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Background: The aim of the present study was to compare the biological effectiveness of carbon ions relative to x-rays between tumor control, acute skin reaction and late RIF of CDF1 mice., Material and Methods: CDF1 mice with a C3H mouse mammary carcinoma implanted subcutaneously on the foot of the right hind limb were irradiated with single fractions of either photons, or (12)C ions using a 30-mm spread-out Bragg peak. The endpoint of the study was local control (no tumor recurrence within 90 days). For the acute skin reaction, non-tumor bearing CDF1 mice were irradiated with a comparable radiation scheme, and monitored for acute skin damage between Day 7 and 40. Late RIF was assessed in the irradiated mice., Results: The TCD50 (dose producing tumor control in 50% of mice) values with 95% confidence interval were 29.7 (25.4-34.8) Gy for C ions and 43.9 (39.2-49.2) Gy for photons, with a corresponding Relative biological effectiveness (RBE) value of 1.48 (1.28-1.72). For acute skin damage the MDD50 (dose to produce moist desquamation in 50% of mice) values with 95% confidence interval were 26.3 (23.0-30.1) Gy for C ions and 35.8 (32.9-39.0) Gy for photons, resulting in a RBE of 1.36 (1.20-1.54). For late radiation-induced fibrosis the FD50 (dose to produce severe fibrosis in 50% of mice) values with 95% confidence interval were 26.5 (23.1-30.3) Gy for carbon ions and 39.8 (37.8-41.8) Gy for photons, with a RBE of 1.50 (1.33-1.69)., Conclusion: The observed RBE values were very similar for tumor response, acute skin damage and late RIF when irradiated with large doses of high- linear energy transfer (LET) carbon ions. This study adds information to the variation in biological effectiveness in different tumor and normal tissue models.

Background: Hypoxia is a characteristic feature of solid tumours that significantly reduces the efficacy of conventional radiation therapy. In this study we investigated the role of hypoxia in a stereotactic radiation schedule by using a variety of hypoxic modifiers in a preclinical tumour model., Material and Methods: C3H mammary carcinomas were irradiated with 3 × 15 Gy during a one-week period, followed three days later by a clamped top-up dose to produce a dose response curve; the endpoint was tumour control. The hypoxic modifiers were nimorazole (200 mg/kg), nicotinamide (120 mg/kg) and carbogen (95% O2 + 5% CO2) breathing, OXi4503 (10 mg/kg), and hyperthermia (41.5°C; 1 h)., Results: The radiation dose controlling 50% of clamped tumours (TCD50) following 3 × 15 Gy was 30 Gy. Giving nimorazole or nicotinamide+ carbogen prior to the final 15 Gy fraction non-significantly (χ(2)-test; p < 0.05) reduced this TCD50 to 20-23 Gy; when administered with each 3 × 15 Gy fraction these values were significantly reduced to ≤ 2.5 Gy. Injecting OXi4503 or heating after irradiating significantly reduced the TCD50 to 9-12 Gy regardless of whether administered with one or all three 15 Gy fractions. Combining OXi4503 and heat with the final 15 Gy had a significantly larger effect (TCD50 = 2 Gy)., Conclusions: Clinically relevant modifiers of hypoxia effectively enhanced an equivalent stereotactic radiation treatment confirming the importance of hypoxia in such schedules.

Introduction: Hypoxic tumor cells are radioresistant, therefore, identification of hypoxia is crucial. Hyperpolarized magnetic resonance spectroscopy (HPMRS) allows real time measurements of the conversion of pyruvate to lactate, the final step of anaerobic energy production, and may thus allow non-invasive identification of hypoxia or treatment-induced changes in oxygenation. The aim of the study was to investigate the usefulness of HPMRS as a means to assess tumor hypoxia and its dynamics during intervention., Material and Methods: C3H mammary carcinomas grown in CDF1 mice were used. To manipulate with tumor oxygenation, non-anaesthetized mice were gassed with air, 10% or 100% oxygen prior to administration of hyperpolarized [1-¹³C]pyruvate and HPMRS analysis. A direct assessment of tumor oxygen partial pressure (pO2) distributions were made using the Eppendorf oxygen electrode in a separate, but similarly treated, group of mice., Results: Even though breathing 100% oxygen improved tumor oxygenation as evidenced by pO2 measurements, the mean (with 1 S.E.) [1-¹³C]lactate/[1-¹³C]pyruvate ratio was unaffected by this intervention, being 34 (30-37) in mice breathing air and 37 (33-42) in mice breathing 100% oxygen. In contrast, and in accordance with pO2 measurements, a significant increase in the [1-¹³C]lactate/[1-¹³C]pyruvate ratio was seen in 10% oxygen-breathing mice with a ratio of 46 (42-50)., Conclusions: Although, no metabolic change was observed during 100% O2 breathing using HPMRS, the significant increase in the [1-¹³C]lactate/[1-¹³C]pyruvate ratio during 10% oxygen breathing suggests, that HPMRS can detect hypoxia-driven changes in the metabolic fate of pyruvate. To what extent and for what purposes HPMRS may best supplement or complement established techniques like hypoxia PET needs to be unraveled in future research.

Purpose: This pre-clinical study was designed to investigate the effect of various vascular disrupting agents (VDAs) that have undergone or are in clinical evaluation, had on the oxygenation status of tumours and what effects that could have on the combination with radiation., Material and Methods: The tumour model was a C3H mammary carcinoma grown in the right rear foot of female CDF1 mice and treated when at 200 mm(3) in size. The VDAs were the flavenoid compounds flavone acetic acid (FAA) and its more recent derivative 5,6-dimethylxanthenone-4-acetic acid (DMXAA), and the leading tubulin binding agent combretastatin A-4 phosphate (CA4P) and the A-1 analogue OXi4503. Oxygenation status was estimated using the Eppendorf oxygen electrode three hours after drug injection. Radiation response was determined following single or fractionated (10 fractions in 12 days) irradiations with a 240 kV x-ray machine using either a tumour re-growth or local tumour control assay., Results: All VDAs significantly reduced the oxygenation status of the tumours. They also influenced radiation response, but the affect was time and sequence dependent using single radiation schedules; an enhanced effect when the VDAs were injected at the same time or after irradiating, but no or even a reduced effect when given prior to irradiation. Only OXi4503 showed an increased response when given before the radiation. CA4P and OXi4503 also enhanced a fractionated radiation treatment if the drugs were administered after fractions 5 and 10., Conclusions: VDAs clearly induced tumour hypoxia. This had the potential to decrease the efficacy of radiation. However, if the appropriate timing and scheduling were used an enhanced effect was observed using both single and fractionated radiation treatments.

Kinetic analysis of the mode of inhibition of cathepsin L by KGP94, a lead compound from a privileged library of functionalized benzophenone thiosemicarbazone derivatives, demonstrated that it is a time-dependent, reversible, and competitive inhibitor of the enzyme. These results are consistent with the formation of a transient covalent bond, and are supported by molecular modeling that places the thiocarbonyl of the inhibitor in proximity to the thiolate moiety of the enzyme active site Cys25. KGP94 significantly decreased the activity of cathepsin L toward human type I collagen, and impeded both migration and invasion of MDA-MB-231 human breast cancer cells. Growth retardation was achieved in vivo against both recently implanted and established tumours using a C3H mouse mammary carcinoma model., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Purpose: This study investigated the anti-tumour effects of the novel vascular disrupting agent plinabulin (NPI-2358) when given alone or combined with radiation., Materials and Methods: Foot implanted C3H mammary carcinomas or leg implanted KHT sarcomas were used, with plinabulin injected intraperitoneally. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) measurements were made with gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) on a 7-tesla magnet. Treatment response was assessed using regrowth delay (C3H tumours), clonogenic survival (KHT sarcomas) or histological estimates of necrosis for both models., Results: Plinabulin (7.5 mg/kg) significantly reduced the initial area under curve (IAUC) and the transfer constant (K(trans)) within 1 hour after injection, reaching a nadir at 3 h, but returning to normal within 24 h. A dose-dependent decrease in IAUC and K(trans), was seen at 3 h. No significant anti-tumour effects were observed in the C3H tumours until doses of 12.5 mg/kg were achieved, but started at 1.5 mg/kg in the KHT sarcoma. Irradiating tumours 1 h after injecting plinabulin enhanced response in both models., Conclusions: Plinabulin induced a time- and dose-dependent decrease in tumour perfusion. The KHT sarcoma was more sensitive than the C3H tumour to the anti-tumour effects of plinabulin, while radiation response was enhanced in both models.

Purpose: Tumor hypoxia is a known cause of resistance to radiotherapy. The aim of this study was to investigate the prognostic value of hypoxia measured by (18)F-fluoroazomycin arabinoside ((18)F-FAZA) PET or the Eppendorf oxygen electrode in a pre-clinical tumor model., Material/methods: Pretreatment (18)F-FAZA PET scans and blood sampling was conducted in 92 Female CDF1 mice with subcutaneous C3H mammary carcinomas grown in the right foot. Similarly, oxygenation status of 80 equivalent tumors was assessed using an invasive oxygen sensitive electrode. Tumors were then irradiated with a single dose of 55 Gy and local tumor control up to 90 days after the treatment was determined., Results: A significant difference in local tumor control between "more hypoxic" or "less hypoxic" groups separated either by a median (18)F-FAZA PET determined tumor-to-blood ratio (P=0.007; hazard ratio, HR=0.21 [95% CI: 0.06-0.74]), or the fraction of oxygen partial pressure (pO(2)) values ≤2.5 mmHg (P=0.018; HR=0.31 [95% CI: 0.11-0.87]), was found. Both assays showed that the more hypoxic tumors had significantly lower tumor control., Conclusion: (18)F-FAZA PET analysis showed that pre treatment tumor hypoxia was prognostic of radiation response. Similar results were obtained when oxygenation status was assessed by the Eppendorf pO(2) Histograph. The results of this study support the role of (18)F-FAZA as a non-invasive prognostic marker for tumor hypoxia., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Purpose: Combretastatin A-4 phosphate (CA4P) is a promising vascular disrupting agent in cancer treatment, but elicits hypertension in patients. The aim of this study was to use a mouse model to investigate whether hypertension or its modification influenced the treatment efficacy of CA4P in combination with other therapies., Material and Methods: C3H mammary carcinoma bearing or non-bearing CDF1 mice were used. The effects of CA4P alone or in combination with the antihypertensive drug hydralazine (HDZ) on mean arterial blood pressure (MABP), hematocrit (Hct) and hemoglobin concentration ([Hb]) were characterized in non-tumor-bearing animals. Tumor-bearing mice were also treated locally with radiation and/or hyperthermia (41.5 ° C; 60 min) in combination with CA4P alone or CA4P plus HDZ, and TCD50 values (radiation dose that controls 50% of tumors) determined., Results: Hct, [Hb] and MABP respectively increased from 49.3 ± 0.3%, 9.1 ± 0.1mM and 110 ± 7 mm Hg, to 54.7 ± 0.2%, 10.3 ± 0.1 mM and 127 ± 5 mm Hg, within 1h after injecting 100 mg/kg CA4P. For each parameter the magnitude of the peak increase was largely dose independent within the CA4P dose range tested (10-250 mg/kg). However, high CA4P doses delayed the return to baseline and Hct and [Hb] recovered more slowly than MABP. Co-administration of HDZ (0.2mg/kg) was able to suppress the CA4P-induced increase in MABP for several hours but did not noticeably affect the changes in Hct and [Hb]. The TCD50 value (± 95% confidence interval) for radiation alone was 53 (51-55) Gy. Tumor irradiation followed by injection of either CA4P (100 mg/kg) or CA4P+HDZ 30 min later reduced the TCD50 values to 50 (46-54) Gy and 48 (45-52) Gy, respectively. Heating tumors after irradiating further decreased the TCD50 value to 46 (43-48) Gy. When all treatments were combined the TCD50 was 35 (32-38) Gy, regardless of whether the drugs were CA4P or CA4P+HDZ., Conclusions: CA4P significantly increased Hct, [Hb] and MABP. Hypertension, but not increases in Hct and [Hb], could be reversed with the antihypertensive drug HDZ. CA4P significantly improved tumor response to radiation or thermoradiation, neither of which was influenced by the addition of HDZ., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Introduction: The efficacy of the vascular disrupting agent combretastatin A-4 phosphate (CA4P) depends on several factors including tumor size, nitric oxide level, interstitial fluid pressure, and vascular permeability. These factors vary among tumor types. The aim of this study was to investigate all these factors in two tumor models that respond differently to CA4P., Material and Methods: Mice bearing C3H mammary carcinomas or KHT sarcomas (200 to 800 mm(3)) were intraperitoneally injected with CA4P (100 mg/kg). Tumor size and the effect of a nitric oxide inhibitor nitro-L-arginine (NLA) administered intravenously were evaluated by necrotic fraction histologically assessed at 24 hours. Interstitial fluid pressure (IFP) was measured using the wick-in-needle technique, and vascular characteristics were assessed with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI)., Results: Initial necrotic fraction was about 10% in both tumor models at 200 mm(3), but only increased significantly with tumor size in the C3H mammary carcinoma. In this tumor, CA4P significantly induced further necrosis by about 15% at all sizes, but in the KHT tumor, the induced necrotic fraction depended on tumor size. For both tumor types, NLA with CA4P significantly increased necrotic fraction above that for each drug alone. CA4P significantly decreased IFP in all tumors except in the 800 mm(3) C3H tumor, which had an initially non-significant lower value. Interstitial volume estimated by DCE-MRI increased in all groups, except the 800 mm(3) C3H tumors. DCE-MRI vascular parameters showed different initial characteristics and general significant reductions following CA4P treatment., Conclusions: Both tumor models showed differences in all factors before treatment, and in their response to CA4P. Perfusion and permeability as estimated by DCE-MRI play a central role in the CA4P response, and interstitial volume and IFP seemed related. These factors may be of clinical value in the planning of CA4P treatments.

Objective: This study was designed to assess the potential of the nitroaromatic radiosensitizer doranidazole to preferentially enhance radiation-induced local control in a murine tumour., Methods: A C3H mammary carcinoma grown in the right rear foot of female CDF1 mice was used and treated when at 200 mm(3) in size. Doranidazole was dissolved in saline and injected intravenously. Radiation (240 kV X-rays) was locally administered to the tumours or normal feet of restrained non-anaesthetised animals. Response endpoints were local tumour control at 90 days and moist desquamation in foot skin 11-23 days after irradiation. Following logit analysis of the radiation dose-response curves the TCD50 (tumour) or MDD50 (skin) doses (radiation doses producing a response in 50% of treated mice) were estimated and a sensitizer enhancement ratio (SER; ratio of the TCD50 or MDD50 for radiation alone and radiation with drug) calculated. Statistical analysis was performed using a chi(2) test (p<0.05)., Results: The TCD50 value (+/-95% confidence interval) for radiation alone as a single treatment was 53Gy (51-55). Injecting doranidazole (200 mg/kg) at 0, 30 or 60 min prior to irradiation significantly enhanced radiation response with the greatest effect seen at the 30-min interval [TCD50=40Gy (37-44); SER=1.3]. No enhancement occurred when the drug was given after radiation. Injecting different drug doses 30 min prior to irradiation showed a dose-response relationship; the respective SERs were 1.1, 1.3 and 1.8 at 50, 200 and 500 mg/kg. In skin, using the 200mg/kg dose and a 30-min interval, the SER was only 1.1. Combining doranidazole and radiation in a fractionated schedule gave a tumour SER of 1.1., Conclusions: Non-toxic doses of doranidazole significantly enhanced tumour response to single radiation treatments, an effect that was greater than that seen in a normal tissue. It also enhanced radiation given in a fractionated schedule. These effects were similar to those found with misonidazole and nimorazole, nitroaromatic radiosensitizers with clinical efficacy.

Purpose: To determine how combretastatin A-4 disodium phosphate (CA4DP) dose-dependent changes in radiation response of a C3H mouse mammary carcinoma relate to measurements of dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters and how those mouse DCE-MRI results compare with published clinical DCE-MRI data., Methods and Materials: C3H mammary carcinomas grown in female CDF(1) mice were treated when at 200 mm(3) in size. Groups of mice were given graded radiation doses, either alone or followed 30 min later by an intraperitoneal injection of CA4DP, administered at doses of 10-250 mg/kg. The radiation dose producing local tumor control in 50% of treated animals at 90 days (TCD(50)) was calculated for each CA4DP dose. DCE-MRI was performed before and 3 h after CA4DP administration, and parameters describing vascularity and interstitial volume were estimated., Results: TCD(50) showed a dose-dependent decrease reaching significance at 25 mg/kg. At greater doses of 50 and 100 mg/kg, the TCD(50) increased slightly and was not significantly different from that of controls. TCD(50) significantly decreased again at 250 mg/kg. The drug dose-response curves for all post-treatment vascular DCE-MRI parameters showed a shape similar to that of the TCD(50) curve. A similar dose dependency was seen with previously published clinical data., Conclusion: Our preclinical DCE-MRI data could predict the CA4DP enhancement of the tumor radiation response and suggest the clinical CA4DP doses necessary to improve the radiation response in patients.

Introduction: Dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) allows in vivo characterization of tumour vasculature. As such, it is applicable for monitoring the effects of treatments targeting vasculature. The aims of this study were to evaluate the properties of tumour areas segmented-out by DCE-MRI parameters and to evaluate the changes induced by the vascular disrupting agent (VDA) combretastatin A-4 disodium phosphate (CA4DP), a leading VDA in clinical trials, in these areas., Material and Methods: Two tumour models previously shown to respond differently to CA4DP were chosen. The C3H mammary carcinoma and the KHT sarcoma were grown in the right rear foot of CDF(1) and C3H/km mice, respectively, and treated when at 200 or 800 mm(3) in size. DCE-MRI, using the contrast agent Gd-DTPA, was performed on a 7 T spectroscopy/imaging system before and 3 hours after i.p. CA4DP administration at a dose of 100 mg/kg. From the voxel concentration-time curves, the semiquantitative parameter of initial area under the curve (IAUC), the model parameters transfer constant K(trans), interstitial volume v(e), and blood plasma volume v(p), were calculated. Tumour images were segmented into three groups based on the DCE-MRI model parameters using the K-means algorithm, and the groups were ranked by IAUC., Results: The resulting voxels of the tumour segments were mainly spatially connected structures. Initial DCE-MRI parameter values showed different dependencies on tumour model and size in the regions. For all regions in all tumour groups, the treatment reduced IAUC by 36-51%, whereas the model parameters showed more dependencies on tumour model and size., Discussion: This segmentation technique identifies tumour regions with different microenvironmental characteristics responding differently to CA4DP and may be valuable in the optimization of combined VDA with radiotherapy or chemotherapy. The method may also prove useful for optimization and monitoring of local treatment such as radiotherapy.

Aim: To investigate the direct relationship between tumour hypoxia and lactate dehydrogenase (Ldh) levels in serum and tumour in two different pre-clinical murine models., Materials and Methods: Experiments were performed in CDF1 or C3H/ Km mice implanted with a C3H mammary carcinoma and SCCVII squamous cell carcinoma, respectively. Low oxygen breathing for 1-72 h was used to increase tumour hypoxia. Ldh activity was measured in the serum and tumour cytosole with a colorimetric method. Tumour Ldha mRNA levels were assessed with RT-PCR. RESULTS; The serum Ldh in non-tumour bearing CDF1 mice and C3H/km mice was 10.592 U/ml and 1292 U/ml, respectively. For C3H mammary carcinoma bearing mice, a positive correlation between tumour volume and tumour and serum Ldh was found. Tumour Ldh in SCCVII carcinomas also increased with increasing tumour volume, but no volume dependence of serum Ldh was found. Low oxygen breathing caused a 2-3 fold increase in tumour Ldha mRNA in both tumour models. In C3H mammary carcinoma bearing mice, serum and tumour Ldh significantly increased after 48 and 72 hours of hypoxia, respectively. Low oxygen breathing did not change serum and tumour Ldh in SCCVII carcinoma bearing mice. Reoxygenation for 4 or 24 hours had no additional effect on Ldh activity in any of the models., Discussion: Serum Ldh activity can be a marker for tumour burden in certain types of cancer. The relationship between serum and tumour Ldh and tumour hypoxia has not been confirmed. However, Ldha mRNA may be a potential new marker of tumour hypoxia and should be further investigated.

Purpose: To evaluate the effect of the vascular disrupting drugs combretastatin A-4 disodium phosphate (CA4DP) and 5,6-dimethylxanthenone-4-acetic acid (DMXAA) on the intra/extracellular volume fraction of water and blood perfusion in tumours using MRI., Methods and Materials: Mice with C3H mammary carcinomas underwent repeated MRI T2-weighted imaging, water-diffusion and perfusion measurements before and up to 6-hours following CA4DP and DMXAA treatment., Results: CA4DP treatment caused an increase in water diffusion in those tumour areas that presented the lowest blood perfusion, however this appeared only after five hours. The blood perfusion in highly perfused tumour regions decreased immediately after administration of CA4DP. DMXAA treatment caused an early decrease in water diffusion in the low-perfused tumour segments and followed by a subsequent decrease in the remaining part of the tumour. The blood perfusion decreased early in all parts of the tumour., Conclusion: The effect of CA4DP and DMXAA on tumour blood flow was comparable. The reduction in regional blood flow caused by CA4DP in the whole tumour segment occurred early, however, changes in ADC after DMXAA appeared more extended and earlier than after CA4DP treatment, especially in tumour areas already suffering from a low blood perfusion.

Combretastatin-A4 disodium phosphate (CA4DP) is a vascular-disruptive agent that causes an abrupt decrease in tumor blood flow. The direct actions of CA4DP include increases in vascular permeability and destabilization of the endothelial cytoskeleton, which are thought to contribute to occlusion of the tumor vasculature. It has been proposed that increased permeability causes a transient increase in interstitial fluid pressure (IFP), which in turn could collapse intratumoral blood vessels. We examined the immediate effects of CA4DP on tumor IFP in C3H mammary carcinoma. Mice were treated with 100 mg/kg CA4DP by intraperitoneal injection. Tumor perfusion was recorded by laser Doppler flowmetry at separate time points, and IFP was recorded continuously by the wick-in-needle method. In this study, we found that CA4DP treatment resulted in a rapid reduction in tumor perfusion, followed by a decrease in IFP; no increases in IFP were observed. This suggests that CA4DP-induced reductions in tumor perfusion are not dependent on increases in IFP.

Purpose: To investigate the relationship between tumour hypoxia and serum and tumour osteopontin (OPN) levels., Materials and Methods: Experiments were performed in CDF1 or C3H/Km mice implanted with a C3H mammary carcinoma (CDF1) or SCCVII squamous cell carcinoma (C3H/Km), respectively. Mice were either untreated or gassed with 10% oxygen for 1-72 h. Serum and tumour OPN levels were measured with an ELISA and tumour OPN mRNA levels using RT-PCR. Tumour oxygenation was estimated using the Eppendorf histograph with the percentage of pO(2) values

This study was designed to demonstrate a differential tumour response to radiation given as a large single dose or fractionated, and to investigate the postulated role of the tumour vasculature as a target for this difference. A C3H mammary carcinoma grown in the right rear foot of female CDF1 mice was used when at 200 mm3. Radiation (240 kV x-rays) was given locally to the tumour bearing foot either as 1 x 20 Gy or 10 x 2 Gy (2 fractions/day). Tumour response was assessed by calculating tumour growth time (TGT; time to grow to 3 times treatment volume). Vascular effects were monitored by performing dynamic contrast enhanced-magnetic resonance imaging using a 3-Tesla magnet and the contrast agent gadolinium (Gd)-DTPA. The endpoint was the initial area under the concentration curve (IAUC) following Gd-DTPA. The mean (+/-1 S.E.) TGT for control mice was 4.0 days (+/-0.2). This was significantly (Student's t-test; p < 0.05) increased to 12.9 (+/-0.6) and 19.8 (+/-0.7) days, by 10 x 2 and 1 x 20 Gy, respectively. The mean (+/-1 S.E.) of the median IAUC values for control tumours was 8.4 mMs (+/-0.5). This was non-significantly increased to 9.4 mMs (+/-0.4) 6-hours after 1 x 20 Gy, but then significantly decreased to a nadir of 6.8 mMs (+/-0.5) after 48-hours. IAUC recovered at longer time intervals. With 10 x 2 Gy, IAUC significantly decreased during irradiation, reaching 6.7 (+/-0.3) and 5.6 (+/-0.3) mMs at the mid-point and end of the irradiation period, respectively. IAUC recovered 24-hours after irradiating before significantly decreasing to 4.4 mMs (+/-0.3) at 48-hours. Our results confirm that radiation given in a large single dose is superior to the same dose given in a more conventional fractionated schedule, but vascular-mediated effects did not account for this difference in radiation sensitivity.

Background: Texture analysis can be used to identify and discriminate between objects in an image and has already been used for the characterization of diseases. The present study evaluated the potential of texture analysis for monitoring tumor cell viability during treatment with an anti-vascular drug., Materials and Methods: Texture analysis of T2-weighted magnetic resonance images of C3H mammary carcinomas in mice was used to study tumor cell viability during treatment with the anti-vascular drug combretastatin A-4 disodium phosphate (CA4DP). Texture analysis was done by MaZda, and boot strap statistics were used to analyze the results., Results: The results revealed significant differences in the textures of T2-weighted images when non-tumor tissue and tumor tissue were compared. Furthermore, selected texture parameters were significantly different when image data from before and after CA4DP administration were analyzed., Conclusion: Texture analysis is helpful in the diagnosis of different types of tissues, especially when these tissues can not be recognized by human observers. Some functional changes, such as perfusion changes in the tumor, can also be detected by texture analysis.

Purpose: To explore conflicting results obtained when tumor hypoxia is assessed with Eppendorf electrode Po(2) measurements and with positron emission tomography (PET) by use of [(18)F]fluoromisonidazole (FMISO)., Methods and Materials: We compared the 2 methods in conjunction with 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) PET, dual-tracer ex vivo autoradiography (FMISO and 2-deoxy-D-[1-(14)C]glucose (2DG)), and histology in 2 murine tumor models, the C3H mammary carcinoma and the SCCVII squamous cell carcinoma., Results: 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG)-PET showed tumor-to-reference tissue ratios of 3.5 in both tumor models after 2 hours. C3H mammary carcinoma reached an FMISO PET ratio of 11 after 3.5 hours. Autoradiography showed large confluent areas of FMISO and 2DG uptake. Median Po(2) was 7 mm Hg and necrotic fraction was 10% to 30%. SCCVII squamous-cell carcinoma reached an FMISO PET tumor-to-reference tissue ratio of 2 after 2.5 hours. Autoradiography showed homogeneous 2DG uptake and scattered foci of high FMISO uptake. Median Po(2) was 1 mm Hg and necrotic fraction was below 5%., Conclusions: Ex vivo dual-tracer autoradiography documented the ability of in vivo FMISO PET to distinguish between confluent areas of either viable tissue or necrosis. Electrode Po(2) measurements could not be ascribed to specific areas in the tumors. Less uptake of FMISO in SCCVII squamous-cell carcinoma than in C3H mammary carcinoma could be caused by scattered foci versus confluent areas of viable hypoxic tissue in the 2 tumors, respectively.

Purpose: To examine the feasibility of using the MRI blood pool agent NC100150 for evaluation of tumor blood volume (TBV) estimates by both dynamic contrast-enhanced MRI (DCE-MRI) and susceptibility contrast MRI assays in an experimental tumor. Contrast agent clearance (K(trans); depends on perfusion and permeability) from the DCE-MRI time curves was estimated, and changes in TBV and K(trans) were measured after administration of two drugs that reduce perfusion by different mechanisms., Methods and Materials: The DCE-MRI experiments were simulated with expected physiologic values for the C3H mouse mammary carcinoma. The C3H tumor was examined by DCE-MRI and susceptibility contrast MRI with NC100150 (NC100150 Injection, Clariscan; Amersham Health, Oslo, Norway) after treatment with either hydralazine or combretastatin (Oxigene, Boston, MA)., Results: Simulations showed that reliable estimates of changes in TBV and K(trans) could be performed with DCE-MRI. Hydralazine was shown to reduce TBV as measured by both assays and to reduce K(trans). Dynamic contrast-enhanced MRI also suggested that TBV and K(trans) were reduced in combretastatin-treated tumors, and the TBV reduction was confirmed by susceptibility contrast MRI. Data suggested the drug to affect mainly the total TBV, whereas microvessels as such seemed less altered., Conclusion: The study supports the use of the combined DCE-MRI and susceptibility contrast MRI assay with a blood pool agent in characterizing tumors and their response to treatment.

The first aim of this study was to compare the hypoxia imaging ability of fluorine-18 fluoroerythronitroimidazole ([18F]FETNIM) with that of fluorine-18 fluoromisonimidazole ([18F]FMISO) in murine tumours of different sizes under two different oxygenation conditions. Secondly, we wanted to assess the biodistribution of the markers in normal tissues under similar conditions. Female CDF1 mice with a C3H mammary carcinoma grown on their backs were used. Tumours were size matched and animals breathed either normal air (21% O(2)) or carbogen gas (95% O(2) + 5% CO(2)). The gassing procedure was begun 5 min before the intravenous injection of either [18F]FETNIM or [18F]FMISO and continued until the mice were sacrificed at 120 min. Blood, tumour, muscle, heart, lung, liver, kidney and fat were removed, counted for radioactivity and weighed. The tumour and muscle were frozen and cut with a cryomicrotome into sections. The spatial distribution of radioactivity from the tissue sections was determined with digital autoradiography. Estimation of the necrotic fraction was made on sections from formalin-fixed tumours. Digital autoradiography showed that the whole tumour-to-muscle radioactivity uptake ratios were significantly higher in normal air-breathing mice than in carbogen-treated mice for both [18F]FETNIM (4.9+/-2.6 vs 1.8+/-0.5; P<0.01) and [18F]FMISO (4.4+/-1.0 vs 1.5+/-0.4; P<0.01). The carbogen treatment had only slight effects on the biodistribution of either marker in normal tissues. The necrotic fraction determined in tumours did not correlate with the tumour volume or with the tumour-to-muscle radioactivity uptake ratio. This study shows that the uptake of both [18F]FETNIM and [18F]FMISO correlates with the oxygenation status in tumours. In addition, our data show no significant difference in the intratumoral uptake between the two markers. However, significantly higher radioactivity uptake values were measured for [18F]FMISO than for [18F]FETNIM in normal tissues.

Background and Purpose: Accelerated radiation carbogen nicotinamide (ARCON) therapy is generally well tolerated, but some patients experience intolerance to nicotinamide and carbogen (95% O(2)+5% CO(2)). This study investigated the effect of reducing both the nicotinamide dose and carbogen CO(2) content on radiation response., Materials and Methods: A C3H mouse mammary carcinoma grown in the right rear foot of female CDF1 was used and treated when at 200 mm(3). Nicotinamide was intraperitoneally injected 20 min prior to irradiation. Carbogen (CO(2) content of either 2 or 5%, balance O(2)) breathing was started 5 min before, and continued during, additional treatments. Radiation was given locally to tissues of restrained non-anaesthetised mice either as a single or fractionated (10 fractions in 12 days) schedule. The endpoints were local tumour control at 90 days, development of moist desquamation 11-23 days after treatment of normal foot skin, or tumour oxygenation measured with the Eppendorf electrode., Results: The TCD50 values in this tumour following single or fractionated radiation treatment were 52 and 71Gy, respectively. Carbogen (5% CO(2) content) breathing with every radiation treatment in the fractionated schedule significantly (Chi-squared test; P<0.05) enhanced radiation response (ER 1.25). Significant enhancements were also seen with nicotinamide given either as 10x120 mg/kg (ER 1.25), 6x120 mg/kg (ER 1.11) or 10x90 mg/kg (ER 1.18), although the 6x120 schedule was significantly less effective than 10x120. Combining nicotinamide with carbogen resulted in ERs of 1.39-1.44, and these were independent of the nicotinamide treatments. There was also no significant difference in the enhancement of tumour radiation response or improved tumour oxygenation status if the CO(2) content of the gas breathing was varied from 0% (i.e. 100% O(2)) to 2 or 5% (balance O(2)), although a CO(2) content of 2% did give a smaller enhancement of radiation-induced normal skin damage than 5%., Conclusions: Both the nicotinamide dose, but not the frequency, and carbogen CO(2) content may be reduced in patients experience intolerance without any significant loss of sensitisation.

Purpose: The aim of this study was to investigate the pathophysiologic effects induced by the novel vascular targeting agent ZD6126 in a C3H mouse mammary carcinoma and to evaluate the agent's ability to inhibit tumor growth either when given alone or in combination with radiation., Methods and Materials: A C3H mammary carcinoma grown in the right rear foot of female CDF1 mice was treated when at 200 mm(3) in size. ZD6126 was dissolved in saline and injected intraperitoneally. Blood perfusion was measured using the RbCl extraction procedure, tumor oxygen (pO(2)) status was assessed with the Eppendorf electrode, and tumor necrosis was estimated from histologic sections. Radiation (240-kV X-rays) was locally administered to tumors of restrained nonanesthetized mice, and response was assessed using a tumor growth assay., Results: ZD6126 induced a significant dose- and time-dependent decrease in tumor perfusion, reaching a maximal 70% reduction around 3 h after injecting 150-300 mg/kg. However, full recovery was seen within 6 h. A 200 mg/kg dose significantly decreased tumor oxygenation status at 3 h (median pO(2) decreased from 7 to 3 mm Hg; % pO(2) values

The aim of this study was to compare a non-invasive 18F-fluoromisonidazole ([18F]FMISO) PET assessment of tumour hypoxia with invasive Eppendorf pO2 measurements in 150-1,500 mm3 C3H mammary carcinomas transplanted on the back of CDF1 mice. The tumour-bearing mice breathed either carbogen gas (95% oxygen, 5% CO2) or normal air during both examinations. Additional autoradiography was performed in separate tumours treated similarly. The PET [18F]FMISO examination significantly discriminated between tumours of carbogen and air-breathing mice. For the pO2 measurements, there was a significantly lower percentage of measurements below 2.5 mmHg for carbogen-treated mice compared with air-breathing mice. However, no direct correlation between the methods was seen. A correlation was found between tumour volume and Eppendorf estimates of tumour hypoxia for the animals breathing normal air, but no correlation was found between the PET endpoint and tumour volume. This may be due to low pO2 measurements obtained in necrotic tissue. Autoradiography confirmed lower [18F]FMISO uptake in tumours of carbogen-breathing animals compared with air-breathing animals, and demonstrated the heterogeneity of the tracer uptake in small compared with larger tumours.