enabled real-time identification and localization of the brightly-fluorescent BxPC-3 RFP tumor additionally labeled with anti-CEA-Alexa 488. The combination of red and green fluorophores optimized the fluorescence signal of the tumor thereby enabling accurate distinction of tumor margins from normal surrounding tissue without compromising background illumination. Furthermore, adequate visualization of surrounding structures enabled surgical navigation for resection of primary pancreatic tumor. Tumor was more readily detected and resected under fluorescence guidance than under standard bright light. In addition, sub-millimeter lesions within the pancreas that were undetected by bright light laparoscopy were easily identified and resected by fluorescence laparoscopy. This study demonstrates the capabilities of laparoscopic fluorescence-guided surgery of primary pancreatic cancer. The optimal combination of fluorophores with the use of an LED light source enhanced the fluorescence tumor-to-background ratio while permitting enough light leakage for background illumination for surgical navigation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 366. doi:1538-7445.AM2012-366

Abstract 369: Tumor detection and surgical navigation with fluorescence laparoscopy is enhanced with combinations of differently labeled fluorophore-conjugated antibodies and fluorescent proteins

The aim of this study was to improve detection of primary and metastatic lesions of human pancreatic cancer in mouse models with fluorescence laparoscopy by enhancing the fluorescence signal of tumor with different combinations of fluorophores without compromising background illumination. Human pancreatic cancer models were established with combinations of FG-RFP, MiaPaca2-GFP, BxPC-3-RFP, or BxPC-3 cancer cells implanted in 6-week-old female athymic mice. Two weeks post-implantation, diagnostic laparoscopy was performed with a Stryker L9000 LED light source 24 hours after tail vein injection of CEA antibodies conjugated with Alexa 488- and/or Alexa 555. Cancer lesions were detected and localized under the fluorescence light mode. Intravital images were obtained with the Maestro CRI Small Animal Imaging System, serving as a positive control. Tumors were collected for histologic review. Fluorescence laparoscopy with a 495-nm emission filter and an LED light source enabled real-time visualization of differently fluorescence-labeled tumors in the peritoneal cavity simultaneously. The combination of BxPC-3 RFP labeled with anti-CEA-Alexa 488 afforded the brightest signal of all established mouse models. We were able to reproduce this enhanced fluorescence signaling by doubly labeling non-color BxPC-3 tumor with anti-CEA-Alexa 488 and anti-CEA-Alexa 555. The doubly labeled tumor provided a greater signal intensity profile compared to tumors labeled with either anti-CEA-Alexa 488 or -Alexa 555 alone. This enhanced fluorescence signal permitted improved detection of sub-millimeter lesions without compromising background illumination. The ability to visualize tumor deposits expressing fluorescent proteins of different wavelengths simultaneously with an LED light source enabled us to establish the optimal combination of fluorophores that enhanced the signal intensity of fluorescence. With this optimal fluorophore combination, we improved the detection of sub-millimeter tumor lesions without impairing the visualization of surrounding structures necessary for surgical navigation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 369. doi:1538-7445.AM2012-369

Use of high-resolution fluorescence laparoscopy with fluorophore-conjugated tumor-specific antibodies for the detection of pancreatic cancer metastasis invisible with standard laparoscopy

212

Background: Standard laparoscopy for pancreatic cancer often leads to false negative results, causing understaging of the disease. Improved sensitivity and resolution are necessary.

Methods: Orthotopic and carcinomatosis mouse models of human pancreatic cancer were established with red fluorescent protein (RFP)-expressing or non-fluorescent BxPC-3 human pancreatic cancer cells. The mice with orthotopic unlabeled pancreatic cancer were administered Alexa 488- or 555-conjugated anti-CEA by tail-vein injection 2-4 weeks after tumor implantation. Diagnostic laparoscopy was performed with a Stryker L9000 LED light source or X8000 xenon light source 24 hours later. Pancreatic tumors were detected and localized under each light mode. After laparoscopy, intravital images were obtained with the OV-100 and Maestro CRI Small Animal Imaging Systems as positive controls. Tumors were collected for histologic analysis.

Results: Fluorescence laparoscopy (FL) with the use of 495-nm excitation filter and an LED light source enabled more rapid and accurate identification and localization of primary tumors and metastases than bright light laparoscopy (BL). The use of fluorescent conjugates antibody-labeled tumors improved the accuracy of staging laparoscopy, increasing the sensitivity from 40% in BL to 96% in FL (p<0.001). FL was sufficiently sensitive to detect sub-millimeter tumor deposits that went undetected under BL. With adjustments to the LED light source, we could simultaneously detect tumor lesions of different fluorescent colors and surrounding structures with minimal autofluorescence.

Conclusions: The use of FL and fluorophore-labeled anti-CEA antibodies permits rapid detection and accurate localization of primary and metastatic CEA-expressing human pancreatic cancer, including tumors that were undetectable with BL. The introduction of an LED light source allows simultaneous identification of fluorescent tumor of different wavelengths without compromising background illumination. Further development of this technology for clinical use can improve the staging and treatment of pancreatic cancer.

Abstract 5323: Staging of metastatic pancreatic cancer is facilitated by fluorescence laparoscopy

The aim of this report was to improve the real-time imaging of fluorescence laparoscopy with the introduction of an LED light source. We also attempted to determine the optimal fluorophore to improve accurate identification and localization of tumor deposits without the loss of background illumination. Human pancreatic cancer orthotopic models were established with intraperitoneal injections of RFP-expressing FG or BxPC-3, or non-fluorescent BxPC-3 human pancreatic cancer cells into 6-week-old female athymic mice. One to 2 weeks post implantation, diagnostic laparoscopy was performed with a Stryker L9000 LED light source or a Stryker X8000 xenon light source 24 hours after tail vein injection of Alexa 488-conjugated anti-CEA. An attempt was made to detect and localize all cancer lesions under each light mode. After laparoscopy, the animals were sacrificed and abdominal cavities exposed. Images of the lesions were obtained with the Maestro CRI Small Animal Imaging System serving as a positive control. Tumors were collected and processed for histologic review. Fluorescence laparoscopy with the use of a 495-nm emission filter and an LED light source enabled real-time visualization of the fluorescence-labeled tumor metastases in the peritoneal cavity. With adjustments to the LED light source, we could simultaneously detect tumor lesions of different fluorescent colors and surrounding structures with minimal autofluorescence. Overall, fluorescence laparoscopy using the LED light source afforded accurate detection of more lesions compared to standard xenon bright field laparoscopy. In addition, several tumor deposits of less than 1mm were identified and localized under FL. Such lesions were not detected under bright field laparoscopy. All identified lesions, when possible, were verified histologically. In this study, we have thus demonstrated that using an LED light source with adjustments to the red, blue and green wavelengths, we can simultaneously identify fluorescent tumor metastases of different wavelengths without compromising background illumination. The further development of this technology can serve as a novel tool in the staging and treatment of pancreatic cancer.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5323. doi:10.1158/1538-7445.AM2011-5323

In vivo fluorescence of medullary carcinoma of the thyroid: a technology with potential to improve visualization of malignant tissue at surgical resection

Medullary carcinoma of the thyroid requires aggressive treatment because of its potential to metastasize and because of the current limitations of preoperative localization and systemic therapy. If these tumors could be made to fluoresce in vivo with tagged fluorophore antibodies against tumor antigens, surgeons would be able to obtain additional information in the operating room to facilitate a more complete resection. Based on the success of our previous work in breast and colon cancer models, we conducted an animal study of in vivo tumor fluorescence of a human medullary thyroid cell line in which bright tumor fluorescence is visible during dissection. To accomplish this, we used an inexpensive and commercially available handheld, blue (470 nm), light-emitting diode flashlight and filtered goggles (520 nm). This procedure, which we call the fluorescent antibody-assisted surgical technique (FAAST), is easy to perform, requires no complex or expensive technical equipment, and has the potential to be applied to a wide variety of tumors. To the best of our knowledge, this is the first experiment of its kind to be reported in the literature.

The Groshong catheter: initial experience and early results of imaging-guided placement

Fifty Groshong catheters were placed in 50 patients with use of ultrasound (US) and fluoroscopic guidance in the radiology suite: 49 were placed via the subclavian vein and one was placed via the left internal jugular vein. All (100%) attempts at catheter placement were successful. Imaging guidance affected the placement of catheters in 12 cases (24%), including four patients (8%) in whom vascular access would not have been possible with blinded percutaneous venipuncture or surgical cutdown. After a four-case learning curve period, during which one pneumothorax (2%) and two arterial punctures (4%) occurred, there were no further venipuncture-related complications. One catheter was removed because of infection (2%) and one because of allergic reaction (2%) to the antimicrobial cuff. Four patients with cutaneous infections and one with catheter-related sepsis were successfully treated with antibiotics. Results demonstrate the initial promise of imaging-guided placement of central venous access catheters when performed in the radiology suite.

Clinical manifestations of essential thrombocythemia in young adults

Essential thrombocythemia (ET) is a myeloproliferative disorder characterized by isolated overproduction of platelets, thrombohemorrhagic complications, and a median age of 50-60. When it occurs in younger patients, the incidence of complications has been reported to be quite low, with a good long-term prognosis. We report a retrospective review of 13 patients with ET between the ages of 22 and 35 in which 11 were symptomatic at diagnosis, with only one remaining asymptomatic during follow-up. Three patients presented with potentially life-threatening complications (two myocardial infarctions, one stroke), although no deaths were observed. The majority of the nonlife-threatening complications were vaso-occlusive in nature, including erythromelalgia and transient neurologic symptoms. We conclude that ET in young adults is not always a benign disease and that potentially life-threatening complications are not rare. The optimum approach to treatment in this or any other age group remains uncertain.

Hematologic evaluation of employees with leukopenia. Naval Weapons Center, China Lake, California

Evaluation of 86 employees with a history of leukopenia at the Naval Weapons Center (NWC), China Lake, California, was done by exposure questionnaires, medical histories, physical examinations, peripheral blood smear, and bone marrow evaluations, including morphologic examination, stem cell culture, and cytogenetics. Forty-eight subjects were found to be leukopenic at the time of the study, and two subjects were found to have hairy cell leukemia. All subjects had positive exposure histories and were healthy at the time of the study. Review of peripheral smears identified the patients with marrow abnormalities. Bone marrow cultures revealed several patients with possible marrow suppression. Chromosome studies were not diagnostic. Five-year follow-up health questionnaires revealed no significant health problems; the two workers with hairy cell leukemia are alive and fully functional. Leukopenia in itself does not appear to be a risk factor for poor health, and it is unknown whether or not it may be a useful screening tool to identify workers at risk in toxic environments. Careful evaluation of blood cell counts and peripheral smears should be sufficient to identify people with potential marrow abnormalities.

Antibody against megakaryocytes in idiopathic thrombocytopenic purpura

Purified human IgG from both serum and the culture of human splenic cells was radiolabeled with 125I. Incubation of radiolabeled IgG from patients with idiopathic thrombocytopenic purpura (ITP) with normal homologous platelets or bone marrow cells resulted in significant (P less than .001) binding when compared with control IgG. Radioautographs showed that the radioactivity was associated with the platelets or megakaryocytes. The antiplatelet antibody in ITP has specificity for antigens associated with both platelets and megakaryocytes and suggests that thrombopolesis may also be affected in this disease.

Platelet-associated IgG in immune thrombocytopenic purpura

A method for the measurement of immunoglobulin G associated with gel-filtered platelets is described and finding in 70 control subjects and 37 patients with immune thrombocytopenic purpura (ITP) are reported. Control platelet-associated IgG (PAIgG) levels (nanograms IgG per 10(9) platelets) averaged (+/-SD) 1231+/-424; samples studied after 24 and 48 hr remained within the control range. PAIgG values of 19 adult and 12 childhood patients with chronic ITP averaged 4711+/-3025 and 4923+/-3955, respectively, and differed significantly from controls (p less than 0.001). There was an inverse correlation between PAIgG values and the chronic ITP patient's platelet count. Six patients with childhood acute ITP had PAIgG levels ranging from 5588 to 56,250 and appeared to represent a different statistical population from those with chronic ITP. In chronic ITP patients responding to splenectomy, there was an immediate normalization of PAIgG levels; however, a certain percentage of patients studied several months after splenectomy evidenced elevated PAIgG levels in association with normal platelet counts. These data showed that the direct measurement of platelet associated antibody is a useful technique in the diagnosis and follow-up of patients with chronic ITP. Preliminary studies in patients with acute ITP have suggested that this method may be useful in differentiating acute and chronic childhood ITP.