Regional (deep) heating, clinical studies in progress

Effects of hyperthermia on the peripheral nervous system: a review

The present paper overviews the current knowledge about effects of hyperthermia at temperatures used in clinical oncology on the peripheral nervous system. From the experimental studies it may be concluded that the heat sensitivity of the nerve is determined by the sensitivity of the nerve vasculature. These studies show that in order to avoid induction of severe neuropathy, application of heat to the peripheral nerves should not be in excess of doses of 30 min at 44 degrees C or equivalent. Using modern equipment for application of loco-regional hyperthermia the incidence of even mild neurological complications is very low. In hyperthermic isolated limb perfusion (HILP) neurotoxicity is an often-mentioned side effect, this is in spite of the fact that in all studies a relatively mild hyperthermic temperature is used that, based on the experimental studies, should be well tolerated by the nerves and other normal tissues in the limbs. It seems that the neurotoxicity observed after HILP results from thermal enhancement of drug toxicity, very probably combined with effects of a high tourniquet pressure that is used to isolate the blood flow in the leg. Whole body hyperthermia (WBH), using anesthesia and appropriate monitoring to avoid cardiovascular stress is at present considered a safe procedure. Still in the recent past cases of neuropathy after treatment have been described. When chemotherapy, and notably cisplatin, is administered before or during hyperthermia there are several clinical and experimental observations that indicate a limited tolerance of the peripheral nervous tissue in such case. Also previous radiotherapy may limit the tolerance of nerves to hyperthermia, notably when radiation is applied with a large field size. Experimental studies show that combined treatment with radiation and heat leads to enhancement of effects of radiation (enhancement ratio approximately 1.5 at 60 min at 44 degrees C). A clear contraindication for the application of hyperthermia in patients is the presence of a neurodegenerative disease, such as multiple sclerosis. Vigilance is also required in the treatment of diabetic patients with hyperthermia, this based on experimental animal studies, but so far no clear clinical data are available.

Quality assurance in various radiative hyperthermia systems applying a phantom with LED matrix

The Amsterdam phantom with LED-matrix is applied as an instrument in testing the performance of four types of radiative deep-body hyperthermia systems, which are in clinical use in Germany and The Netherlands. The devices tested were Essen's BSD-1000, Berlin's BSD-2000, Utrecht's Coaxial TEM applicator and Amsterdam's Four-waveguide-array. Photographs were taken of the matrix of dipoles loaded with light-emitting diodes (LED) to visualize the distribution of the RF power deposition or specific absorption rate (SAR) in the aperture midplane. The utility of the phantom with LED matrix for various types of radiative hyperthermia systems is demonstrated. Within this preliminary study, the influence of important parameters on the SAR-pattern in the aperture midplane was demonstrated. After corrections on the phase relation of the applicators a central focus in the SAR distribution could be realized in all systems and could also be moved in any direction. The patterns of the central focus changed in its absolute values and its proportions depending on the relative relations of phase and amplitude of the lateral applicators with respect to the top and bottom applicator. Frequency dependency was recognized for the central focus of the BSD-1000 as well as for the irradiation pattern of a single applicator for the BSD-2000. In the Coaxial TEM applicator it was demonstrated that the dimension of the open water bolus influenced the absolute value of SAR in the aperture midplane.

Phase I/II study, combination of radiotherapy and hyperthermia in patients with deep-seated malignant tumors: report of a pilot study by the Radiation Therapy Oncology Group

This is a report of a Phase I/II study activated in March 1984 and completed in October 1988 by the Radiation Therapy Oncology Group on the feasibility/toxicity of hyperthermia in patients with deep-seated malignant tumors. The main objective of this study was to evaluate the morbidity of regional hyperthermia (systemic and regional, acute and late effects); a secondary objective was to evaluate tumor response to combined irradiation and regional hyperthermia. A total of 54 patients with locally advanced abdominal or pelvic malignancy were accrued to this study; 42% were male and 58% female. Seventy-five of the patients had pelvic tumors and 25% abdominal tumors. Acute toxicities included grade 4 in three patients (1 cutaneous, 1 infection and 1 chemical peritonitis) one grade 3 (skin), and 12 grade 2 toxicities (6 skin and 6 gastrointestinal). With regard to late toxicities, grade 4 was noted in one patient (skin), grade 3 (GI) in one, and grade 2 (skin, peripheral neuropathy) in six patients. The prescribed course of hyperthermia was completed in 17 (32%) of patients. In 36 patients (68%) the course of hyperthermia was terminated, primarily because of patient discomfort. Tumor response was assessed by physical examination or radiological studies. Of 44 patients evaluable for response, there were 17 (39%) complete responses and 6 (14%) partial responders. Significant technical problems in heat delivery and thermometry remain.

Regional hyperthermia--assessment of tolerance to treatment

To assess the patient's tolerance and the complications of treatment associated with delivery of regional hyperthermia using APAS BSD equipment, the data on 30 patients who received regional hyperthermia at the Radiation Oncology Center, Washington University School of Medicine, St. Louis, Missouri, has been reviewed. Most patients presented with advanced or recurrent tumors not amenable to conventional treatment modalities. Hyperthermia was administered in combination with either radiotherapy or chemotherapy. Cardiovascular evaluation was a standard part of pre-treatment work-up. Temperatures were obtained through interstitial probes, catheters inserted into the body cavities and (to record core temperature) esophagus. Local discomfort, anxiety, systemic temperature elevation, and tachycardia were the predominant factors limiting the number of sessions, the duration of sessions and the deposition of power, in 18, 6, 3, and 2 patients, respectively. The complications of treatment were rare. Significant injuries of the superficial tissues were recorded in two patients in whom this could be attributed to contact of urine and stool with the skin surface. Neuropathy was observed in two patients, both of whom had pelvic masses adjacent to or invading into the affected nerves. Both patients had received pelvic irradiation. Neuropathy developed within several days after the first hyperthermia session and proved reversible within several months. No injuries of the visceral organs that could be clearly attributed to hyperthermia have been recorded.

Regional hyperthermia: a feasibility analysis

Thirty patients received regional hyperthermia using the annular phased array system (APAS) in conjunction with either radiotherapy or chemotherapy. A total of 139 treatment sessions were available for analysis, averaging 4.6 per patient. The number of hyperthermia sessions per patient varied from 1 to 9 and was dependent on the patients' tolerance. The duration of the sessions also varied considerably. Although the goal of each session was to attain temperatures of 42 degrees C or higher for 1 h, minimally one-half hour, this was rarely achieved. Temperatures of 42 degrees C or higher were achieved in 95 (68.8 per cent) sessions. The time span at that level ranged between 1 and 40 min, median 8.5 min. The predominant limiting factor in 18 (60 per cent) of patients was local discomfort. Generalized discomfort (anxiety) as a predominantly limiting factor in 5 (16.6 per cent), systemic temperature elevation in 3 (10 per cent), and tachycardia in two (6.6 per cent) patients. Careful attention to technical details and patient preparation may ameliorate or eliminate some of the limiting factors and improve the efficacy of heat delivery.

Heating deep seated eccentrically located tumors with an annular phased array system: a comparative clinical study using two annular array operating configurations

Regional heating administered with an annular array to 12 patients with deep-seated advanced malignant disease eccentrically located in the lower abdomen and pelvis is compared based on the annular array operating configuration. One configuration (4 quadrants active) delivers radiofrequency power with relative uniformity throughout the patient cross-section. The other (2 quadrants active) allows the radiofrequency power deposition to be shifted preferentially into the eccentrically located treatment volume. Phantom measurements have been made to demonstrate the redistribution of radiofrequency power that results when the annular array is operated in these respective configurations. Systemic responses (i.e. oral temperature rise, changes in blood pressure, and heart rate) to these regional hyperthermia applications are compared and are not significantly different with respect to these heating configurations. Temperature data obtained during treatment sessions using these two annular array operating configurations are analyzed based on the fraction of measured tumor and normal tissue temperatures exceeding or equal to a given index temperature. Although the two quadrant configuration is more efficient in delivering power to the treatment volume, this analysis does not indicate a significant gain in therapeutic heating as a result of this preferential power deposition. Treatment tolerance and heterogeneity with respect to tissue type and blood flow remained the dominant limiting factors with regard to temperatures achieved.