A histopathologic study on the effects of radiofrequency thermotherapy on malignant tumors of the lung

Fever-Inducible Lipid Nanocomposite for Boosting Cancer Therapy through Synergistic Engineering of a Tumor Microenvironment

A fever-mimic response capable of recruiting reprogrammed macrophages holds great potential in the engineering of the tumor microenvironment (TME). Low-temperature photothermal therapy (LT-PTT) can maintain tumors at a fever-like temperature (<45 °C) temporarily; however, it still faces several challenges in efficient regulation of TME because of reciprocal cross-talk between the bypass pathways. Here, we report a synergistic engineering of TME through an enhanced activation of a fever-mimic response based on both LT-PTT and tumor vascular normalization. Such engineering is achieved by a fever-inducible lipid nanocomposite (GNR-T/CM-L), which produces mild heat (∼43 °C) and sequentially releases multicomponents to cooperatively upregulate interferon-gamma under NIR irradiation, forming a bidirectionally closed loop for downstream M1 tumor-associated macrophage polarization and promoting the inhibition of the tumor growth. In proof-of-concept studies, GNR-T/CM-L demonstrated efficient tumor ablation in breast tumor xenograft-bearing mice and significantly prolonged their survival period. It paves an avenue to precisely reprogram TME for efficient cancer therapy through synergistic pathways of creating fever-like responses in the tumor.

The blood cells in NSCLC and the changes after RFA

Lung cancer has attracted a lot of attention because of its high morbidity and mortality. The emergence of RFA provides a new treatment for unresectable NSCLC patients. In addition to killing in situ lung tumors, RFA also provides new immuno-activated antigens, for the treatment of lung cancer. It changes the tumor microenvironment and activates the entire immune system of patients. The peripheral blood cell count is easy to achieve and the blood cells are important in tumor immunity, which changes after RFA. On the one hand, the changes in blood cells identify the immune changes of NSCLC; on the other hand, it provides support and suspicion for the treatment of RFA.

Assessment of Toxicity and Therapeutic Effects of Goose Bone in a Rat Model

Goose bone is traditionally used in the treatment of many ailments including in bone fracture. The aim of the present study was to evaluate the subacute toxicity of goose bone in a rat model by investigating some hematological and biochemical parameters in rats. Subsequently, a histopathological study was performed to confirm the presence of pathological lesions in the rat’s vital organs including the liver, kidney, heart, brain, pancreas, lung, spleen, and stomach. Adult Wistar rats were divided into four groups (n = 8) and were orally administrated with three doses (30, 60, and 120 mg/kg) of goose bone once daily for 21 days as compared to control animals (received only drinking water). Goose bone did not cause any significant changes on body weight, relative organ weight, and percentage water content at any of the administered doses. There were also no significant alterations in hematological parameters seen. All three doses administered significantly reduced the triglyceride levels as well as the atherogenic index of plasma (AIP). Animals treated with 120 mg/kg doses had significantly reduced alkaline phosphatase (ALP) activity as compared to the control group. There was no significant alteration on other serum biochemical parameters seen. Additionally, histopathological findings confirmed that there was no inflammatory, necrotic, or other toxicological feature seen for all three doses. It is concluded that goose bone is nontoxic and is safe for consumption besides having the potential to be investigated for the treatment of high triglycerides or liver-related disorder.

A New Coaxial TEM Radiofrequency/Microwave Applicator for Non-Invasive Deep-Body Hyperthermia

At the moment great efforts are being made to develop non-invasive heating systems which produce controlled local or regional deep-body hyperthermia. Electromagnetic interference techniques (10-80 MHz) with several separated applicators or with multiple applicators can produce deep-body heating. In our institute a coaxial frequency-independent TEM radiofrequency/microwave applicator has been designed. This applicator can produce a theoretically optimal interference maximum in the centre of the body. The applicator is very simple to construct and inexpensive. To test the design with the equipment available, a scaled prototype of the TEM applicator has been developed. The prototype has a diameter of 20 cm and operates at 434 MHz. The applicator has been tested on several phantom materials. The measured absorbed power distributions are in good agreement with the calculated theoretical distributions. The theoretical calculations of the absorbed power distributions of a 10-80 MHz TEM deep-body applicator are very encouraging.

Radiofrequency Ablation: Emerging Therapy for the Small Pulmonary Nodule?

Traditional approaches to small pulmonary nodules have ranged from serial radiographic surveillance to transthoracic needle aspiration to surgical resection for diagnosis. Once the diagnosis of non-small-cell lung cancer is secured, lobectomy remains the gold standard treatment. Nevertheless, advances in image-guided technology and radiofrequency thermal ablation techniques have allowed for diagnostic sampling of lesions with concomitant therapeutic thermal ablation. The role these techniques will play in the treatment of patients with primary lung cancer remains undefined. This review (1) examines the basic technology of radiofrequency ablation; (2) provides an update on current clinical experience with this technique; and (3) explores the role of radiofrequency ablation in the treatment scheme of patients with non-small-cell lung cancer.

Clinical applications of radio-frequency tumor ablation in the thorax

Minimally invasive alternatives to surgery for the treatment of malignancy are becoming more attractive owing to improvements in technology, reduced morbidity and mortality, and the ability to provide treatment in an outpatient setting. Radio-frequency (RF) ablation has become the imaging-guided ablative method of choice because of its relatively low cost, its capability of creating large regions of coagulative necrosis in a controlled fashion, and its relatively low toxicity. RF ablation in the thorax involves the use of computed tomography (CT) to localize the tumor and determine the optimal approach. The size of the tumor determines whether a cluster of electrodes or a single electrode of a particular length will be used to perform the ablation. CT fluoroscopy aids in guiding placement of the electrode. In patients with non-small cell lung malignancy who are not candidates for surgery owing to poor cardiorespiratory reserve, RF ablation alone or followed by conventional radiation therapy with or without chemotherapy may prove to be a treatment option. In patients with metastatic disease, RF ablation may be suitable for treatment of a small tumor burden or for palliation of larger tumors that cause symptoms such as cough, hemoptysis, or pain. Patients with chest wall or osseous metastatic tumors in whom other therapies have failed may benefit from RF ablation as an alternative to radiation therapy.

Improvement of tumor oxygenation by mild hyperthermia

There is now abundant evidence that oxygenation in rodent, canine and human tumors is improved during and for up to 1-2 days after heating at mild temperatures. An increase in tumor blood perfusion along with a decline in the oxygen consumption rate appears to account for the improvement of tumor oxygenation by mild hyperthermia. The magnitude of the increase in tumor pO(2), determined with oxygen-sensitive microelectrodes, caused by mild hyperthermia is less than that caused by carbogen breathing. However, mild hyperthermia is far more effective than carbogen breathing in increasing the radiation response of experimental tumors, probably because mild hyperthermia oxygenates both (diffusion-limited) chronically hypoxic and (perfusion-limited) acutely hypoxic cells, whereas carbogen breathing oxygenates only the chronically hypoxic cells. Mild hyperthermia is also more effective than nicotinamide, which is known to oxygenate acutely hypoxic cells, in enhancing the radiation response of experimental tumors. The combination of mild hyperthermia with carbogen or nicotinamide is highly effective in reducing the hypoxic cell fraction in tumors and increasing the radiation response of experimental tumors. A primary rationale for the use of hyperthermia in combination with radiotherapy has been that hyperthermia is equally cytotoxic toward fully oxygenated and hypoxic cells and that it directly sensitizes both fully oxygenated and hypoxic cells to radiation. Such cytotoxicity and such a radiosensitizing effect may be expected to be significant when the tumor temperature is elevated to at least 42-43 degrees C. Unfortunately, it is often impossible to uniformly raise the temperature of human tumors to this level using the hyperthermia devices currently available. However, it is relatively easy to raise the temperature of human tumors into the range of 39-42 degrees C, which is a temperature that can improve tumor oxygenation for up to 1-2 days. The potential usefulness of mild hyperthermia to enhance the response of human tumors to radiotherapy by improving tumor oxygenation merits continued investigation.

Predictive factors in radiotherapy for non-small cell lung cancer: present status

PURPOSE

To evaluate the predictive factors for radiation response in non-small cell lung cancer (NSCLC) and the role of such factors in guiding high dose radiation therapy.

METHODS

The first International Workshop on Prognostic and Predictive Factors in Lung Cancer was organized by the Hellenic Cooperative Oncology Group and held in Athens, Greece under the auspices of the International Association for the Study of Lung Cancer. Presentations at this meeting provided the outline of this report, which has also been supplemented with available data from the current literature.

RESULTS

The predictive factors for both the natural history and the therapy outcome of NSCLC are grouped as follows: (1) tumor related factors (anatomic factors); the extent of tumor (tumor stage) is one of most important prognostic factors affecting the therapy outcome. Tumor size (T stage), anatomical structures involved (T4 vs. T3 lesion), and the presence of regional lymph node metastasis have a significant impact on both prognosis and response to appropriate therapy; (2) host-related factors (clinical factors) that are important in therapy response include performance status, weight loss of more than 10% of body weight in the previous 6 months, and associated co-morbidities, i.e. pulmonary and cardiac diseases; (3) technical factors of radiation therapy which play a decisive role in successful outcome. The target volume should be defined accurately using modern imaging studies. The radiation dose fractionation schedule, in terms of the dose intensity and total dose, should be high enough to provide local tumor control in the majority of patients. Three-dimensional (3-D) conformal planning is an essential tool in dose escalation studies to determine the maximum tolerated dose of radiation; (4) biological/radiobiological/metabolic factors. Biologic markers resulting from genetic lesions in lung cancer are grouped as follows: (a) oncogene amplification and overexpression (aberrant gene expression) and mutated tumor suppressor genes -- ras gene, myc gene, HER-2/neu and survivin gene, p53 and mutated beta-tubulin gene; (b) tumor biologic/radiobiologic factors -- tumor cell proliferation kinetics, hypoxia, intrinsic cellular radiosensitivity, gamma factor, and DNA content; (c) enzymes and hormones: neuron-specific enolase, serum lactate dehydrogenase, and enhanced glucose metabolic rate supported by increased glucose transporter protein. The surviving fraction of tumor cells at 2.0 Gy of radiation (SF2) as a measure of intrinsic tumor cell radiosensitivity, potential doubling time (T(Pot)) as a measure of the rate of tumor cell proliferation and gamma factor representing the slope of the survival curve at 50% survival rate are being investigated as potential predictors for therapy response. Enhanced glucose utilization, a hallmark of malignant transformation, is being studied as a potential monitor for therapy response by using PET-FDG.

CONCLUSION

Current data indicate that there is a dose-response relationship between radiation dose and local tumor control, and also between local tumor control and survival in stage III NSCLC. Therapeutic factors, i.e. total radiation dose, fractionation schedule and dose intensity, and use of 3-D conformal radiation to secure the optimum therapeutic ratio are important for improved local tumor control and survival. Future research should be directed towards radiation dose escalation using 3-D conformal therapy to determine the maximum tolerated dose (MTD) of radiation in chemo-radiotherapy, and the use of this MTD for improved local tumor control and survival. Radiobiological, molecular, and metabolic markers may have potential for monitoring tumor response and optimizing radiation therapy.

New technique for mediastinal temperature measurement in hyperthermic cancer treatment: balloon catheter in the azygos vein

The temperature in the mediastinum during hyperthermia is difficult to determine accurately. We measured the temperature in the azygos vein, using a new technique, and compared the measurements with temperatures in the oesophagus. Eight patients with mediastinal tumours resulting from lung cancer or oesophageal cancer were given hyperthermo-radiotherapy. The temperatures in the azygos vein and in the oesophagus were measured before and during blockage of the blood flow of the azygos vein using an angiographic balloon catheter. None of the patients had complications as a result of these procedures, and hyperthermia by capacitative heating was safely performed. The temperature in the azygos vein increased by a mean of 1.7 degrees C (0.2-2.8 degrees C) after blockage of the blood flow. The temperature in the oesophagus was 0.83 +/- 1.09 degrees C (mean +/- SD) higher than that in the azygos vein. Measurement of the temperature in the azygos vein gives a more accurate estimate of mediastinal temperature than does oesophageal temperature but it is an invasive procedure.

Clinical experience using 8 MHz radiofrequency capacitive hyperthermia in combination with radiotherapy: results of a phase I/II study

PURPOSE

Since 1985, the University of Minnesota Hospital and Clinic has investigated the efficacy and safety of 8 MHz radiofrequency (RF) capacitive hyperthermia using the Thermotron RF-8. This study reports the thermometric and clinical results of 119 patients treated with RF hyperthermia in combination with radiotherapy (RT).

METHODS AND MATERIALS

Of 119 patients, 69 received high-dose RT and 50 patients received low-dose RT because of previous irradiation to the treatment site. The most common anatomic sites treated were within the pelvic cavity or head and neck area. Thirty-three percent and 24% of tumors treated were > 7 cm and > 10 cm in largest diameter, respectively. Forty percent of the patients had deep-seated tumors (depth > 6 cm). Hyperthermia was given as soon as possible after RT twice weekly, allowing at least 72 h between treatments. The objective was to raise intratumoral temperatures to 42-43 degrees C or above for 30-50 min while keeping normal tissue temperatures below 40-41 degrees C.

RESULTS

Of 119 patients, 40% achieved a Tmax tumor temperature of > 42 degrees C and 40% achieved 40-42 degrees C Tmax. Higher Tmax) tumor temperatures were observed as tumor size increased. Tumors > 10 cm in largest diameter had a Tmax of 42.2 degrees C. Tumor depth was not a significant factor for the tumor temperatures achieved. Of 119 patients, 11% achieved complete response and 38% achieved partial response. Of the no-response patients, 34% had symptomatic palliation and 15% had stable disease for at least 12 months after treatment. We were able to treat tumors of patients with subcutaneous fat as thick as 3 cm by precooling the fat for 20 min with 10-15 degrees C saline-filled boluses prior to the initiation of heating. During treatment, 60% of patients complained of varying degrees of pain and 19% had pain that was a factor in limiting treatment. Vital signs were relatively stable and not a factor in limiting treatment.

CONCLUSION

The Thermotron RF-8 is a useful hyperthermia device that can raise tumor temperatures to a therapeutic level (i.e., 42 degrees C) in a significant proportion of patients with superficial, subsurface, and deep-seated tumors, with minimal adverse effects, complications, and systemic stress. Further clinical studies using improved thermometry systems are warranted.

Present and future status of noninvasive selective deep heating using RF in hyperthermia

To achieve hyperthermia using electromagnetic energy, RF of under 100 MHz is basically suitable for the external heating of the deep portions of the body. For applicators using such RF, the following types are considered: capacitive, inductive, radiative and hybrid. With radiative applicators, the intensity of the EM waves radiated from the applicator decreases with propagation into the material to be heated, but the phased annular array of radiative applicators potentially increases the intensity of the EM energy in the deep portion owing to the interference of the waves. Using this method, the focusing of EM energy depends on the dielectric properties of the material to be heated. With respect to RF heating at a lower frequency than the RF used for the annular phased array, some devices have been said to concentrate EM energy in the deep portions, where the characteristics of 'wave' are not utilised. To this end, some methods using capacitive electrodes, an inductive coil, or a combination of both, are being designed. The results of using such methods have shown that it is possible to supply sufficient EM energy to the muscle layers deep in the material to be heated, without heating the fat layers excessively.

Temperature-dependent ultrasound color flow Doppler imaging in the study of a VX2 tumor in rabbits: preliminary findings

Neovascularity in a VX2 carcinoma in rabbit liver was detectable, using an ultrasonic color Doppler flow imager. Intraportal infusion of heated saline increased the fractional area of color flow Doppler signals by at least 5% and as much as 30%, within and surrounding the tumors of all six rabbits studied. The effect of the fluid load was an increase in fractional area of color flow Doppler signals by 5 to 20% and was determined by the measurements following infusion and return to baseline temperature. The largest increment in color Doppler signal was observed in peritumoral vessels (10-40%). In contrast, the fractional area of color-coded pixels within the tumor was only slightly higher or lower (5-10%) at the peak temperature than at the baseline measurements. The temperature within the tumors was as much as 1 degree lower than parenchymal tissue in all animals measured. This was presumably due to the portal vein blood supply to normal tissue and predominantly hepatic artery supply to the pathological tissue. High velocities and persistent bidirectional flow were observed within the tumors only at the peak temperatures (> 43.5 degrees C). This experiment suggests that thermal stress may enhance tumor detectability by color Doppler imaging. Further development of a quantitative analysis method for color Doppler studies is needed.

Evaluation of CT images, tumour response and prognosis after thermoradiotherapy for deep-seated tumours

Thermoradiotherapy was applied for the treatment of deep-seated tumours in 41 patients. Low-density area (LDA) on CT images which appeared or expanded within the tumour after treatment was evaluated. Derived conclusions are as follows: (1) of 41 patients, LDA newly appeared or expanded in 24; (2) change of density was related closely with size of a tumour, histological characteristics of the tumour and heating condition; (3) histologically, LDA consisted of coagulation necrosis and tumour cells at the peripheral wall were highly degenerated; (4) a greater extent of LDA indicated the increasing possibility of local control; (5) probability of survival for patients with an increase of LDA was significantly superior to those without changes of LDA; (6) LDA may be a good landmark for judgement of the prognosis of a patient treated by thermoradiotherapy; and (7) new criteria of treatment effectiveness including density changes were proposed.

Precooling prevents overheating of subcutaneous fat in the use of RF capacitive heating

The usefulness of precooling subcutaneous tissue in the hyperthermic treatment of deep-seated human tumors with capacitive application of radio-frequency (RF) was investigated. A capacitive hyperthermia unit operated at 8 MHz of radiofrequency was used to heat deep-seated human tumors. The electrode surfaces were covered with flexible vinyl sheets and the space between the electrode and the vinyl sheets perfused with 0.4% saline. The temperature of the saline was controlled by circulating the saline through built-in heat exchangers. The depth of heating was controlled by pairing electrodes of different diameters. When subcutaneous fat was less than 1 cm thick, various deep-seated tumors could be heated to a therapeutic temperature without significant discomfort in the subcutaneous tissue as long as the skin was properly cooled with the cold saline bolus. However, the same cooling method could not prevent the occurrence of pain in subcutaneous tissue in obese patients. The pain usually developed when the temperature of subcutaneous fat 1-2 cm below the skin surface exceeded 42 degrees C. We observed that cooling the human skin surface with 10 degrees C bolus for 20 min could substantially lower the temperature of fat as deep as 2.0-2.5 cm. Therefore, when the subcutaneous tissue was precooled with 10 degrees C saline for 20 min or longer before heating, it was possible to prevent successfully the overheating of subcutaneous fat as thick as 2.0-2.5 cm and to raise the temperature of deep-seated tumors to therapeutic levels.

Interstitial hyperthermia of malignant brain tumors by implant heating system: clinical experience

An implant heating system using a ferromagnetic implant with low Curie temperature has been developed for treating human brain tumors. Safe and repeated hyperthermia was possible over periods averaging ten weeks in 23 out of 25 patients with malignant brain tumors without development of major side effects. Evaluation of the effects of this new treatment is still preliminary. Overall response rate was 34.8%. However, five of thirteen cases of malignant glioma and two of five cases of brain metastasis were responded well to interstitial hyperthermia given with or without irradiation. Pathological findings common to the treated tumors were circumscribed, ellipsoid shape of coagulation necrosis around the implant. Degeneration of tumor cells, hemorrhage, vascular stasis and thrombosis were found adjacent to the necrosis. In the future, a combination of interstitial hyperthermia with brachytherapy and chemotherapy may offer improved local control of brain tumor.

The effects of fractionated hyperthermia on normal canine muscle blood flow

This study investigates the changes in normal canine muscle blood flow occurring during three fractions of 43 degrees C (60 min) hyperthermia. Blood flow was measured during heating at 1-, 3-, and 5-day intervals with a laser Doppler flowmeter. For 1-day intervals, blood flow oscillated during the first treatment reaching peak values of approximately 39 ml/min per 100 g of tissue after 8 min and 47 ml/min per 100 g of tissue after 40 min. Heatings at 1-day intervals showed both peaks in perfusion to persist during subsequent treatments with higher blood flows during later heatings. Results of the 3-day fractionated heating demonstrated lower blood flows during the second and third heatings than those at 1-day intervals. The third treatment of the 3-day fractionations showed a disappearance of the first peak and only a small increase in perfusion at the second peak (50 ml/min per 100 g of tissue). Perfusion studies at 5-day intervals demonstrated two peaks at approximately 15 and 40 min. Compared with the first treatment at 5-day intervals, the second and third treatments demonstrated decreased and increased peak perfusion values, respectively. This study suggests that the kinetics of blood flow changes during hyperthermia may be the result of several different mechanisms. There appear to be three different peaks which can be quantified during heating. These peaks may change during subsequent heating independently from one another. Further work must be performed to examine the physiological mechanisms responsible for each peak.

Histopathological changes of human tumors following thermoradiotherapy

Twenty human malignant tumors treated with thermoradiotherapy were examined histopathologically. Hyperthermia was administered regionally with a 13.56-MHz or 8-MHz RF heating device, once or twice a week after irradiation, 2 to 12 sessions in total. Fifteen tumors received a total radiation dose of 26 to 70 Gy in fractions of 1.8 Gy to 2.0 Gy a day, 5 days a week, whereas five tumors received a total dose of 20 to 60 Gy in fractions of 4 Gy each, twice a week. Microscopic examination of 4 of the 20 tumors revealed complete necrosis throughout the cross-section of the entire tumor. All the four tumors had received a total dose of over 60 Gy and a tumor center temperature of over 42 degrees C. In 10 tumors, more than 50% but less than 99% of the cross-section of the entire tumor had massive coagulation necrosis. The remaining six tumors showed relatively little change; the area of intratumor necrosis was less than 50%. The grade of tumor necrosis was dependent on both the temperatures of tumor center and periphery, and a total radiation dose. The small blood vessels and capillaries in the tumor parenchyma were markedly damaged in 16 of the 20 tumors, while the blood vessels in the tumor stroma were damaged in only 2 tumors. Condensation of the destroyed nucleus observed in 15 tumors was considered to be a typical change induced by thermoradiotherapy. Viable tumor cells remained in the tumor central area in only four tumors and around the blood vessels in only three tumors. However, in the tumor peripheral area, viable tumor cells were observed in 16 out of the 20 tumors. These results indicate that histopathological changes induced by thermoradiotherapy are greater in the tumor central area than in the tumor peripheral area, and provide strong rationale for utilizing full dose radiation therapy in combination with hyperthermia as opposed to lower doses for cancer therapy.

Morphologic and morphometric studies on tumor necrosis produced by radiotherapy, and hyperthermia singly and in combination

The purpose of the present study was to evaluate the therapeutic effects of hyperthermia associated with radiotherapy on neoplasia. Two transplanted experimental tumors (undifferentiated carcinoma of mouse breast and sarcoma 37) were used. A protocol was followed that included, for both models, four groups of animals: 1) control group; 2) radiotherapy group; 3) hyperthermia group; 4) radiotherapy associated with hyperthermia group. The animals were sacrificed after therapy according to a different schedule for each type of tumor. The morphology of the neoplasia in every group of treated tumors was compared with that of the control group. For quantitative evaluation of the necrosis, we studied the ratio of the tumor necrotic areas (N) to a tumor standard area (T). From the results obtained, the following conclusions were made: 1) Necrosis produced by combined treatment was significantly greater than that obtained by using one only; 2) necrosis appeared early after treatment and remained relatively unchanged; 3) The damaging effect of the hyperthermia occurred earlier than that produced by radiotherapy when these methods were used separately, thus suggesting distinct mechanisms of tumor necrosis.

Radiofrequency hyperthermia therapy of murine melanoma: a comparison of fractionated versus single-dose treatments

The effects of single and fractionated doses of radiofrequency hyperthermia were investigated in the treatment of cutaneous murine melanoma. S91 murine melanoma cells were implanted into preformed intradermal blister cavities on the backs of DBA/2J mice. Evaluation of treatment response was undertaken after single and fractionated doses of hyperthermia. A single 60-second treatment at 46 degrees C did not result in any complete regressions, while 3 weekly 46 degrees C treatments produced a 40% incidence of tumor regression. Higher temperature therapy was associated with improved cure rates. A single treatment for 60 seconds at 50 degrees C resulted in a 25% complete response rate while 3 weekly 50 degrees C treatments resulted in the eradication of 92% of the treated tumors. In those tumors that responded only partially to hyperthermia, fractionated low- (46 degrees C) and (50 degrees C) high-dose regimens resulted in significantly smaller melanomas than single-treatment schedules at the same temperatures. It is concluded that fractionated hyperthermia is an effective modality in the control of intracutaneous murine melanoma. If other cutaneous malignancies are also sensitive to heat, this may provide a useful nonsurgical means of treating skin cancer.

Evaluation of ring capacitor plates for regional deep heating

Based upon a capacitive system a quasi-microwave cavity operating at a frequency of 13.56 or 27.12 MHz has been developed. The prototype consisted of two capacitive plates with a circular aperture at the centre of each plate in which a cylindrically shaped tissue volume can be placed. Phantom measurements showed that a second-generation applicator, consisting of two narrow rings with equal inner and outer diameter, gave identical results. Due to the positioning of the rings along the enclosed tissue cylinder, the electrical field is mainly parallel to the body axis. SAR distributions were measured by infrared thermography in cylindrical, muscle equivalent phantoms enclosed in PVC-tubes using the 'split phantom' technique. For phantom diameters up to 13.5 cm a homogeneous heating, SAR 70-100 per cent of the maximum SAR, has been obtained over the tissue volume between the inner edges of the two rings. For these measurements the non-isolated ring electrodes are placed directly onto the PVC cover. When the phantom diameter, excluding PVC cover, is increased to 22.5 cm the SAR values at the centre vary from 30 to 40 per cent of the maximum SAR value which is located near the inner edge of the rings. In this case a 1 cm gap between the rings and the PVC cover was used in order to reduce the intensity of the hot spots. In all experiments no cooling of the phantom surface or ring electrodes has been used. The results from this initiating study indicate the feasibility of this type of applicator for regional deep heating, although more experimental work is needed when the applicator is used to heat tissue bodies with a diameter larger than 13.5 cm. Already, the applicator in its most simple design may be of clinical value for hyperthermic treatment of tumors in arms or legs.

Capacitive radiofrequency hyperthermia in the treatment of cutaneous murine melanoma

We have evaluated localized capacitive radiofrequency hyperthermia in the treatment of murine S91 melanoma. Two hundred and ten DBA/2J male mice were implanted with 1 X 10(6) S91 murine melanoma cells innoculated into a noninflammatory upper dermal suction blister cavity. Two tumors were implanted per animal, so that each animal served as its own control in evaluating the effects of temperature, treatment duration, and tumor size on tumor growth following radiofrequency hyperthermia treatment. The data supported the following conclusions: (1) capacitive radiofrequency hyperthermia is effective in the treatment of murine S91 melanoma; (2) duration of treatment between 10 and 60 seconds at 52 degrees C does not influence effectiveness; and (3) treatment temperatures greater than 49 degrees C are needed for maximal effectiveness in the treatment of these tumors. Based on these preliminary findings, high temperature, short duration capacitive radiofrequency hyperthermia may prove to be a useful modality in the treatment of certain cutaneous malignancies.

Effect of multiple heatings on the blood flow in RIF-1 tumours, skin and muscle of C3H mice

The effect of one to five multiple heatings on blood flow in the RIF-1 tumour, skin and muscle of C3H mice was studied. When heated for 1 h at 43.5 degrees C the tumour blood flow increased 1.8 times, and rapidly decreased after the heating to less than half the control value. The 2nd-5th heatings at 43.5 degrees C, applied at 1- or 3-day intervals, caused no further significant change in the tumour blood flow. In the skin and muscle the blood flow increased 5 times when heated for 1 h at 43.5 degrees C, and remained at 1.5-2.0 times of control for 1-3 days after the heating. The blood flow in the skin and muscle, particularly in the skin, was further increased by the 2nd-5th heatings applied at 3-day intervals, but not at 1-day intervals, albeit the additional increase was very small. Consequently, whereas the tumour blood flow was 5-6 times greater than that in the skin and muscle before heating, it was only about 1.5-2.0 times greater than that in the skin and muscle during the 1st heating. The tumour blood flow became more or less similar to the normal tissue blood flow during the 2nd-5th heatings given at 3-day intervals. The decline in the vascular response in normal and tumour tissues to the 2nd-5th heatings suggested development of vascular thermotolerance.

Multi-institutional studies on hyperthermia using an 8-MHz radiofrequency capacitive heating device (Thermotron RF-8) in combination with radiation for cancer therapy

A joint clinical trial of hyperthermia using a newly developed 8-MHz radiofrequency (RF) capacitive heating device (Thermotron RF-8; developed in cooperation with Yamamoto Vinyter Co. of Osaka) was performed under collaboration of seven institutions. Radiation with 4 Gy twice a week for a total of 40 Gy or 2 Gy five times a week for a total of 50 Gy was delivered. After irradiation, hyperthermia at 42.5 degrees C +/- 0.5 degree C for 40 to 60 minutes was given twice a week for a total of 10 times. Tumors examined in this trial were located in various depths in the body, and included those which were considered refractory to conventional treatments or radioresistant such as malignant melanoma and soft tissue tumors. Of the 63 tumors treated, 52.4% showed complete regression (CR); 19.0% more than 80% regression (PRa); 20.6%, 80% to 50% regression (PRb); and 8.0% no regression (NR). Our joint clinical trial demonstrated that hyperthermia with the use of the Thermotron RF-8 is safe and effective in the treatment of radioresistant tumors located in superficial, subsurface, and in some cases deep regions, if the surface cooling is properly managed by the temperature-controlled saline pad and electrodes of appropriate size are paired.

Capacitive heating of phantom and human tumors with an 8 MHz radiofrequency applicator (Thermotron RF-8)

The thermal profile was investigated in agar phantoms and in human tumors heated capacitively with 8 MHz RF. Deep and homogeneous heating could be achieved in a large homogeneous phantom of 25 cm diameter and 24 cm thick when heated with a pair of 25 cm diameter electrodes, coupled to both bases of the phantom. When the size of the two electrodes was not the same, the region near the smaller electrode was preferentially heated. It was, therefore, possible to control the depth of heating by choosing properly sized electrodes. Therapeutic temperature (greater than 42 degrees C) could be obtained in 7 out of 9 small, as well as, bulky superficial human tumors as large as 8 X 8 X 10 cm. Indications are that heating of some deep-seated human tumors might be achieved by the capacitive method, provided that subcutaneous fat layer is cooled by temperature controlled bolus and large electrodes are used. The effect of the anatomical structure on the power deposition in the human body during capacitive heating should be further investigated.

Histopathological observations in the canine prostate treated by local microwave hyperthermia

A large series of repeated experiments were performed applying localized microwave hyperthermia to the prostate in dogs using a new water-cooled skirt-type antenna [1], operating at 915 MHz, as part of a new hyperthermia apparatus being developed for the treatment of the prostate in humans. The prostate gland of 20 male dogs was heated repeatedly under general anesthesia, at temperatures between 40 degrees C and 47 degrees C, and for different lengths of time up to 10 h. The prostate and other tissues were evaluated histopathologically following treatments. Invariably, all treatments by hyperthermia of the prostate caused a mononuclear inflammatory infiltration in the interstitium and polymorphonuclear infiltration in the glandular elements. Permanent tissue damage was found to be time-and temperature-dependent. Heating at 42.5 degrees C (+/- 0.5 degrees 5C) for up to 1.5 h was found to be harmless and could be safely repeated with our equipment. This study was part of a preclinical evaluation of a new antenna and apparatus.

Hyperthermia-induced vascular injury in normal and neoplastic tissue

The sequential morphologic alterations in normal skeletal muscle in rats, Walker 256 tumors in rats, and transmissible venereal tumors (TVT) in dogs following microwave-induced hyperthermia (43 degrees C and 45 degrees C for 20 minutes), were studied by histologic and ultrastructural examination. Normal muscle and Walker 256 tumors showed edema, congestion, and hemorrhage at 5 minutes post-heating (PH), followed by suppuration, macrophage infiltration, and thrombosis at 6 and 48 hours PH, and finally by regeneration and repair by 7 days PH. Vascular endothelial damage and parenchymal degeneration were present 5 minutes PH. Progressive injury occurred for at least 48 hours PH. Two hyperthermia treatments separated by a 30- or 60-min cooling interval, were applied to Walker 256 tumors in a subsequent study. Increased selective heating of tumor tissue versus surrounding normal tissue, and increased intratumoral steady state temperatures were found during the second hyperthermia treatment. Canine TVTs were resistant to hyperthermia damage. These results suggest that vascular damage contributes to the immediate and latent cytotoxic effects of hyperthermia in normal tissue and some types of neoplastic tissue, and that selective heating of neoplastic tissue occurs in tumor tissue with disrupted microvasculature.

Hyperthermia-induced vascular injury in normal and neoplastic tissue

The sequential morphologic alterations in normal skeletal muscle in rats, Walker 256 tumors in rats, and transmissible venereal tumors (TVT) in dogs following microwave-induced hyperthermia (43 degrees C and 45 degrees C for 20 minutes), were studied by histologic and ultrastructural examination. Normal muscle and Walker 256 tumors showed edema, congestion, and hemorrhage at 5 minutes post-heating (PH), followed by suppuration, macrophage infiltration, and thrombosis at 6 and 48 hours PH, and finally by regeneration and repair by 7 days PH. Vascular endothelial damage and parenchymal degeneration were present 5 minutes PH. Progressive injury occurred for at least 48 hours PH. Two hyperthermia treatments separated by a 30- or 60-min cooling interval, were applied to Walker 256 tumors in a subsequent study. Increased selective heating of tumor tissue versus surrounding normal tissue, and increased intratumoral steady state temperatures were found during the second hyperthermia treatment. Canine TVTs were resistant to hyperthermia damage. These results suggest that vascular damage contributes to the immediate and latent cytotoxic effects of hyperthermia in normal tissue and some types of neoplastic tissue, and that selective heating of neoplastic tissue occurs in tumor tissue with disrupted microvasculature.

Hyperthermia and radiation in vivo: effect of 2-deoxy-D-glucose

Since hypoxic cells rely heavily on glucose metabolism for energy, 2-deoxy-D-glucose (2-DG), an inhibitor of anaerobic glycolysis, would be expected to increase tumor cell killing by heat and thus enhance the effect of concurrent radiation. In order to test this hypothesis two types of BALB/c mouse tumors, one induced by subcutaneous injection of 10(6) herpes virus Type 2-transformed (H238) cells and the other by injection of 1.6 X 10(5) 1,2-dimethylhydrazine-transformed (#51) cells in the right thigh, were subjected to radiation, 2-DG, and heat used singly and in various combinations. Control mice were injected with saline. Three to four weeks after inoculation the mice were assigned to one of eight treatment groups (28 mice/group) so that average tumor volume/group before treatment would be equivalent. A single 2000 rad dose of radiation 3 hr prior to heat and 2-DG injected intraperitoneally at 1 g/kg 30 min before heating were given to some of the groups. Localized heat at 43.5 +/- 0.1 degrees C for 30 min, when used, was administered by means of a water bath. Rectal temperatures were kept below 39 degrees C, whereas intratumor temperatures reached a maximum of 42 degrees C. After treatment, tumor volume, mouse weight, and mortality were noted twice a week for four weeks. In both tumor models, mice receiving radiation plus heat, and radiation plus heat plus 2-DG, had significantly smaller tumors over the entire 4 to 28 day range after treatment than saline-injected control mice. In addition, in the H238 tumor model, addition of 2-DG to treatment with radiation and heat resulted in significantly smaller tumors at 25 days. 2-DG alone or in combination with heat (without radiation) resulted in significantly smaller H238 cell-induced tumors at day 28 post-treatment when compared to the saline controls. The H238 tumor-bearing mice experienced a significant (4.7%) loss in total body weight after heating. It could be that heating trauma produced dehydration and possibly also decreased caloric intake to an extent which could be measured in weight loss. This observation, however, was not made in the heated mice in the #51 tumor model.

Deep-heating characteristics of an RF capacitive heating device

An RF capacitive heating device was constructed and its deep-heating characteristics were studied using three mini-pigs. The deep-heating ability of RF capacitive heating was found to be improved by enlarging the electrodes, driving at 8 MHz, cooling the skin under the electrodes, inserting a bolus between the body and the electrodes and considering the anatomical structure of the body. The heating characteristics obtained were as follows. When applicators were placed on both sides of the abdomen of a mini-pig, 7 mm in fat layer thickness and 23 cm in lateral chest thickness, the increase in temperature of the deep part was greater than that of the fat layer. When applicators were placed on the posterior and anterior abdomen, overheating was noted in the fat and muscle near the back. The temperature was highest in a mock tumour, made by blocking blood flow to the spleen. The bio-heat equation revealed that RF capacitive heating accompanied by surface cooling at 10 degrees C could heat the deep portion of the body to 42 degrees C without excessive heating of a 1.6 cm thick fat layer.

Integration of allogeneic lymphocyte immunotherapy with short-course chemotherapy and hypoenergic hyperthermia: a "triple-threat" treatment for disseminated cancer

A strategy for treatment of disseminated cancer is proposed which unites short-course chemotherapy, local hyperthermia, and allogeneic lymphocyte immunotherapy, designed and timed so as to optimize their synergistic interactions. Short-course chemotherapy potentiates allogeneic lymphocyte immunotherapy, and in turn is potentiated by subsequent courses of local hyperthermia. Response to hyperthermia can be enhanced by measures which selectively inhibit tumor blood flow, impair tumor energy metabolism, and produce tumor acidification; these include induction of prolonged hyperglycemia, and administration of selectively activated "hypoenergic" agents which inhibit or uncouple tumor respiration. It is anticipated that these methods will enable a significant advance in the control of metastasized solid tumors.

Hyperthermia for cancer: a practical perspective

A causal relationship between hyperpyrexia and tumor regression was first suggested in 1866, when Busch reported the cure of a histologically diagnosed sarcoma in a middle-aged woman, following a bout of erysipelas. Over the years, interest in the effect of heat on cancer has remained alive, but this interest has increased dramatically in recent years. The literature on this subject is broadly reviewed and the clinical results discussed. It is apparent from clinical studies thus far that it is a relatively simple undertaking to treat superficial neoplasms with hyperthermia. However, the major challenges in clinical thermotherapy pertain to patients with deeply situated tumors. The lack of safe and reliable methods of monitoring temperature in deep tissues is a major impediment to a thorough understanding of thermal dosimetry in clinical hyperthermia, and routine thermal dosimetry in clinical hyperthermia will have to await the development of reliable noninvasive thermometry. As responses have been reported with modest levels of hyperthermia, the need for thermometry is somewhat lessened, given that invasive monitoring is imperfect and somewhat risky when used in deeply seated tumours. The eventual place of thermotherapy in the treatment of malignant tumours in man is as yet unclear and must be rigourously and thoroughly assessed in well-designed, prospective, randomized patient trials.

Blood flow and intravascular volume of mammary adenocarcinoma 13726A and normal tissues of rat during and following hyperthermia

The effects of hyperthermia on blood flow and intravascular volume were studied in mammary adenocarcinoma 13762A growing subcutaneously in the leg of Fischer F344 rats. The blood flow was determined using microspheres labelled with 125I, and the blood volume was determined using red blood cells labelled with 51Cr. At the end of heating with water bath at 43.5 degrees C for 1 hour, there was a marked elevation of 51Cr in tumor. The 125I content in tumor also was mildly elevated. Histologically there was a greater number of patent blood vessels per unit area, and they were dilated and hyperemic. In addition, widespread and diffuse hemorrhage could be seen. It appeared, therefore, that the increased 51Cr and 125I label in the tumors immediately after heating was, at least in part, a result of leakage of the labels to extravascular space in addition to possible vasodilation and increased blood flow. At 1 and 5 hours after heating, tumor blood flow was considerably reduced, and at 16 hours both tumor blood flow and blood volume were considerably reduced. Histological examination demonstrated that the tumor blood vessels remained dilated and hyperemic after heating. The effect of heat on blood flow and blood volume in the skin and muscle adjacent to the tumors was also investigated. Blood flow and blood volume in the surrounding normal tissues were significantly elevated at the end of heating. Blood flow was relatively unchanged at 1, 5, and 16 hours after heating, but blood volume was reduced to about one half. These findings indicate that hyperthermia may induce greater damage to vasculature of tumors than normal tissues, and that vascular damage in tumors may take some time to express itself following moderate hyperthermia.

Radiofrequency-induced hyperthermia: computer simulation of specific absorption rate distributions using realistic anatomical models

A description is given of a computer simulation technique which predicts the specific absorption rate (SAR) distribution within the human body resulting from the application of radiofrequency electromagnetic energy. The method uses an extension to the principle of over-relaxation of electric potentials and the basis of the simulation is a realistic three-dimensional model derived from both dielectric and anatomical data. Two of the principal means of applying radiofrequency hyperthermia, namely the use of capacitive electrodes and inductive coils, have been provided for. The accuracy of the simulation has been favourably tested using an agar split-phantom and an infrared thermograph camera. The simulations can be used to assist the design and clinical use of radiofrequency applicators, and examples are given of the application of both an inductive coil and switched capacitive electrodes to heat the thorax.

Effect of hyperthermia, radiation and adriamycin combinations on tumor vascular function

Pathophysiologic studies of tumor vascular responses to hyperthermia, radiation or adriamycin given alone or in specific combinations have been made in the cervical carcinoma grown in the transparent cheek pouch chamber of the Syrian hamster. A specially designed chamber containing a compartment for flowing water enabled controlled heating of the tumor and pouch to within 0.2 degrees C; the desired temperatures were achieved within one minute. Heating at 42 degrees C for 30 minutes was followed, at 1, 5 or 24 hours, by a second heating for 30 minutes at 42 degrees C. In addition, the same period of heating was preceded or followed, at 1, 5 or 24 hour intervals, by a single exposure to 2000R or a single intravenous injection of adriamycin given at a rate of 0.45mg/100gm body weight. Of the three modalities, heat appeared to have the greatest acute effect on the tumor vascular system. A single dose of heat produced a rapid but transient constriction followed by a prominent dilation of vessels. Two heating periods given at a 1 hour interval caused persistent stasis in the tumor which progressed to coagulation necrosis. Although heating prior to irradiation or adriamycin, in general, increased the vascular responses to these agents, this sequence gave no tumor control. Radiation or adriamycin given prior to heating had relatively little effect on the vascular response to heating and produced no tumor control except when heat was applied shortly after irradiation. These studies indicate that changes in the microvasculature and perfusion in tumors, in response to hyperthermia alone or combined in specific sequences with radiation, can alter the internal environment of the tumor to produce a greater degree of tumor control than can be attributed to direct cell killing by these agents.

Sacral chordoma: a case study and review

Chordomas are a low grade, tenacious, but eventually lethal neoplasm for which little improvement in outcome has been reported. A current review of the literature and a case report are provided to support his position. The reported sacral chordoma did respond temporarily to chemotherapy. Its rare occurrence precludes controlled studies of chordoma; therefore, any response merits reporting. The authors observed that hyperthermic chemotherapy was feasible for treating some chordomas but has not yet been reported. It was evaluated for the patient in this report.