MR monitoring of cyclooxygenase-2 inhibition of angiogenesis in a human breast cancer model in rats

PURPOSE: To prospectively evaluate the ability of macromolecular contrast medium (MMCM)-enhanced dynamic magnetic resonance (MR) imaging to depict vascular changes in response to cyclooxygenase-2 (COX-2) inhibition of angiogenesis in a human breast cancer model. MATERIALS AND METHODS: The institutional committee for animal research approved this study. A human breast cancer cell line, MDA-MB-231, was implanted in 30 female homozygotous athymic rats that were alternately assigned to either a drug treatment group that received celecoxib on a daily basis for 7 days or a control group that received saline. Each animal underwent MR imaging after intravenous administration of a high-molecular-weight contrast agent at baseline and again 24 hours and 7 days after administration. Eleven rats in each group successfully underwent all three studies and had data sets of sufficient technical quality. A bidirectional two-compartment tissue model was used to estimate transendothelial permeability (K(PS)) and fractional plasma volume (fPV) for each tumor. Microvessel density was also measured to enable histologic assessment of angiogenesis. Repeated-measures analysis of variance and unpaired two-tailed t tests were used to evaluate differences in mean values between MR examinations performed in the same rats and between baseline values in treated and control rats, respectively. RESULTS: MR imaging-assayed microvascular K(PS) decreased significantly after 7 days of treatment with celecoxib (P < .05), but it was not significantly changed after 7 days in the control group. Likewise, microvascular density, a histologic surrogate of angiogenesis, was significantly (P < .05) lower in the treatment group than in the control group. The fPV did not significantly change in either group. CONCLUSION: Dynamic MR imaging revealed microvascular permeability to a high-molecular-weight contrast agent was significantly reduced by treatment with celecoxib.     

Dynamic MRI and tumor angiogenesis of breast cancer

The purpose of this study was to clarify the mechanism underlying early enhanced MR images of breast cancer by dynamic MR imaging from the aspect of tumor angiogenesis. The images depicted by dynamic MR imaging of breast cancer were divided into the following two groups: a marginal strong enhancement (MSE) pattern and a variable pattern without marginal strong enhancement (non-MSE). Twenty patients with invasive ductal carcinoma (maximum diameter < 2 cm) were examined by dynamic MR imaging, and the histological materials were submitted to two-dimensional computer image analysis with immunohistochemistry and histochemistry; morphological microvessel characteristics and microvessel density were examined; and the expression of vascular endothelial growth factor (VEGF) was investigated. In the MSE cases, vessel wall irregularity of capillaries and venules in the peripheral area adjacent to the tumor correlated (p < 0.001) with the enhancement pattern, and the total microvessel density (especially of arterioles with a maximum diameter less than 50 microns) of the peripheral area adjacent to the tumor was significantly higher than that of the tumor area. However, in the non-MSE cases, total microvessel density showed no significant difference between the peripheral area adjacent to the tumor and the tumor area, whereas the capillary density of the tumor area was four times greater than that of the peripheral area adjacent to the tumor. The expression of VEGF was strongly positive for the tumor nest adjacent to the capillaries. These results suggest that the enhanced images of the MSE pattern depend on abundant blood supply from arterioles and that the images of the non-MSE pattern might be reflective of angiogenic activity including variable VEGF expression of tumor cells. Thus the mechanism underlying early dynamic MR images of breast cancer was a complex result of tumor angiogenesis and the microcirculatory environment.     

Breast MRI for monitoring response of primary breast cancer to neo-adjuvant chemotherapy

The objective of the present study was to monitor response to preoperative chemotherapy with breast MRI in patients with large breast cancer. Fifty-eight women in whom core biopsy had confirmed the presence of breast carcinoma underwent breast MRI prior to beginning chemotherapy and before surgical excision. In 24 cases patients underwent one or two additional examinations during chemotherapy to monitor their progress. Breast MRI included both T2-weighted spin-echo sequences and T1-weighted gradient-echo sequences before and 1, 2, 3, and 8 min after bolus injection of gadolinium-DTPA. Tumor size and the dynamic contrast medium uptake patterns of the respective carcinomas were evaluated and compared with the final histology findings. Based on their MR tomographic findings (change in tumor size and intensity of contrast media uptake), patients were assigned to groups with non-response (NR), partial response (PR), and complete response (CR). Based on MR tomographic findings, there were 12 patients in the NR group, 34 in the PR group, and 12 in the CR group. In NR group contrast medium uptake tended to increase or show no more than minimal decrease. Diagnostic accuracy for assigning patients to the NR group was 83.3% and to the PR group 82.4%. In patients whose tumors showed only slight response to chemotherapy, breast MRI proved very reliable in determining the size of the lesions. In patients whose tumors displayed significant response and in the CR group, the size of the residual tumor was underestimated in 8 of 12 cases. In 66.7% of patients in the CR group histology revealed residual tumor masses in areas up to 5 cm in diameter. During chemotherapy, intensity of contrast medium uptake decreased in 88.2% of patients with PR and in all patients with CR. Reliable determination of response was possible within 6 weeks following the initiation of chemotherapy. Breast MRI is suitable as a monitoring method. The determination of residual tumor size is unreliable in carcinomas exhibiting significant response to chemotherapy which may lead to false-negative results. The method may be employed for monitoring response to chemotherapy after 6 weeks.     

MRI of tumor angiogenesis

Angiogenesis has long been established as a key element in the pathophysiology of tumor growth and metastasis. Increasingly, new molecularly targeted antiangiogenic drugs are being developed in the fight against cancer. These drugs bring with them a need for an accurate means of diagnosing tumor angiogenesis and monitoring response to treatment. Imaging techniques can offer this in a noninvasive way, while also providing functional information about the tumor. Among the many clinical imaging techniques available, MRI alone can provide relatively good spatial resolution and specificity, without ionizing radiation and with limited side effects. Arterial spin labeling (ASL) and blood oxygenation level-dependent (BOLD) imaging techniques can be employed to confer indirect measures of angiogenesis, such as blood flow and blood volume, without the need for external contrast agents. Dynamic contrast-enhanced (DCE)-MRI is rapidly emerging as a standard method for directly measuring angiogenesis during angiogenesis-inhibitor drug trials. As macromolecular MR contrast agents become available, they will inevitably be utilized in the assessment of tumor perfusion and vessel permeability. Meanwhile, technological advances have made imaging at a molecular level a possibility. They have brought the potential to directly target MR contrast agents to markers of angiogenesis, such as the alpha(v)beta(3) integrin. Before this is used clinically, however, substantial gains in sensitivity brought about by improved coils, pulse sequences, and contrast agents will be needed. Herein we discuss the techniques currently available for MRI of angiogenesis, along with their respective advantages and disadvantages, and what the future holds for this evolving field of imaging.     

MRI monitoring of Avastin antiangiogenesis therapy using B22956/1, a new blood pool contrast agent, in an experimental model of human cancer

PURPOSE: To evaluate the diagnostic and prognostic potential of a new protein-binding contrast medium, B22956/1, for quantitatively characterizing tumor microvessels by MRI and monitoring response to antiangiogenic therapy. MATERIALS AND METHODS: Dynamic contrast-enhanced MRI (DCE-MRI) was performed in an experimental cancer model with the use of the novel protein-binding agent B22956/1, a low molecular contrast agent (ProHance), and a macromolecular contrast medium, albumin-(Gd-DTPA). MDA-MB-435, a human cancer cell line, was implanted in 22 athymic rats. Animals were assigned randomly to a control (saline) or drug-treated (Avastin) group. MRI was performed at baseline and after nine days of treatment. The transendothelial permeability (KPS) and the fractional blood volume (fBV) were estimated from the kinetic analysis of dynamic MR data using a two-compartment model. Tumor growth was also measured from volumetric MRI. RESULTS: Tumors grew more slowly, although not significantly (P=0.07), in the drug-treated group. The KPS determined for B22956/1 decreased significantly in the drug-treated group compared to baseline (P <0.05), and progressed significantly in the control group. However, no significant changes were resolved with the use of ProHance or albumin-(Gd-DTPA). CONCLUSION: With the use of appropriate contrast media, the therapeutic effects of an anti-VEGF antibody on tumor microvessels can be monitored by dynamic MRI. The dynamic range of permeability to B22956/1, and the sensitivity to change of this parameter suggest a potential application in the clinical setting.     

Role of diffusion-weighted imaging as an adjunct to contrast-enhanced breast MRI in evaluating residual breast cancer following neoadjuvant chemotherapy

Objective

To investigate whether the addition of diffusion-weighted imaging (DWI) to dynamic contrast-enhanced MRI (DCE-MRI) improves diagnostic performance in predicting pathologic response and residual breast cancer size following neoadjuvant chemotherapy.

Materials and methods

A total of 78 consecutive patients who underwent preoperative breast MRI with DWI following neoadjuvant chemotherapy were enrolled. DWI was performed on a 1.5 T system with b values of 0 and 750 s/mm. or on a 3 T system with b values of 0 and 800 or 0 and 1000 s/mm. The images on DCE-MRI alone, DWI alone, and DCE-MRI plus DWI were retrospectively reviewed. We evaluated the diagnostic performances of the three MRI protocols for the detection of residual cancer. The tumor size as predicted by MRI was compared with histopathologic findings. Apparent diffusion coefficient (ADC) values were also compared between the groups with and without residual cancer.

Results

Of the 78 patients, 59 (75.6%) had residual cancer. For detection of residual cancer, DCE-MRI plus DWI had higher specificity (80.0%), accuracy (91.0%), and PPV (93.2%) than DCE-MRI or DWI alone (P = 0.004, P = 0.007, and P = 0.034, respectively). The ICC values for residual cancer size between MRI and histopathology were 0.891 for DCE-MRI plus DWI, 0.792 for DCE-MRI, and 0.773 for DWI. ADC values showed no significant differences between residual cancer and chemotherapeutic changes (P = 0.130).

Conclusions

The addition of DWI to DCE-MRI significantly improved diagnostic performance in predicting pathologic response and residual breast cancer size after neoadjuvant chemotherapy.     

MRI and hybrid PET/CT for monitoring tumour metastasis in a metastatic breast cancer model in rabbit

OBJECTIVE: To study tumour growth and metastasis in a rabbit metastatic breast cancer (MBC) model and find the most sensitive screening modality in monitoring tumour metastasis. METHODS: The MBC model was established by injecting a VX2 tumour mass suspension into the mammary glands of 23 rabbits and was monitored by using physical examination, X-ray, MRI and hybrid PET/CT. RESULTS: Of all 23 rabbits, axillary lymph node metastasis was detected in 21 (91%) at day 33 after tumour inoculation, mediastinal node metastasis in five (22%) at day 42, abdominal node metastasis in two (9%) at day 48, lung metastasis in six (26%) at day 39, liver metastasis in three (13%) at day 48, and lumbar spine metastasis in one (4%) at day 51. Tumour invasion of pleura was found in one, stomach wall in one, and pleura and stomach concurrently in one rabbit. Sensitivity for detection of lymph node metastases was 78.6% (22/28) and 67.9% (19/28) with MRI and PET/CT, respectively; and sensitivity for detection of metastases in distant organs was 85.7% (12/14) and 71.4% (10/14), respectively. CONCLUSIONS: The MBC model used here exhibits fast tumour growth and extensive metastasis in a relatively short period. Its metastatic pattern is quite similar to that of human MBC and hence could be potentially used as a model for testing imaging modalities and translational research, e.g., MBC management. MRI is superior to PET/CT in monitoring tumour metastasis.     

Evaluation of treatment response of cilengitide in an experimental model of breast cancer bone metastasis using dynamic PET with 18F-FDG

The purpose of this study was the assessment of the feasibility of dynamic positron emission tomography (PET) studies with fluorine-18 fluorodeoxyglucose ((18)F-FDG) to quantify effects of the cyclic Arg-Gly-Asp peptide cilengitide, which targets the ανβ 3 and ανβ 5 integrin receptors in rats with breast cancer bone metastases. Rats were inoculated with MDA-MB-231 breast cancer cells, followed by the development of lytic lesions in the hind leg. Rats with lytic lesions were treated with cilengitide five times weekly on a continuous basis from days 30 to 55 after tumor cell inoculation. Dynamic PET studies with (18)F-FDG were performed in untreated (n=9), controlled (n=4) and treated rats (n=6). The data were assessed using learning-machine two-tissue compartmental analysis. The (18)F-FDG kinetic parameters obtained by two-tissue compartmental model learning-machine showed significant differences when individual parameters were compared between the control group and treated animals. Quantitative assessment of the tracer kinetics and the application of classification analysis to the data provided us with evidence to identify those tumors that demonstrated effect of cilengitide treatment. The transport rate K1 and the phosphorylation rate k3 were significantly different (P=0.033 and 0.038, respectively). Classification analysis based on support vector machines ranking feature elimination of the combination of PET parameters revealed an overall accuracy of 80.0% between treated animals and the control group. We were able to identify 83.3% treated animals compared with the control group based on k2 and VB. In conclusion, the results revealed that cilengitide treatment of experimental breast cancer bone metastases had a significant therapeutic impact on (18)F-FDG kinetics.     

人乳腺癌肿瘤移植裸鼠模型的构建及其肿瘤浸润髓系细胞的分离

目的：人乳腺癌肿瘤移植裸鼠模型的构建及其肿瘤浸润髓系细胞的分离。方法将pHAGE-EF-ZsG-DEST质粒与病毒包装质粒pMD2．G和psPAX2首先通过磷酸钙转染方式包装带绿色荧光的慢病毒,再利用包装好的慢病毒感染BT474细胞,通过流式分选筛选阳性细胞,扩大培养后,种植于裸鼠乳腺脂肪垫,应用活体荧光成像仪和体外测量肿瘤大小,对人－裸鼠肿瘤移植模型的构建效果进行评价;通过机械法分离该小鼠模型的肿瘤浸润髓系细胞。结果筛选出带绿色荧光的BT474稳定株,种植于裸鼠乳腺脂肪垫,构建了人－裸鼠肿瘤移植模型,并分离出其肿瘤浸润髓系细胞。结论成功分离出了肿瘤浸润髓系细胞,为后续研究肿瘤浸润髓系细胞的功能奠定了基础。     

Prediction of axillary response by monitoring with ultrasound and MRI during and after neoadjuvant chemotherapy in breast cancer patients

To investigate whether monitoring with ultrasound and MR imaging before, during and after neoadjuvant chemotherapy (NAC) can predict axillary response in breast cancer patients. A total of 131 breast cancer patients with clinically positive axillary lymph node (LN) who underwent NAC and subsequent surgery were enrolled. They had ultrasound and 3.0 T-MR examinations before, during and after NAC. After reviewing ultrasound and MR images, axillary LN features and tumour size (T size) were noted. According to LN status after surgery, imaging features and their diagnostic performances were analysed. Of the 131 patients, 60 (45.8%) had positive LNs after surgery. Pre-NAC T size at ultrasound and MR was different in positive LN status after surgery (p < 0.01). There were significant differences in mid- and post-NAC number, cortical thickness (CxT), T size and T size reduction at ultrasound and mid- and post-NAC CxT, hilum, T size and T size reduction, and post-NAC ratio of diameter at MR (p < 0.03). On multivariate analysis, pre-NAC MR T size (OR, 1.03), mid-NAC ultrasound T size (OR, 1.05) and CxT (OR, 1.53), and post-NAC MR T size (OR, 1.06) and CxT (OR, 1.64) were independently associated with positive LN (p < 0.004). Combined mid-NAC ultrasound T size and CxT showed the best diagnostic performance with AUC of 0.760. Monitoring ultrasound and MR axillary LNs and T size can be useful to predict axillary response to NAC in breast cancer patients. • Monitoring morphologic features of LNs is useful to predict axillary response. • Monitoring tumour size by imaging is useful to predict axillary response. • The axillary ultrasound during NAC showed the highest diagnostic performance.     

Evaluation of tumor angiogenesis with a second-generation US contrast medium in a rat breast tumor model.

OBJECTIVE: Tumor angiogenesis is an important factor for tumor growth, treatment response and prognosis. Noninvasive imaging methods for the evaluation of tumor angiogenesis have been studied, but a method for the quantification of tumor angiogenesis has not been established. This study was designed to evaluate tumor angiogenesis in a rat breast tumor model by the use of a contrast-enhanced ultrasound (US) examination with a second-generation US contrast agent. MATERIALS AND METHODS: The alkylating agent 19N-ethyl-N-nitrosourea (ENU) was injected into the intraperitoneal cavity of 30-day-old female Sprague-Dawley rats. Three to four months later, breast tumors were detected along the mammary lines of the rats. A total of 17 breast tumors larger than 1 cm in nine rats were evaluated by gray-scale US, color Doppler US and contrast-enhanced US using SonoVue. The results were recorded as digital video images; time-intensity curves and hemodynamic parameters were analyzed. Pathological breast tumor specimens were obtained just after the US examinations. The tumor specimens were stained with hematoxylin and eosin (H & E) and the expression of CD31, an endothelial cell marker, was determined by immunohistochemical staining. We also evaluated the pathological diagnosis of the tumors and the microvessel density (MVD). Spearman's correlation and the Kruskal-Wallis test were used for the analysis. RESULTS: The pathological diagnoses were 11 invasive ductal carcinomas and six benign intraductal epithelial proliferations. The MVD did not correlate with the pathological diagnosis. However, blood volume (BV) showed a statistically significant correlation with MVD (Spearman's correlation, p < 0.05). CONCLUSION: Contrast-enhanced US using a second-generation US contrast material was useful for the evaluation of tumor angiogenesis of breast tumors in the rat.     

Diffusion‐weighted MRI for monitoring tumor response to photodynamic therapy

Purpose:

To examine diffusion‐weighted MRI (DW‐MRI) for assessing the early tumor response to photodynamic therapy (PDT).

Materials and Methods:

Subcutaneous tumor xenografts of human prostate cancer cells (CWR22) were initiated in athymic nude mice. A second‐generation photosensitizer, Pc 4, was delivered to each animal by a tail vein injection 48 h before laser illumination. A dedicated high‐field (9.4 Tesla) small animal MR scanner was used to acquire diffusion‐weighted MR images pre‐PDT and 24 h after the treatment. DW‐MRI and apparent diffusion coefficients (ADC) were analyzed for 24 treated and 5 control mice with photosensitizer only or laser light only. Tumor size, prostate specific antigen (PSA) level, and tumor histology were obtained at different time points to examine the treatment effect.

Results:

Treated mice showed significant tumor size shrinkage and decrease of PSA level within 7 days after the treatment. The average ADC of the 24 treated tumors increased 24 h after PDT (P < 0.001) comparing with pre‐PDT. The average ADC was 0.511 ± 0.119 × 10^?3 mm²/s pre‐PDT and 0.754 ± 0.181 × 10^?3 mm²/s 24 h after the PDT. There is no significant difference in ADC values pre‐PDT and 24 h after PDT in the control tumors (P = 0.20).

Conclusion:

The change of tumor ADC values measured by DW‐MRI may provide a noninvasive imaging marker for monitoring tumor response to Pc 4‐PDT as early as 24 h. J. Magn. Reson. Imaging 2010;32:409–417. © 2010 Wiley‐Liss, Inc.

     

Combined use of 18F-FDG PET/CT and MRI for response monitoring of breast cancer during neoadjuvant chemotherapy

Purpose

To explore the potential complementary value of PET/CT and dynamic contrast-enhanced MRI in predicting pathological response to neoadjuvant chemotherapy (NAC) of breast cancer and the dependency on breast cancer subtype.

Methods

We performed ¹⁸F-FDG PET/CT and MRI examinations before and during NAC. The imaging features evaluated on both examinations included baseline and changes in ¹⁸F-FDG maximum standardized uptake value (SUVmax) on PET/CT, and tumour morphology and contrast uptake kinetics on MRI. The outcome measure was a (near) pathological complete response ((near-)pCR) after surgery. Receiver operating characteristic curves with area under the curve (AUC) were used to evaluate the relationships between patient, tumour and imaging characteristics and tumour responses.

Results

Of 93 patients, 43 achieved a (near-)pCR. The responses varied among the different breast cancer subtypes. On univariate analysis the following variables were significantly associated with (near-)pCR: age (p?=?0.033), breast cancer subtype (p?<?0.001), relative change in SUVmax on PET/CT (p?<?0.001) and relative change in largest tumour diameter on MRI (p?<?0.001). The AUC for the relative reduction in SUVmax on PET/CT was 0.78 (95 % CI 0.68–0.88), and for the relative reduction in tumour diameter at late enhancement on MRI was 0.79 (95 % CI 0.70–0.89). The AUC increased to 0.90 (95 % CI 0.83–0.96) in the final multivariate model with PET/CT, MRI and breast cancer subtype combined (p?=?0.012).

Conclusion

PET/CT and MRI showed comparable value for monitoring response during NAC. Combined use of PET/CT and MRI had complementary potential. Research with more patients is required to further elucidate the dependency on breast cancer subtype.     

Sonographic monitoring of hepatic cryosurgery in an experimental animal model

Several cryosurgical techniques for freezing hepatic parenchyma have been developed. To assess the efficacy of sonographic monitoring of hepatic cryosurgery, an experimental animal model was devised. Real-time sonography was used to monitor the in vivo evolution of hypothermically induced hepatic cryolesions in four mongrel dogs. The results suggest that sonography is an effective and accurate means of monitoring the entire freezing and thawing cycle in hepatic cryosurgery.     

MR imaging in an experimental model of brain tumor immunotherapy

A murine model of implanted CNS neoplasia was used to study a new form of brain tumor immunotherapy with intralesional Corynebacterium parvum (C. parvum). Assessment of treatment protocols has been limited by the inability to assess, noninvasively, tumor burden and/or the inflammatory reaction induced in the murine brain by treatment with C. parvum. This study demonstrates that contrast-enhanced MR imaging can monitor in vivo tumor burden and the immune response to intracerebral C. parvum. KHT murine sarcoma was stereotaxically implanted into the right frontal lobe of C3H/HeN mice at doses of 10,000 and 50,000 tumor cells. The KHT sarcoma is 100% fatal in untreated mice. Therapy consisted of an intraperitoneal injection of 350 micrograms of killed C. parvum 1 day after tumor implantation followed by 70 micrograms of C. parvum stereotaxically injected into the tumor 5 days after implantation. MR imaging was performed on mice injected with saline only, C parvum only, tumor only, and tumor treated with C. parvum. C. parvum alone elicited an intense transitory mononuclear cell inflammatory reaction in the meninges, ependyma, and to a variable degree at the injection site. The inflammatory response reached a peak 2 weeks after intracerebral injection. Contrast-enhanced MR imaging was able to detect the presence and severity of C. parvum-induced inflammation, which decreased 3 weeks after intracerebral injection. The transitory nature of this type of inflammation should allow its differentiation from tumor in subjects undergoing serial scanning following intracerebral injection of C. parvum as a form of brain tumor immunotherapy.