Effect of calcitonin gene related peptide vs sodium nitroprusside to increase temperature in spontaneous canine tumours during local hyperthermia.

The objectives of this study were to compare the effects of two vasodilators, sodium nitroprusside (SNP) and calcitonin gene-related peptide (CGRP) on mean arterial pressure (MAP), heart rate (HR) and temperatures in tumour and surrounding normal tissue during local hyperthermia treatment. Eleven tumour-bearing pet dogs with spontaneous soft tissue sarcomas were given SNP intravenously during local hyperthermia. The drug infusion rate was adjusted to maintain a 20% decrease in MAP. The median (95% CI) increase in the temperature distribution descriptors T(90) and T(50) was 0.2 degrees C (0.0-0.4 degrees C, p = 0.02) and 0.4 degrees C (0.1-0.7 degrees C, p = 0.02), respectively, in tumour. Normal subcutaneous tissue temperatures were mildly increased but remained below the threshold for thermal injury. The effects of CGRP were investigated in six tumour-bearing dogs following a protocol similar to that used for SNP. The median (interquartile (IQ) range) decrease in mean arterial pressure was 19% (15-26%) after CGRP administration and a significant increase was seen in tumour but not normal subcutaneous tissue temperatures. The median (95% CI) increase in the temperature distribution descriptors T(90) and T(50) was 0.5 degrees C (0.1-1.6 degrees C, p = 0.03) and 0.8 degrees C (0.1-1.6 degrees C, p = 0.13), respectively. Administration of SNP or CGRP did not result in local or systemic toxicity in tumour-bearing dogs. However, the magnitude of increase in tumour temperatures was not sufficient to improve the likelihood of increased response rates. Therefore, there is little justification for translation of this approach to human trials using conventional local hyperthermia.

Temperature-dependent changes in physiologic parameters of spontaneous canine soft tissue sarcomas after combined radiotherapy and hyperthermia treatment.

PURPOSE: The objectives of this study were to evaluate effects of hyperthermia on tumor oxygenation, extracellular pH (pHe), and blood flow in 13 dogs with spontaneous soft tissue sarcomas prior to and after local hyperthermia. METHODS AND MATERIALS: Tumor pO2 was measured using an Eppendorf polarographic device, pHe using interstitial electrodes, and blood flow using contrast-enhanced magnetic resonance imaging (MRI). RESULTS: There was an overall improvement in tumor oxygenation observed as an increase in median pO2 and decrease in hypoxic fraction (% of pO2 measurements <5 mm Hg) at 24-h post hyperthermia. These changes were most pronounced when the median temperature (T50) during hyperthermia treatment was less than 44 degrees C. Tumors with T50 > 44 degrees C were characterized by a decrease in median PO2 and an increase in hypoxic fraction. Similar thermal dose-related changes were observed in tumor perfusion. Perfusion was significantly higher after hyperthermia. Increases in perfusion were most evident in tumors with T50 < 44 degrees C. With T50 > 44 degrees C, there was no change in perfusion after hyperthermia. On average, pHe values declined in all animals after hyperthermia, with the greatest reduction seen for larger T50 values. CONCLUSION: This study suggests that hyperthermia has biphasic effects on tumor physiologic parameters. Lower temperatures tend to favor improved perfusion and oxygenation, whereas higher temperatures are more likely to cause vascular damage, thus leading to greater hypoxia. While it has long been recognized that such effects occur in rodent tumors, this is the first report to tie such changes to temperatures achieved during hyperthermia in the clinical setting. Furthermore, it suggests that the thermal threshold for vascular damage is higher in spontaneous tumors than in more rapidly growing rodent tumors.

Acute pancreatitis associated with administration of a nitric oxide synthase inhibitor in tumor-bearing dogs.

BACKGROUND: Nitric oxide synthase (NOS) inhibitors have been investigated as potential cytotoxic agents to treat tumors lacking p53 function. Furthermore, their ability to reduce tumor blood flow can be combined with drugs that are specifically designed to kill cells that are hypoxic or to improve temperatures during local heat (hyperthermia) treatment of tumors. This paper reports the unexpected development of acute pancreatitis in two tumor-bearing pet dogs that were treated with the NOS inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) during administration of local hyperthermia. METHODS: Prior to the use of L-NAME in tumor-bearing dogs, purpose-bred beagles were studied. Following induction of inhalation anesthesia, local hyperthermia was applied to either normal thigh muscle (beagles) or tumors (tumor-bearing dogs). Once a thermal steady state was achieved, L-NAME was administered and temperature monitoring continued. Animals were observed after treatment for evidence of toxicity. RESULTS: The beagles tolerated the treatment well, with no side effects noted either clinically or by routine CBC or blood chemistry analyses. In contrast, the first two tumor-bearing dogs accrued onto the phase I study developed acute pancreatitis in the immediate post-treatment period which necessitated hospitalization and intensive care. The trial was stopped. Both dogs had intercurrent risk factors which predisposed them to development of pancreatitis, although neither had a history of symptoms of pancreatitis at the time the hyperthermia + L-NAME treatment was given. CONCLUSIONS: We conclude that caution should be exercised when considering NOS inhibition for cancer treatment. Careful evaluation of history and health status as well as recognition of potential risk factors may be key in avoiding potentially fatal complications. This study demonstrates the value of performing potentially harmful treatments in tumor-bearing dogs prior to introduction into the human clinic.

Magnetic resonance thermometry during hyperthermia for human high-grade sarcoma.

PURPOSE: To determine the feasibility of measuring temperature noninvasively with magnetic resonance imaging during hyperthermia treatment of human tumors. METHODS: The proton chemical shift detected using phase-difference magnetic resonance imaging (MRI) was used to measure temperature in phantoms and human tumors during treatment with hyperthermia. Four adult patients having high-grade primary sarcoma tumors of the lower leg received 5 hyperthermia treatments in the MR scanner using an MRI-compatible radiofrequency heating applicator. Prior to each treatment, an average of 3 fiberoptic temperature probes were invasively placed into the tumor (or phantom). Hyperthermia was applied concurrent with MR thermometry. Following completion of the treatment, regions of interest (ROI) were defined on MR phase images at each temperature probe location, in bone marrow, and in gel standards placed outside the heated region. The median phase difference (compared to pretreatment baseline images) was calculated for each ROI. This phase difference was corrected for phase drift observed in standards and bone marrow. The observed phase difference, with and without corrections, was correlated with the fiberoptic temperature measurements. RESULTS: The phase difference observed with MRI was found to correlate with temperature. Phantom measurements demonstrated a linear regression coefficient of 4.70 degrees phase difference per degree Celsius, with an R2 = 0.998. After human images with artifact were excluded, the linear regression demonstrated a correlation coefficient of 5.5 degrees phase difference per degree Celsius, with an R2 = 0.84. In both phantom and human treatments, temperature measured via corrected phase difference closely tracked measurements obtained with fiberoptic probes during the hyperthermia treatments. CONCLUSIONS: Proton chemical shift imaging with current MRI and hyperthermia technology can be used to monitor and control temperature during treatment of large tumors in the distal lower extremity.

Hyperthermic treatment of malignant diseases: current status and a view toward the future.

New studies in hyperthermia at the basic science, engineering, and clinical level have stimulated renewed enthusiasm for re-investigating its potential as an anticancer therapy. This article reviews the salient features of these recent results and points out areas for additional investigation. Highlighting these new results is the publication of several positive phase III trials for thermoradiotherapy compared to radiotherapy alone. Important highlights are the encouraging results using magnetic resonance imaging for noninvasive thermometry. If this technology is successfully implemented with real time power control it will revolutionize the clinical application of hyperthermia.

1H MRI phase thermometry in vivo in canine brain, muscle, and tumor tissue.

The temperature sensitivity of the chemical shift of water (approximately 0.01 ppm/degree C) provides a potential method to monitor temperature changes in vivo or in vitro through the changes in phase of a gradient-echo magnetic resonance (MR) image. This relation was studied at 1.5 T in gel materials and in vivo in canine brain and muscle tissue, heated with a radio frequency (rf) annular phased array hyperthermia antenna. The rf fields associated with heating (130 MHz) and imaging (64 MHz) were decoupled using bandpass filters providing isolation in excess of 100 dB, thus allowing simultaneous imaging and rf heating without deterioration of the MR image signal-to-noise ratio. In a gel, temperature sensitivity of the MR image phase was observed to be (4.41 +/- 0.02) phase degrees/degree C for Te = 20 ms, which allowed temperature changes of 0.22 degree C to be resolved for a 50-mm3 region in less than 10 s of data acquisition. In vivo, for Te = 20 ms, the temperature sensitivity was (3.2 +/- 0.1) phase degrees/degree C for brain tissue, (3.1 +/- 0.1) phase degrees/degree C for muscle, and (3.0 +/- 0.2) phase degrees/degree C for a muscle tumor (sarcoma), allowing temperature changes of 0.6 degree C to be resolved in a 16-mm3 volume in less than 10 s of data acquisition. We conclude that, while the technique is very sensitive to magnetic field inhomogeneity, stability, and subject motion, it appears to be useful for in vivo temperature change measurement.

Monitoring of neoadjuvant therapy response of soft-tissue and musculoskeletal sarcoma using fluorine-18-FDG PET.

UNLABELLED: The purpose of this study was to investigate the potential role of FDG-PET in the monitoring of neoadjuvant therapy of soft-tissue and musculoskeletal sarcomas. METHODS: Nine patients were studied. Neoadjuvant therapy consisted of either chemotherapy or combined radiotherapy and hyperthermia. The FDG-PET studies were obtained, when possible, prior to therapy, 1-3 wk after commencement of therapy, and prior to surgery after completion of neoadjuvant therapy. In two patients, all three studies were completed. The remainder of patients underwent one or two studies at varying timepoints. RESULTS: In tumors treated with combined radiotherapy and hyperthermia, well-defined regions of absent uptake developed within responsive tumors, correlating pathologically with necrosis. Following treatment, a peripheral rim of FDG accumulation was found to correlate pathologically with the formation of a fibrous pseudocapsule. In tumors treated with chemotherapy, FDG accumulation decreased more homogeneously throughout the tumor, in responsive cases. Despite 100% tumor cell kill in some patients, persistent tumor FDG uptake was observed which correlated pathologically with uptake within benign therapy-related fibrous tissue. Significant FDG accumulation was also observed at the site of an uncontaminated incisional biopsy. CONCLUSION: These initial results demonstrate changes in tumor accumulation of FDG during and after neoadjuvant therapy; these changes are dependent on the type of neoadjuvant therapy administered. Prominent FDG accumulation was observed in benign tissues both within and adjacent to the treated tumor.

Radiation plus local hyperthermia versus radiation plus the combination of local and whole-body hyperthermia in canine sarcomas.

PURPOSE: The purpose of this study was to assess the effect of increasing intratumoral temperatures by the combination of local hyperthermia (LH) and whole body hyperthermia (WBH) on the radiation response of canine sarcomas. METHODS AND MATERIALS: Dogs with spontaneous soft tissue sarcomas and no evidence of metastasis were randomized to be treated with radiation combined with either LH alone or LH + WBH. Dogs were accessioned for treatment at two institutions. The radiation dose was 56.25 Gy, given in 25 2.25 Gy daily fractions. Two hyperthermia treatments were given; one during the first and one during the last week of treatment. Dogs were evaluated after treatment for local recurrence, metastasis, and complications. RESULTS: Sixty-four dogs were treated between 1989 and 1993. The use of LH+WBH resulted in statistically significant increases in the low and middle regions of the temperature distributions. The largest increase was in the low temperatures with median CEM 43 T90 values of 4 vs. 49 min for LH vs. LH + WBH, respectively (p<0.001). There was no difference in duration of local tumor control between hyperthermia groups (p = 0.59). The time to metastasis was shorter for dogs receiving LH + WBH (p = 0.02); the hazard ratio for metastatic disease for dogs in the LH + WBH group was 2.4 (95% confidence interval, 1.2-5.4) with respect to dogs in the LH group. Complications were greater in larger tumors and in tumors treated with LH + WBH, CONCLUSION: The combination of LH + WBH with radiation therapy, as described herein, was not associated with an increase in local tumor control in comparison to use of LH with radiation therapy. The combination of LH + WBH also appeared to alter the biology of the metastatic process and was associated with more complications than LH. We identified no rationale for further study of LH + WBH in combination with radiation for treatment of solid tumors.

Temperature dependence of canine brain tissue diffusion coefficient measured in vivo with magnetic resonance echo-planar imaging.

The intensity of conventional spin-echo diffusion-weighted magnetic resonance (MR) images is approximately linearly dependent on temperature over a restricted range using conventional diffusion-weighted spin-echo magnetic resonance imaging (MRI). However, conventional diffusion-weighted MRI is too motion sensitive for in vivo thermometry. The present work evaluated rapid diffusion-weighted echo-planar imaging (EPI), which is less sensitive to motion, for application to non-invasive thermometry in acrylamide gel materials and in vivo in canine brain tissue for applications in therapeutic hyperthermia. The rapidly switched, strong gradients needed for EPI were achieved using a 'local' z-axis gradient coil. Gel materials were heated with a small (10 cm diameter) spiral surface microwave (MW) applicator at 433 MHz, while in vivo heating was accomplished with whole body RF hyperthermia using an annular phased array (130 MHz). The MW or RF fields associated with heating and imaging (64 MHz) were decoupled using bandpass filters providing isolation in excess of 100 dB. This isolation was sufficient to allow simultaneous imaging and MW or RF heating without deterioration of the image signal-to-noise ratio. Using this system in a gel, temperature sensitivity of the diffusion coefficient was observed to be (3.04 +/- 0.03)%/degrees C which allowed temperature changes of 0.55 degrees C to be resolved for a 1.8 cm3 region in < 10 s of data acquisition. In vivo, cardiac gating of the pulse sequence was necessary to minimize motion artifacts in the brain. The temperature sensitivity of brain tissue was (1.9 +/- 0.1)%/degrees C allowing temperature changes of 0.9 degrees C to be resolved in a 0.9 cm3 volume in < 10 s of data acquisition. We conclude that with further optimization of the data acquisition conditions it will be possible to determine 0.5 degrees C temperature changes in 1 cm3 volumes in < 10 s using this technique.

Application of new technology in clinical hyperthermia.

Two areas of technical progress related to hyperthermic oncology are presented: (1) numerical modelling of absorbed power and temperature distributions; and (2) non-invasive thermometry using magnetic resonance imaging. The results represent achievements made during the past 5 years at Duke University Medical Center's Departments of Radiation Oncology and Radiology. They represent examples of progress in the technology of hyperthermia that have potential for greatly improving the delivery, monitoring and assessment of clinical hyperthermia.

Therapy monitoring in human and canine soft tissue sarcomas using magnetic resonance imaging and spectroscopy.

PURPOSE: The goals of this study were to determine whether magnetic resonance parameters (a) can identify early during therapy those patients most likely to respond to hyperthermia and radiotherapy, (b) can provide prior to or early during therapy information about the temperature distributions which can be obtained in patients receiving hyperthermia, and (c) can provide an understanding of the effects of hyperthermia on tumor metabolic status. METHODS AND MATERIALS: Twenty-one human patients and 10 canine patients with soft tissue sarcomas treated with preoperative hyperthermia and radiation had a series of magnetic resonance imaging and phosphorous spectroscopy studies done. To address the goals for both the human and canine populations, changes in mean T2 relaxation times, pH, and various phosphometabolite ratios from the pretreatment (Study 1) to the post first hyperthermia study (Study 2) were correlated with treatment outcome; pretreatment magnetic resonance parameters and changes in magnetic resonance parameters (Study 2-Study 1) were compared with various cumulative thermal descriptors; and thermal descriptors of the first hyperthermia were compared with changes in magnetic resonance phosphometabolite ratios. RESULTS: A decrease in adenosine triphosphate/phosphomonoester from study 1 to study 2 is associated with a greater chance of > or = 95% necrosis in surgical resected tumors from human patients, but no significant relationships were observed between changes in tumor pH or phosphometabolite ratios and time to local failure in dogs. Pretreatment magnetic resonance parameters correlated with various thermal dose descriptors in canines but not in humans. Change in adenosine triphosphate/inorganic phosphate and phosphomonoester signal to noise ratio correlated with cumulative thermal descriptors in dogs and humans, respectively. In dogs only, increases in thermal dose resulted in decreases in high energy phosphometabolites. CONCLUSION: Changes in magnetic resonance parameters early during therapy may be predictive of treatment outcome. Pretreatment and changes in magnetic resonance parameters appear to predict how well a tumor will be heated during hyperthermia. Magnetic resonance spectroscopy also appears to be a useful tool to study the effects of various thermal doses on tumor metabolic status.

Manipulation of intra- and extracellular pH in spontaneous canine tumours by use of hyperglycaemia.

We evaluated the use of hyperglycaemia to reduce tumour pH in dog with spontaneous tumours. Dogs were randomized to two groups: control and glucose. Intravenous administration of 20% glucose was used to induce and maintain hyperglycaemia. Extra- and intracellular tumour pH were measured using interstitial pH microelectrodes and 31P-MRS, respectively. During the administration of glucose, the mean (+/- SEM) blood glucose concentration was 419.8 (+/- 32.8) and 121.1 (+/- 8.0) mg/dl for the glucose and control groups, respectively. The mean extracellular tumour pH before and following 90 min of hyperglycaemia was 7.15 (+/- 0.08) and 7.15 (+/- 0.09). During consecutive measurements, intracellular tumour pH did not change significantly for the control group or the group subjected to hyperglycaemic manipulation. In contradistinction to previous rodent studies, our results demonstrate that hyperglycaemia alone is not sufficient to manipulate either intra- (pHi) or extracellular (pHe) hydrogen ion concentration in spontaneous canine soft tissue tumours.

Hyperthermia-induced enhancement of melphalan activity against a melphalan-resistant human rhabdomyosarcoma xenograft.

The effects of regional hyperthermia (42 degrees C for 70 min) on the antitumor activity of melphalan were examined in athymic mice bearing melphalan-resistant human rhabdomyosarcoma (TE-671 MR) xenografts growing in the right hind limb, and results were compared with similar studies of melphalan-sensitive (TE-671) parent xenografts. Melphalan alone at a dose of 36 mg/m2 (0.5 of the 10% lethal dose) produced growth delays of 4.1 to 10.2 days in TE-671 MR xenografts and 21.8 to 28.7 days in TE-671, respectively. Hyperthermia alone produced growth delays of 0.9 days in TE-671 MR xenografts and 0.8 days in TE-671. Combination therapy with melphalan and hyperthermia produced growth delays of 7.2 to 13.3 days in TE-671 MR xenografts and 34.3 to 42.8 days in TE-671, respectively, representing a mean thermal enhancement ratio of 1.7 in TE-671 MR and 1.5 in TE-671. Measurement of glutathione levels in TE-671 MR xenografts following treatment with melphalan, hyperthermia, or melphalan plus hyperthermia revealed significant reductions in glutathione content with the nadir (60% of control values) seen 6 h following treatment. Glutathione levels in TE-671 xenografts following identical therapy revealed no differences from control values. Hyperthermia plus melphalan did not result in a higher tumor-to-plasma melphalan ratio compared with treatment with melphalan alone in either TE-671 MR or TE-671 xenografts. These studies suggest that heat-induced alterations in tumor glutathione or melphalan levels are not responsible for the increase in melphalan activity produced by hyperthermia. Combination therapy with melphalan plus regional hyperthermia offers promise for treatment of melphalan-resistant neoplasms.

Serious toxicity associated with annular microwave array induction of whole-body hyperthermia in normal dogs.

Using a regional annular microwave array it was possible to produce a systemic temperature of 42 degrees C in approximately 80 min with applied net power levels of approximately 150 W. Resulting temperature distributions were non-uniform. Sites within the array were above systemic temperature during heating but approximated systemic temperature during the plateau phase. Sites outside of the array were lower than systemic temperature during heating and plateau phases. Dogs allowed to recover from the procedure experienced severe toxicity consisting of lumbar muscle haemorrhage, pain and swelling, and pelvic limb paralysis. Histologically, there was severe myopathy and haemorrhage and oedema in neural tissue in the caudal lumbar spine. Acute necrosis of lymphoid tissue was observed in all dogs. Temperatures in muscle reached 43-46 degrees C and were higher than at other measured sites. Spinal canal temperatures were essentially equal to rectal temperature, approximating 42-43 degrees C during heating and plateau phases. These data suggest regionally induced whole-body hyperthermia may result in: (1) power deposition non-uniformity leading to muscle and spinal canal temperatures which exceed systemic temperature and which are sufficient to cause serious toxicity; (2) systemic temperature non-uniformity which is undesirable for systemic thermochemotherapy; and (3) possible immunological dysfunction associated with lymphoid necrosis. Extreme caution must be exercised in administering energy to localized regions of human patients with the intent of elevating systemic temperature.

Use of nitroprusside to increase tissue temperature during local hyperthermia in normal and tumor-bearing dogs.

The present study investigates the effects of nitroprusside, a potent vasodilating agent, on tissue temperature during local hyperthermia in five normal and five tumor-bearing dogs. Caudal thigh muscles were heated in normal dogs and muscle temperatures were recorded during hyperthermia. Tumor-bearing dogs received two hyperthermia treatments during a course of radiation therapy. Temperatures were recorded in tumor and surrounding normal tissues. Mean arterial pressure was decreased by approximately 40-45% during nitroprusside infusion and was associated with a compensatory increase in heart rate and increases in tissue temperature. In normal dogs, muscle temperatures increased an average of 1.7 degrees C with nitroprusside administration. When nitroprusside was administered at the beginning of local hyperthermia to induce step-down heating, approximately 48% of the measured positions in caudal thigh muscle achieved a temperature greater than or equal to 43 degrees C, sufficient to induce step-down heating, during the hyperthermia episode. In tumor-bearing dogs, there was a significant increase in tumor and normal tissue temperatures during nitroprusside administration. Estimated T90 and T50 descriptors increased by 0.9 degrees C and 1.6 degrees C, respectively, for tumor tissue and by 0.4 degrees C and 1.2 degrees C, respectively, for normal tissue. Despite the increase in normal tissue temperatures no toxicity was observed in these dogs. Nitroprusside may be a useful agent for manipulation of tumor temperatures during the entire hyperthermia treatment or for a short time period at the initiation of treatment to induce step-down heating.

Inhibition of telomerase by G-quartet DNA structures.

The ends or telomeres of the linear chromosomes of eukaryotes are composed of tandem repeats of short DNA sequences, one strand being rich in guanine (G strand) and the complementary strand in cytosine. Telomere synthesis involves the addition of telomeric repeats to the G strand by telomere terminal transferase (telomerase). Telomeric G-strand DNAs from a variety of organisms adopt compact structures, the most stable of which is explained by the formation of G-quartets. Here we investigate the capacity of the different folded forms of telomeric DNA to serve as primers for the Oxytricha nova telomerase in vitro. Formation of the K(+)-stabilized G-quartet structure in a primer inhibits its use by telomerase. Furthermore, the octanucleotide T4G4, which does not fold, is a better primer than (T4G4)2, which can form a foldback structure. We conclude that telomerase does not require any folding of its DNA primer. Folding of telomeric DNA into G-quartet structures seems to influence the extent of telomere elongation in vitro and might therefore act as a negative regulator of elongation in vivo.