Table 4.

Examples of non-invasive imaging studies assessing anti-angiogenic therapy effects

Imaging Modality	Contrast Agent	Determined Parameter	Antiangiogenic Agent	Mechanism of Action	Setting	Assessed Effects in the Therapy vs. Control Group	Ref.
DCE-μCT	Ultravist 300 (500 mg iodine/kg bolus in 2 s)	total tumor volume [cm3] rBV [%] vascular permeability K [μl min−1 ml−1] AUC [HU]	everolimus (10 mg, thrice per week)	mTOR inhibitor	MCF7 mammary cancer xenografts	total tumor volume ↓ P = 0.001 rBV ↓ P = 0.029 - 0.136 * K ↓ P = 0.032 - 0.243 * AUC↓ P = 0.007 - 0.023 * * Depending on the segmented region of the tumor (total vs. peripheral vs. central). Most significant differences were observed in the tumor periphery.	[20]
DCE-μCT	Omnipaque 300 (2.2 μl/g)	total tumor volume [cm3] BF [ml/min per 100 g] BV [ml/100 g] MTT [s] PS (permeability surface area product) [ml/min per 100 g]	vanetinib (50 mg/kg, 2 applications in 24 hours)	multi-targeted receptor tyrosine kinase inhibitor	LoVo colon adenocarcinoma xenografts	Nonhypovascular tumors: total tumor volume ↓ P > 0.05 BF ↓ P < 0.05 BV ↓ P < 0.05 MTT↓ P > 0.05 PS ↑ P > 0.05 Hypovascular tumors showed no significant differences	[21]
Ex vivo high- resolution μCT	Microfil	MVD [%] relative vessel volume vascular branching by tree analysis	bevacizumab (5 mg/ 200 μl over 24 h continuously per pump for 14 d)	humanized monoclonal anti-VEGF-A antibody	A549 orthotopic lung adenocarcinomic xenografts	MVD ↓ P < 0.0001 relative vessel volume ↓ P <0.05 substantially less branching points at smaller vessel diameters (<25 mm2)	[25]
DCE-MRI	Magnevist (0.4 mmol/kg Gd- DTPA bolus in 5s)	Kep (exchange rate constant) based on the pharmacokinetic two-compartment model of Brix amplitude A (increase of signal intensity relative to precontrast value	DC101 (800 μg i.p. thrice a week)	VEGFR-2 antibody	HaCaT-ras-A-5RT3 skin squamous cell carcinoma xenografts	A ↓ rapidly during initial phase of anti-angiogenic therapy (4 days) differences in tumor volumes were not significant during the initial phase later, when treated tumors had decreased in volume while non-treated tumors had continuously increased their volumes, A re-increased in treated tumors no significant differences for Kep for the whole examination period	[36]
VSI MRI	very small superparamagnetic iron oxid nanoparticles (200 μmol Fe/kg)	vessel size index (VSI)	sunitinib for A431 (60mg/kg i.p.) bevacizumab for HaCaT-ras- A-5RT3 (1mg i.p. twice a week)	multi-targeted receptor tyrosine kinase inhibitor & humanized monoclonal anti-VEGF-A antibody	A431 epidermoid carcinoma xenografts HaCaT-ras-A-5RT3 skin squamous cell carcinoma xenografts	VSI ↑ in sunitinib treated A431 tumors (P < 0.05) no significant changes in VSI in bevacizumab treated HaCaT-ras- A-5RT3 tumors	[43]
Bold MRI	generated contrast by photo- consumption of oxygen and hemodynamic effects resulting from PDT application	T2-weighted MRSI (magnetic resonance signal intensity) [% of baseline at t0] ΔR2* (defined as R2* illumination minus R2* pre illumination) [1/s]	simultaneous TOOKAD (5 mg/kg) and transcutaneous PDT	TOOKAD: photo- sensitizing, vascular disrupting agent	M2R melanoma xenografts	MRSI ↓ rapid increase of ΔR2* in treated tumors rapid decrease of ΔR2* in untreated tumors	[46]
Volumetric Power Doppler Ultrasound	bolus injection of 100 μl of MB	tumor volume color pixel density	sunitinib (80 mg/kg daily i.p.)	multi-targeted receptor tyrosine kinase inhibitor	A431 epidermoid carcinoma xenografts	tumor volume ↓ over time (P < 0.05 at day 3 and P < 0.01 at day 6) in contrast-enhanced scans color pixel density rapidly↓ (P < 0.01 at day 3) in non-contrast-enhanced scans color pixel density slowly↓, but then reincreases indicating that different vessel fractions were captured with each of this methods (see figure 2B)	[64]
Power Doppler Ultrasound	bolus injection of 100 μl of galactose-based US contrast agent (300 mg/ml Levovist)	blood volume blood flow perfusion (i.e. blood flow normalized to tissue volume) mean blood velocity	DC101 (800 μg i.p. thrice a week)	VEGFR-2 antibody	HaCaT-ras-A-5RT3 skin squamous cell carcinoma xenografts	reduction in tumor vasculature was assessable before a reduction in tumor size became visible blood volume ↓ in treated and ↑ in untreated animals blood flow ↓ P < 0.05 mean blood velocity ↓ but no significance central tumor perfusion ↓ in treated and ↑ in untreated animals	[65]
Power Doppler Ultrasound	αvβ3-specific MB ICAM-1-specific MB (injection of 300 μl of a 108 MB/ml suspension)	color pixel density	16-Gy single dose of 12C	DNA damage	AT-1 prostate cancer xenografts	color pixel density ↑by using αvβ3-specific MB in irradiated tumors after 3 days (P < 0.05) color pixel density for ICAM-1-specific MB showed no significant changes	[69]
OI - FMT	Annexin Vivo 750 (2 nmol 2 h prior imaging) AngioSense 680 (2 nmol 2 h immediately before imaging)	Annexin Vivo accumulation (specific for apoptotic cells) AngioSense accumulation (blood pool marker)	sunitinib (50 mg/kg daily i.p.)	multi-targeted receptor tyrosine kinase inhibitor	A431 epidermoid carcinoma xenografts	Annexin Vivo accumulation ↓ P = 0.13 (contradictory to high apoptotic rates proven by TUNEL staining) AngioSense accumulation ↓ P = 0.51 (in tendency in line with CD31 area fraction, P < 0.001)	[76]
PET	18F-FDG 18F-FLT 18F-FPPRGD2 (1.85 MBq per mouse)	glucose metabolism specific 18F-FDG uptake proliferation specific 18F-FLT uptake αvβ3 integrin-specific 18F-FPPRGD2 Uptake	ZD4190 (100 mg/kg orally per day for three days)	VEGFR-2 tyrosine kinase inhibitor	MDA-MB-435 orthotopic breast carcinoma xenografts	no significant changes in 18F-FDG uptake 18F-FLT uptake ↓ during initial phase of anti- angiogenic therapy (at day 3, P < 0.001) 18F-FPPRGD2 uptake ↓ during initial phase of anti- angiogenic therapy (at day 3, P < 0.001), then re-increase back to baseline	[93]
PET	18F-FLT (2.0 MBq/kg)	proliferation specific 18F-FLT SUV (standardized uptake value)	bevacizumab & irinotecan	humanized monoclonal anti-VEGF-A antibody & topoisomerase I inhibitor	30 Glioma patients	18F-FLT tumor uptake ↓ in responder (46±14 %) vs. 18F-FLT uptake ↑ in non-responder (20±52 %); P = 0.001 18F-FLT tumor uptake changes at 2 and 6 weeks were significant predictors of progression-free and overall survival by Kaplan-Meier analysis (P < 0.001); sensitivity: 82%; specificity: 80%	[96]