Earlier Detection of Breast Cancer with Ultrasound Molecular Imaging in a Transgenic Mouse Model

Abstract

While there is an increasing role of ultrasound for breast cancer screening in patients with dense breast, conventional anatomical-ultrasound lacks sensitivity and specificity for early breast cancer detection. In this study we assessed the potential of molecular-ultrasound imaging, using clinically-translatable vascular endothelial growth factor receptor (VEGFR2)-targeted microbubbles (MBVEGFR2), to improve the diagnostic accuracy of ultrasound in earlier detection of breast cancer and ductal carcinoma in situ (DCIS) in a transgenic mouse model (FVB/N-Tg(MMTV-PyMT)634Mul). In vivo binding specificity studies (n=26 tumors) showed that ultrasound imaging signal was significantly higher (P<0.001) using MBVEGFR2 compared to non-targeted microbubbles and imaging signal significantly decreased (P<0.001) by blocking antibodies. Ultrasound molecular imaging signal significantly increased (P<0.001), when breast tissue (n=315 glands) progressed from normal (1.65±0.17 a.u.) to hyperplasia (4.21±1.16), DCIS (15.95±1.31) and invasive cancer (78.1±6.31) and highly correlated with ex vivo VEGFR2 expression (R2=0.84; 95% CI, 0.72, 0.91; P<0.001). At an imaging signal threshold of 4.6 a.u., ultrasound molecular imaging differentiated benign from malignant entities with a sensitivity of 84% (95% CI, 78, 88) and specificity of 89% (95% CI, 81, 94). In a prospective screening trail (n=63 glands) diagnostic performance of detecting DCIS and breast cancer was assessed and two independent readers correctly diagnosed malignant disease in >95% of cases and highly agreed between each other (ICC=0.98; 95% CI, 97, 99). These results suggest that VEGFR2-targeted ultrasound molecular imaging allows highly accurate detection of DCIS and breast cancer in transgenic mice and may be a promising approach for early breast cancer detection in women.

High-frequency Ultrasound Imaging of Mouse Cervical Lymph Nodes

“…HFUS has been used to visualize diseased mouse lymph nodes within the main body cavity, demonstrating parallel utility of this technology to clinical practice. In particular, inflammatory and metastatic visceral lymph node alterations have been observed in mouse models of cancer harboring breast 12,13 , pancreatic 14 , colorectal 15 and lung 16 tumors, as well as fibrous histocytomas…”

Quantitative Ultrasound Molecular Imaging in Large Blood Vessel Environments

“…This method provides more accurate and quantitative measurements of adherent microbubbles, and 1.2 | Ultrasound imaging for molecular probes consumes less time than the aforementioned waiting period method [5]. In addition, it is widely implemented in pre-clinical applications including the detection of angiogenesis [32], [33], cancer [34], [35], inflammation [36]- [38], and atherosclerosis [39], [40].…”

“…Rats [31], [83], [84] and hens [85] were also used as tumor models for detection of angiogenesis. Studies showed that VEGFR2-targeted microbubbles allow for highly accurate detection of breast cancer in a murine model [34]. Additionally, microbubbles targeted to VEGFR2 and endoglin were used to monitor the therapeutic effects of gemcitabine chemotherapy in pancreatic tumors [73].…”

“…Parameters related to acoustic response of microbubbles were extracted and used to quantify the difference between specific and non-specific adhesion of microbubbles. Although quantitative assessment of disease progression has been demonstrated in small blood vessel environment [34], [51], [135], these methods relied on absolute signal magnitude, which assumes consistent attenuation and path lengths to the disease site, which is highly variable in human imaging environments. Additionally, groups have used percent contrast coverage area as a quantitative measurement [51], [135].…”

“…Pre-clinical success of ultrasound molecular imaging has been demonstrated in small blood vessel environments for various diseases including breast [31], [34], [79], prostate [155], [165] and pancreatic [71] cancers, atherosclerosis [39], [40], [137], and inflammatory diseases of the bowels [94]. In these studies, various imaging strategies have been used to address the challenge of differentiating the signal arising uniquely from bound adherent microbubbles from the signals attributable freely circulating microbubbles and tissue.…”