Evaluation of novel combined carbogen USPIO (CUSPIO) imaging biomarkers in assessing the antiangiogenic effects of cediranib (AZD2171) in rat C6 gliomas

Clinical Activity and Safety of Cediranib and Olaparib Combination in Patients with Metastatic Pancreatic Ductal Adenocarcinoma without BRCA Mutation

Lessons Learned

Cediranib and olaparib combination did not result in clinically meaningful activity in patients with metastatic pancreatic ductal adenocarcinoma without known BRCA mutation.

Background

Cediranib, a vascular endothelial growth factor receptor inhibitor, suppresses expression of BRCA1/2 and RAD51 inducing homologous recombination DNA repair deficiency (HRD) in several cancer cell lines and xenograft models [1]. Olaparib provides a clinical benefit in patients with metastatic pancreatic adenocarcinoma (mPDAC) with germline BRCA mutation (gBRCAmt) [2]. We hypothesized that cediranib induces HRD in the absence of gBRCAmt and synergizes with olaparib, resulting in an objective response in patients with mPDAC.

Methods

Patients with mPDAC with at least one prior systemic chemotherapy were enrolled. Patients with known gBRCAmt were excluded. Patients took cediranib 30 mg daily and olaparib 200 mg twice daily, orally. The primary endpoint was objective response (OR) rate.

Results

Nineteen patients received the study drugs. Seven patients came off treatment before the first restaging scan: six because of clinical progression and one because of an adverse event. No OR was observed. Six patients had stable disease (SD) as a best overall response. The median duration of SD was 3.1 months. The median overall survival was 3.4 months. Common treatment‐related adverse events were fatigue, hypertension, and diarrhea.

Conclusion

Cediranib and olaparib combination did not result in clinically meaningful activity in patients with mPDAC without gBRCAmt.

Monitoring the Vascular Response and Resistance to Sunitinib in Renal Cell Carcinoma In Vivo with Susceptibility Contrast MRI

Antiangiogenic therapy is efficacious in metastatic renal cell carcinoma (mRCC). However, the ability of antiangiogenic drugs to delay tumor progression and extend survival is limited, due to either innate or acquired drug resistance. Furthermore, there are currently no validated biomarkers that predict which mRCC patients will benefit from antiangiogenic therapy. Here, we exploit susceptibility contrast MRI (SC-MRI) using intravascular ultrasmall superparamagnetic iron oxide particles to quantify and evaluate tumor fractional blood volume (fBV) as a noninvasive imaging biomarker of response to the antiangiogenic drug sunitinib. We also interrogate the vascular phenotype of RCC xenografts exhibiting acquired resistance to sunitinib. SC-MRI of 786-0 xenografts prior to and 2 weeks after daily treatment with 40 mg/kg sunitinib revealed a 71% (P < 0.01) reduction in fBV in the absence of any change in tumor volume. This response was associated with significantly lower microvessel density (P < 0.01) and lower uptake of the perfusion marker Hoechst 33342 (P < 0.05). The average pretreatment tumor fBV was negatively correlated (R2 = 0.92, P < 0.0001) with sunitinib-induced changes in tumor fBV across the cohort. SC-MRI also revealed suppressed fBV in tumors that acquired resistance to sunitinib. In conclusion, SC-MRI enabled monitoring of the antiangiogenic response of 786-0 RCC xenografts to sunitinib, which revealed that pretreatment tumor fBV was found to be a predictive biomarker of subsequent reduction in tumor blood volume in response to sunitinib, and acquired resistance to sunitinib was not associated with a parallel increase in tumor blood volume. Cancer Res; 77(15); 4127-34. ©2017 AACR.

Investigating the Vascular Phenotype of Subcutaneously and Orthotopically Propagated PC3 Prostate Cancer Xenografts Using Combined Carbogen Ultrasmall Superparamagnetic Iron Oxide MRI

The aim of this study was to use the combined carbogen-ultrasmall superparamagnetic iron oxide (CUSPIO) magnetic resonance imaging (MRI) method, which uses spatial correlations in independent susceptibility imaging biomarkers, to investigate and compare the impact of tumor size and anatomical site on vascular structure and function in vivo. Mice bearing either subcutaneous or orthotopic PC3 LN3 prostate tumors were imaged at 7 T, using a multi-gradient echo sequence to quantify R2, before and during carbogen (95% O2/5% CO2) breathing, and subsequently following intravenous administration of USPIO particles. Carbogen and USPIO-induced changes in R2 were used to inform on hemodynamic vasculature and fractional blood volume (%), respectively. The CUSPIO imaging data were also segmented to identify and assess five categories of R2 response. Small and large subcutaneous and orthotopic tumor cohorts all exhibited significantly (P < 0.05) different median baseline R2, ΔR2carbogen, and fractional blood volume. CUSPIO imaging showed that small subcutaneous tumors predominantly exhibited a negative ΔR2carbogen followed by a positive ΔR2USPIO, consistent with a well perfused tumor vasculature. Large subcutaneous tumors exhibited a small positive ΔR2carbogen and relatively low fractional blood volume, suggesting less functional vasculature. Orthotopic tumors revealed a large, positive ΔR2carbogen, consistent with vascular steal, and which may indicate that vascular function is more dependent on site of implantation than tumor size. Regions exhibiting significant ΔR2carbogen, but no significant ΔR2USPIO, suggesting transient vascular shutdown over the experimental timecourse, were apparent in all 3 cohorts. CUSPIO imaging can inform on efficient drug delivery via functional vasculature in vivo, and on appropriate tumor model selection for pre-clinical therapy trials.

Investigating the role of tumour cell derived iNOS on tumour growth and vasculature in vivo using a tetracycline regulated expression system

Nitric oxide (NO) is a free radical signalling molecule involved in various physiological and pathological processes, including cancer. Both tumouricidal and tumour promoting effects have been attributed to NO, making its role in cancer biology controversial and unclear. To investigate the specific role of tumour-derived NO in vascular development, C6 glioma cells were genetically modified to include a doxycycline regulated gene expression system that controls the expression of an antisense RNA to inducible nitric oxide synthase (iNOS) to manipulate endogenous iNOS expression. Xenografts of these cells were propagated in the presence or absence of doxycycline. Susceptibility magnetic resonance imaging (MRI), initially with a carbogen (95% O2/5% CO2) breathing challenge and subsequently an intravascular blood pool contrast agent, was used to assess haemodynamic vasculature (ΔR2*) and fractional blood volume (fBV), and correlated with histopathological assessment of tumour vascular density, maturation and function. Inhibition of NO production in C6 gliomas led to significant growth delay and inhibition of vessel maturation. Parametric fBV maps were used to identify vascularised regions from which the carbogen-induced ΔR2* was measured and found to be positively correlated with vessel maturation, quantified ex vivo using fluorescence microscopy for endothelial and perivascular cell staining. These data suggest that tumour-derived iNOS is an important mediator of tumour growth and vessel maturation, hence a promising target for anti-vascular cancer therapies. The combination of ΔR2* response to carbogen and fBV MRI can provide a marker of tumour vessel maturation that could be applied to non-invasively monitor treatment response to iNOS inhibitors.

Clinical applications of iron oxide nanoparticles for magnetic resonance imaging of brain tumors

Current neuroimaging provides detailed anatomic and functional evaluation of brain tumors, allowing for improved diagnostic and prognostic capabilities. Some challenges persist even with today's advanced imaging techniques, including accurate delineation of tumor margins and distinguishing treatment effects from residual or recurrent tumor. Ultrasmall superparamagnetic iron oxide nanoparticles are an emerging tool that can add clinically useful information due to their distinct physiochemical features and biodistribution, while having a good safety profile. Nanoparticles can be used as a platform for theranostic drugs, which have shown great promise for the treatment of CNS malignancies. This review will provide an overview of clinical ultrasmall superparamagnetic iron oxides and how they can be applied to the diagnostic and therapeutic neuro-oncologic setting.

CT perfusion imaging as an early biomarker of differential response to stereotactic radiosurgery in C6 rat gliomas

BACKGROUND

The therapeutic efficacy of stereotactic radiosurgery for glioblastoma is not well understood, and there needs to be an effective biomarker to identify patients who might benefit from this treatment. This study investigated the efficacy of computed tomography (CT) perfusion imaging as an early imaging biomarker of response to stereotactic radiosurgery in a malignant rat glioma model.

METHODS

Rats with orthotopic C6 glioma tumors received either mock irradiation (controls, N = 8) or stereotactic radiosurgery (N = 25, 12 Gy in one fraction) delivered by Helical Tomotherapy. Twelve irradiated animals were sacrificed four days after stereotactic radiosurgery to assess acute CT perfusion and histological changes, and 13 irradiated animals were used to study survival. Irradiated animals with survival >15 days were designated as responders while those with survival ≤15 days were non-responders. Longitudinal CT perfusion imaging was performed at baseline and regularly for eight weeks post-baseline.

RESULTS

Early signs of radiation-induced injury were observed on histology. There was an overall survival benefit following stereotactic radiosurgery when compared to the controls (log-rank P<0.04). Responders to stereotactic radiosurgery showed lower relative blood volume (rBV), and permeability-surface area (PS) product on day 7 post-stereotactic radiosurgery when compared to controls and non-responders (P<0.05). rBV and PS on day 7 showed correlations with overall survival (P<0.05), and were predictive of survival with 92% accuracy.

CONCLUSIONS

Response to stereotactic radiosurgery was heterogeneous, and early selection of responders and non-responders was possible using CT perfusion imaging. Validation of CT perfusion indices for response assessment is necessary before clinical implementation.

Exploring ΔR(2) * and ΔR(1) as imaging biomarkers of tumor oxygenation

PURPOSE

To investigate the combined use of hyperoxia-inducedΔR(2) * and ΔR(1) as a noninvasive imaging biomarker of tumor hypoxia.

MATERIALS AND METHODS

MRI was performed on rat GH3 prolactinomas (n = 6) and human PC3 prostate xenografts (n = 6) propagated in nude mice. multiple gradient echo and inversion recovery truefisp images were acquired from identical transverse slices to quantify tumor R(2) * and R(1)before and during carbogen (95% O2 /5% CO2 ) challenge, and correlates of ΔR(2) * and ΔR(1) assessed.

RESULTS

Mean baseline R(2) * and R(1) were 119 ± 7 s(-1) and 0.6 ± 0.03 s(-1) for GH3 prolactinomas and 77 ± 12 s(-1) and 0.7 ± 0.02 s(-1) for PC3 xenografts, respectively. During carbogen breathing, mean ΔR(2) * and ΔR(1) were -20 ± 8 s(-1) and 0.08 ± 0.03 s(-1) for GH3 and -0.5 ± 1 s(-1) and 0.2 ± 0.08 s(-1) for the PC3 tumors, respectively. A pronounced relationship betweenΔR(2) * and ΔR(1) was revealed.

CONCLUSION

Considering the blood oxygen-hemoglobin dissociation curve, fast R2 * suggested that GH3 prolactinomas were more hypoxic at baseline, and their carbogen response dominated by increased hemoglobin oxygenation, evidenced by highly negative ΔR(2) *. PC3 tumors were less hypoxic at baseline, and their response to carbogen dominated by increased dissolved oxygen, evidenced by highly positive ΔR(1) . Because the two biomarkers are sensitive to different oxygenation ranges, the combination of ΔR(2) * and ΔR(1) may better characterize tumor hypoxia than each alone.

Clinical applications of susceptibility-weighted imaging in detecting and grading intracranial gliomas: a review

Susceptibility-weighted imaging (SWI) is a technique that exploits the susceptibility difference between tissues to provide contrast for different regions of the brain. In essence, it uses the deoxygenated hemoglobin of veins, hemosiderin of hemorrhage, etc. as intrinsic contrast agents, allowing for much better visualization of blood and microvessels even without administration of an external contrast agent. It is a fast-evolving field that is being constantly improved and increasingly implemented with updates in relevant technology. Multiple studies have been done on the role of SWI in the management of various neurologic disorders and it is also being seen as a further step in the neuroradiologist’s goal of being able to noninvasively grade tumors in order to influence therapy. This article briefly reviews the evolution of SWI since its conception and provides the reader with a comprehensive summary of various studies that have been done on its application for detecting and grading intraaxial brain tumors, specifically gliomas. Other useful magnetic resonance techniques that have shown promise in grading gliomas are also discussed.

Evaluation of clinically translatable MR imaging biomarkers of therapeutic response in the TH-MYCN transgenic mouse model of neuroblastoma

PURPOSE

To evaluate noninvasive and clinically translatable magnetic resonance (MR) imaging biomarkers of therapeutic response in the TH-MYCN transgenic mouse model of aggressive, MYCN-amplified neuroblastoma.

MATERIALS AND METHODS

All experiments were performed in accordance with the local ethical review panel and the UK Home Office Animals Scientific Procedures Act 1986 and with the UK National Cancer Research Institute guidelines for the welfare of animals in cancer research. Multiparametric MR imaging was performed of abdominal tumors found in the TH-MYCN model. T2-weighted MR imaging, quantitation of native relaxation times T1 and T2, the relaxation rate R2*, and dynamic contrast-enhanced MR imaging were used to monitor tumor response to cyclophosphamide (25 mg/kg), the vascular disrupting agent ZD6126 (200 mg/kg), or the antiangiogenic agent cediranib (6 mg/kg, daily). Any significant changes in the measured parameters, and in the magnitude of the changes after treatment between treated and control cohorts, were identified by using Student two-tailed paired and unpaired t test, respectively, with a 5% level of significance.

RESULTS

Treatment with cyclophosphamide or cediranib induced a 54% or 20% reduction in tumor volume at 48 hours, respectively (P < .005 and P < .005, respectively; P < .005 and P < .005 versus control, respectively). Treatment with ZD6126 induced a 45% reduction in mean tumor volume 24 hours after treatment (P < .005; P < .005 versus control). The antitumor activity of cyclophosphamide, cediranib, and ZD6126 was consistently associated with a decrease in tumor T1 (P < .005, P < .005, and P < .005, respectively; P < .005, P < .005, and P < .005 versus control, respectively) and with a correlation between therapy-induced changes in native T1 and changes in tumor volume (r = 0.56; P < .005). Tumor response to cediranib was also associated with a decrease in the dynamic contrast-enhanced MR imaging-derived volume transfer constant (P = .07; P < .05 versus control) and enhancing fraction (P < .05; P < .01 versus control), and an increase in R2* (P < .005; P < .05 versus control).

CONCLUSION

The T1 relaxation time is a robust noninvasive imaging biomarker of response to therapy in tumors in TH-MYCN mice, which emulate high-risk neuroblastoma in children. T1 measurements can be readily implemented on clinical MR systems and should be investigated in translational clinical trials of new targeted therapies for pediatric neuroblastoma.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.12120128/-/DC1.