Use of contrast-enhanced ultrasound imaging with microbubbles targeted to αvβ3 integrins to enhance detection of early-stage ovarian tumors.

Abstract

5076 Background: Lack of an early detection test makes ovarian cancer (OVCA) a lethal gynecological malignancy. Tumor associated neo-angiogenesis (TAN) is an early event in tumor development and represents a potential target for early detection. Traditional transvaginal ultrasound (TVUS) cannot detect TAN at early stage. The goal of this pilot study was to examine the enhancement of TVUS using αvβ3 integrins targeted microbubble ultrasound contrast agent (UCA) in laying hens, a preclinical spontaneous model of human OVCA. Methods: 3-4 years old hens (n=50) were selected randomly and scanned continuously by TVUS before, during and after UCA (Visister-integrins, Targeson Inc. CA) injection at brachial veins. UCA was visualized using a low mechanical index contrast imaging pulse sequence. All pre- and post-contrast injection images were archived and analyzed off-line. Gross diagnosis was recorded at euthanasia and tissues were processed for histology. Tumors and their types were confirmed by routine histology. TAN markers (SMA and αvβ3 integrins) were detected by immunohistochemistry. TAN vessels were counted and correlation with ultrasound prediction was examined. Results: αvβ3-integrins targeted UCA enhanced the visualization of ovarian tumors significantly in laying hens. At gray scale, UCA bounded areas appeared as a ring on the ovarian surfaces of 8 of 50 hens and were suspected for ovarian tumors. Tumors were confirmed in all hens predicted to have OVCA. In 7 hens tumors were early stage and in one hen the tumor metastasized to the oviduct. A microscopic lesion was found in one hen which was not detected by ultrasound imaging. Thus 9 of 50 hens had ovarian tumors and UCA detected approximately 88% at early stages. The frequency of immunopositive TAN vessels (SMA and αvβ3 integrins positive) were significantly higher in OVCA hens than normal hens (P<0.05) and was positively correlated (0.86, P< 0.05) with ultrasound prediction. Conclusions: Our results demonstrate that UCA targeting αvβ3 integrin enhanced TVUS detection of early stage ovarian tumors in a pre-clinical model and may form the foundation for a clinical study. Support: Department of Defense (#09-3303), Sramek Foundation.