Kenichi Kakinuma

Therapeutic efficacy of targeting chemotherapy using local hyperthermia and thermosensitive liposome: evaluation of drug distribution in a rat glioma model

A method was developed of targeting chemotherapy using thermosensitive liposomes to treat malignant gliomas. Using the brain heating system, when the tumour core is heated to >43°C, the tumour infiltrating zone is exposed to mild hyperthermia (40–43°C). Thermosensitive liposomes were designed to release their contents at 40°C to target both the tumour core and tumour infiltrating zone. The present study investigated the anti-tumour effect on rat glioma models in tumour drug uptake and tumour growth delay studies. Elevated accumulation of ADR in the rat C6 glioma after treatment was obtained in the area heated to >40°C. However, there was no significant difference between the areas heated to 40–42°C and >43°C. Furthermore, it was found that ADR concentrations in the mildly hyperthermic areas were significantly higher following treatment with liposomal ADR than with free ADR. The animals treated with the new combination therapy had significantly longer overall survival time in comparison to those receiving other treatments. Thus, thermosensitive liposomes release their contents in response to mild hyperthermia and this combination therapy has a greater therapeutic efficacy for malignant brain tumours. This method is a promising approach for the treatment of malignant glioma patients.

Effects of whole-body hyperthermia on the canine central nervous system

It has been reported that central nervous system (CNS) tissue may be more heat labile than other tissues of the body. However, no definite information has been available on how much heat CNS tissue can tolerate without sustaining damage during whole-body hyperthermia, especially in a chronic stage. In this study, whole-body hyperthermia was induced in dogs by extracorporeal heating of blood, to determine the effects 7 days after hyperthermia on the canine brain and spinal cord. The temperatures of both the brain and the spinal cord were raised to 42.0+/-0.1 degrees C and maintained at that level for 60 min. Seven days later, all of the dogs were sacrificed by transcardial perfusion using 10% formaldehyde phosphate buffer for microscopic examination. The thermal dose resulted in neither microscopic damage to the CNS nor neurological symptoms, as determined by comparison of microscopic and neurological findings with those of dogs whose brain and spinal cord temperatures were maintained at 37.0 degrees C for 60 min. The findings suggest that, for medical purposes, whole-body hyperthermia appears promising for application at a thermal dose of up to 42.0 degrees C for 60 min.

Proliferative potential of recurrent intracranial meningiomas as evaluated by labelling indices of BUdR and Ki-67, and tumour doubling time.

Summary This study was designed to provide the reciprocal relationship among labelling indices of 5-bromodeoxyuridine (BUdR LI), Ki-67 (Ki-LI), and tumour doubling time (Td) of recurrent meningiomas. In our series of 182 primary intracranial meningiomas, 46 cases recurred. The average of BUdR LI and Ki LI for nonrecurrent meningiomas were 0.77±0.13% and 4.71±1.96%, respectively. Recurrent meningiomas had significantly higher LIs at the first operation: BUdR LI was 3.77±1.22% and Ki LI was 14.78±3.17%. The recurrent ratio significantly increased with the degrees of each LI. And the linear regression analysis has demonstrated a significant correlation between BUdR and Ki LI. Td was calculated accurately by NIH, a computer software. Td showed a significant inverse correlation with each of the labelling indices. Consequently, BUdR, Ki LIs and Td of individual tumours correlate mutually well. Of the 46 recurrent cases, 4 received radiation after the operation. Td of the irradiated meningiomas tended to be longer than expected for their higher level of BUdR and Ki LIs before radiation therapy. Thus, it was shown that the radiation therapy delays the regrowth of meningiomas.

Planning of hyperthermic treatment for malignant glioma using computer simulation

Interstitial hyperthermia was applied using a radiofrequency generator in the treatment of four malignant glioma patients who had especially deep seated brain tumours or were at high risk. Prior to heating tumours, treatment planning based on an accurate prediction of temperature distribution is essential. The present paper introduces a novel treatment planning method and discusses its clinical efficacy. The two-dimensional finite element method was used for simulation of temperature distribution, which was calculated using the bioheat transfer equation. This technique was applied to plan treatment. Temperature was measured at two points during heating and these values were compared with those estimated by the simulation. In addition, the area of the contrast enhanced (CE) rim on the pre-heating computed tomography (CT) image was compared with the low density area of the CE rim on the post-heating CT image, which was obtained within 2 months after heating. The optimal position and number of radiofrequency (RF) electrodes to include the outside of the CE rim in the simulated area above 42 degrees C contour could be easily determined using this planning system in all cases. The temperature estimated by the simulation was in good agreement with the actual values obtained (within 0.4 degrees C). The post-heating CT image revealed that the hyperthermic procedure described herein achieved more than an 80% low density area within the CE rim in all cases (mean 86.0%). These results demonstrate that this novel treatment planning method may prove to be a clinically valuable tool in the treatment of malignant glioma with RF electrodes.Interstitial hyperthermia was applied using a radiofrequency generator in the treatment of four malignant glioma patients who had especially deep seated brain tumours or were at high risk. Prior to heating tumours, treatment planning based on an accurate prediction of temperature distribution is essential. The present paper introduces a novel treatment planning method and discusses its clinical efficacy. The two-dimensional finite element method was used for simulation of temperature distribution, which was calculated using the bioheat transfer equation. This technique was applied to plan treatment. Temperature was measured at two points during heating and these values were compared with those estimated by the simulation. In addition, the area of the contrast enhanced (CE) rim on the pre-heating computed tomography (CT) image was compared with the low density area of the CE rim on the post-heating CT image, which was obtained within 2 months after heating. The optimal position and number of radiofrequency (RF) electrodes to include the outside of the CE rim in the simulated area above 42°C contour could be easily determined using this planning system in all cases. The temperature estimated by the simulation was in good agreement with the actual values obtained (within 0.4°C). The post-heating CT image revealed that the hyperthermic procedure described herein achieved more than an 80% low density area within the CE rim in all cases (mean 86.0%). These results demonstrate that this novel treatment planning method may prove to be a clinically valuable tool in the treatment of malignant glioma with RF electrodes.

Combination therapy of rat brain tumours using localized interstitial hyperthermia and intra-arterial chemotherapy

Several investigators have reported that a high concentration of drugs in a tumour can be achieved using intra-arterial (IA) chemotherapy. This treatment was highly effective, especially in brain tumours, but the actual therapeutic advantage is still unknown. There are also indications that human malignant gliomas can effectively be treated using interstitial hyperthermia. Therefore, a combined treatment of IA chemotherapy and interstitial hyperthermia should be very promising and this has been studied in a tumour model. Wistar rats with isotransplanted C 6 gliomas in the brain were treated with adriamycin (ADR, 1.0 mg/kg body weight) either infused via the carotid artery (i.a.) or via the tail vein (i.v.), with or without interstitial hyperthermia. Hyperthermia of the tumours was applied using a homemade radiofrequency antenna (RF-heating) and a heating device that maintained the tumour temperature above 40°C. Concentration of adriamycin in tumours after treatment was measured using HPLC. The effectiveness of treatment was determined by the survival time of the animals and histopathological examinations. The highest uptake of adriamycin in the rat C 6 glioma was obtained when the animals were treated with hyperthermia and i.a. ADR infusion ( p <0.01). These animals also showed significantly longer overall survival time (SF50=46 days) in comparison to the other treatments ( p < 0.05). The histological studies demonstrated a necrotic tumour; however, the surrounding normal brain tissue remained intact. Thus, a combination of IA chemotherapy with adriamycin and localized interstitial hyperthermia enhances considerably the efficacy of adriamycin and has a greater antitumour effect for malignant brain tumours. This method is suitable for clinical use, and may be a new strategy for treating gliomas not successfully treated today.

Hyperthermic sensitization by hematoporphyrin on glioma cells

This study investigated: (1) the effect of Hp as a hyperthermic sensitizer on glioma cells; and (2) the possible mechanism of hyperthermic sensitization by Hp using an exogenous scavenger specific to a particular reactive oxygen species. Hp at nontoxic doses at 37 degrees C significantly enhanced thermal cell damage at 41.5 degrees C and above in a dose-dependent manner. Thermal cell damage enhancement by HP was effectively suppressed by the addition of beta-carotene, a singlet oxygen scavenger, or SOD, a superoxide scavenger, but not by the addition of mannitol or catalase. These results support the following hypothesis: The generation of superoxide is increased in cells treated with Hp in combination with hyperthermia. Thermal cell damage enhancement by Hp is probably mediated by singlet oxygen generated via superoxide in an alternative pathway different from that of photosensitization. Hp has potential as a hyperthermic sensitizer because of the following advantages: (1) its dose-dependent enhancement of thermal cell damage; and (2) the lack of toxicity at physiological temperature at doses of Hp required for hyperthermic sensitization of tumour cells.

Chemo-thermotherapy for malignant brain tumor with the combination of thermosensitive liposome and interstitial hyperthermia

Malignant glioma responds poorly to chemotherapy presumably mainly because the antitumor drugs can not be delivered in effective concentrations to the tumor site without causing complications, and because the existence of the blood-brain barrier (BBB) restricts the distribution of many antitumor drugs to malignant gliomas. We used thermosensitive liposomes containing CDDP (cis-diamminedichloroplatinum) with localized heating, and the possibilities of this drug delivery system to the brain tumor were discussed. First, this unique and attractive strategy showed remarkable effects against the RSV-induced subcutaneous tumor which was relatively insensitive to various antitumor agents. The authors then investigated the antitumor effect on rat malignant brain tumor. Ten days after tumor inoculation, six groups were formed : control, free CDDP, hyperthermia, free CDDP+hyperthermia, CDDP-liposome, and CDDP-liposome+hyperthermia. Liposomes containing CDDP (CDDP-liposome) or free CDDP were injected via the tail vein. The brain tumor heating was given using a radiofrequency antenna which was designed at our institute. As a result, the rats treated by CDDP-liposome+hyperthermia had the longest survival time, and the tumor CDDP level of this group was the highest when compared to other groups. These findings suggest that the combination of thermosensitive liposome and localized hyperthermia, could (1) bring a direct thermal killing of the tumor cells, plus (2) increase a permeability of the BBB to transport of CDDP, plus (3) target CDDP-liposomes to the tumor site and produce an effective release of liposomal CDDP with greater activity than when free CDDP was injected.