Radiofrequency capacitive heating of deep-seated tumours using pre-cooling of the subcutaneous tissues: results on thermometry in Dutch patients.

The capacity of a radiofrequency, 13.56 MHz, capacitive hyperthermia system using extensive pre-cooling of the subcutaneous tissue to induce locoregional deep heating has been investigated in 11 patients. Tumour location was presacral in nine--and eccentric towards the lateral side of the pelvis in two patients. For thermometry multiple catheters (mean 2.7) were inserted into the treatment volume. The mean numbers of temperature measuring points per treatment were 9.4 in tumour, 5.5 in muscle and 7.2 in subcutaneous fat. RF energy was applied after 30 min of cooling through two flexible boli perfused with saline water at 5-10 degrees C. Patient tolerance to pre-cooling was very good and after some initial discomfort the patient became rapidly accustomed to the cold water boli. For some patients better temperatures were achieved when the conventional anterior-posterior applicator set-up was replaced by a set-up with an applicator on each lateral side of the patient. As patients can tolerate temperatures within the fat tissue as high as 45.5 degrees C without complaining it appears important to monitor the temperature at the transition of fat to muscle tissue to prevent subcutaneous burns. The study shows that pre-cooling cannot avoid preferential heating at the interface from fat to muscle tissue. In this patient group the quality of the hyperthermia treatment appeared to be rather poor: 60% of the measured tumour temperatures were below 40 degrees D.     

Use of the vasodilator sodium nitroprusside to increase tumour temperature during loco-regional hyperthermia with a capacitive ring applicator in a rat tumour model

The influence of sodium nitroprusside (SNP) induced hypotension (to a mean arterial pressure of 60mmHg) on tumour and normal tissue temperature during hyperthermia (HT) was examined. Loco-regional HT was given to the calf of BD IX rats by external radiofrequency heating from a capacitive ring applicator. In experiments in rats with subcutaneous BT 4 An tumours, the mean tumour temperature increased by 0.49°C from 42.36 to 42.85°C, on average, during SNP-hypotension. This represented 58% of the increase in tumour temperature found in the same rats when the tumour circulation was stopped completely by sacrificing the rats. SNP-hypotension resulted in a decrease in mean muscle temperature from 41.73 to 41.23°C. The temperature difference between the tumour and the underlying muscle thereby increased by ~1°C, indicating that SNP can increase tumour temperature during HT without increasing the risk of heat-related damage to skeletal muscle. Experiments in rats without tumours were also done to further examine the effect of SNP-hypotension on muscle temperature under different treatment conditions (variation of radiofrequency energy deposition and water bolus temperature). It was found that SNP decreased the muscle temperature during HT in two experiments where the average muscle temperature was 42.1 and 42.6°C, respectively. In an experiment where the muscle temperature was 43.0°C, on average, before SNP infusion, the muscle temperature increased during SNP-hypotension. This finding indicates that SNP-hypotension during HT may increase the risk of skeletal muscle necrosis with muscle temperatures at this level.     

Heating system with a lens applicator for 430 MHz microwave hyperthermia

To attain deep and localized heating for hyperthermic treatment of cancers, metal plate lens applicators that can converge microwave electromagnetic (EM) energy in the lossy medium such as human muscle with a computer-controlled heating system have been developed. This paper describes a system operating at 430 MHz. Results of an electric-field distribution calculation and a heating experiment made on a saline solution phantom show that the maximum heating depth is over 60 mm using the lens applicator, which is twice as deep as that obtained with a conventional waveguide applicator. The experimental results agree well with the theoretical ones. A computer-controlled heating system has been developed using the applicator. Experimental results show that fluctuations in temperature at locations in the heating region of the saline phantom were maintained within 0±3°C of the present temperatures. These results indicate that the system can be used for the clinical hyperthermia treatment of cancer.     

Locoregional hyperthermia of deep-seated tumours applied with capacitive and radiative systems: a simulation study

Background: Locoregional hyperthermia is applied to deep-seated tumours in the pelvic region. Two very different heating techniques are often applied: capacitive and radiative heating. In this paper, numerical simulations are applied to compare the performance of both techniques in heating of deep-seated tumours.

Methods: Phantom simulations were performed for small (30?×?20?×?50?cm³) and large (45?×?30?×?50?cm³), homogeneous fatless and inhomogeneous fat-muscle, tissue-equivalent phantoms with a central or eccentric target region. Radiative heating was simulated with the 70?MHz AMC-4 system and capacitive heating was simulated at 13.56?MHz. Simulations were performed for small fatless, small (i.e. fat layer typically <2?cm) and large (i.e. fat layer typically >3?cm) patients with cervix, prostate, bladder and rectum cancer. Temperature distributions were simulated using constant hyperthermic-level perfusion values with tissue constraints of 44?°C and compared for both heating techniques.

Results: For the small homogeneous phantom, similar target heating was predicted with radiative and capacitive heating. For the large homogeneous phantom, most effective target heating was predicted with capacitive heating. For inhomogeneous phantoms, hot spots in the fat layer limit adequate capacitive heating, and simulated target temperatures with radiative heating were 2–4?°C higher. Patient simulations predicted therapeutic target temperatures with capacitive heating for fatless patients, but radiative heating was more robust for all tumour sites and patient sizes, yielding target temperatures 1–3?°C higher than those predicted for capacitive heating.

Conclusion: Generally, radiative locoregional heating yields more favourable simulated temperature distributions for deep-seated pelvic tumours, compared with capacitive heating. Therapeutic temperatures are predicted for capacitive heating in patients with (almost) no fat.     

Comparison of two different 70 MHz applicators for large extremity lesions: Simulation and application

Introduction: Motivation for this research was a patient with large and bulky melanoma lesions on a leg, treated with hyperthermia in a special set-up with an open water bolus and two opposing applicators. Treatment planning was used to find the most suitable heating method, comparing 70 MHz capacitive contact flexible microstrip applicators (CFMAs) and 70 MHz waveguides.

Methods: The first three sessions were performed with CFMA applicators; the last session with waveguides. Power and water temperature were adjusted to achieve clinically relevant temperatures. Finite difference time domain (FDTD) simulations were performed for a CFMA and waveguide on a fat-muscle geometry to compare effective field size (EFS) and effective heating depth (EHD). A CT scan of the patient's leg was automatically segmented into muscle, fat and bone; tumour lesions were outlined manually. Patient simulations were performed to evaluate the 3D heating pattern and to compare CFMAs and waveguides for equal power and water temperature.

Results: Hyperthermia treatment was well tolerated. Temperature measurements indicated mainly superficial heating with CFMAs. Simulated EHD was 2.1 and 2.4 cm for CFMA and waveguide, respectively and EFS was 19.6 × 16.2 cm² and 19.4 × 16.3 cm². Simulation results showed a better tumour coverage using waveguides; absorbed power in the tumour was ～75% higher with waveguides and absorption in fat was approximately twice as high with CFMAs. Simulations showed that a relatively high water temperature (～42°C) improves the overall temperature distribution.

Conclusion: CFMAs and waveguides have a similar EFS and EHD, but for large extremity lesions, the performance of 70 MHz waveguides is favourable compared to 70 MHz CFMA applicators.     

Feasibility of on-line temperature-based hyperthermia treatment planning to improve tumour temperatures during locoregional hyperthermia

Background: The effectiveness of hyperthermia is strongly dependent on the achieved tumour temperatures. Phased-array systems allow flexible power steering to realise good tumour heating while avoiding excessive heating in normal tissue, but the limited quantitative accuracy of pre-treatment planning complicates realising optimal tumour heating. On-line hyperthermia treatment planning could help to improve the heating quality. This paper demonstrates the feasibility of using on-line temperature-based treatment planning to improve the heating quality during hyperthermia in three patients.

Methods: Hyperthermia treatment planning was performed using the Plan2Heat software package combined with a dedicated graphical user interface for on-line application. Electric fields were pre-calculated to allow instant update and visualisation of the predicted temperature distribution for user-selected phase-amplitude settings during treatment. On-line treatment planning using manual variation of system settings for the AMC-8 hyperthermia system was applied in one patient with a deep-seated pelvic melanoma metastasis and two cervical cancer patients. For a clinically relevant improvement the increase in average target temperature should be at least 0.2?°C.

Results: With the assistance of on-line treatment planning a substantial improvement in tumour temperatures was realised for all three patients. In the melanoma patient, the average measured target temperature increased from 38.30?°C to 39.15?°C (i.e.?+0.85?°C). In the cervical cancer patients, the average measured target temperature increased from 41.30?°C to 42.05?°C (i.e.?+0.75?°C) and from 41.70?°C to 42.80?°C (i.e.?+1.1?°C), respectively.

Conclusion: On-line temperature-based treatment planning is clinically feasible to improve tumour temperatures. A next, worthwhile step is automatic optimisation for a larger number of patients.     

Design of intracavitary microwave applicators for the treatment of uterine cervix carcinoma

A 915 MHz intracavitary applicator was designed to heat tumours in the cervical and upper vaginal regions. The applicator has a 3.5-turn helical coil wound around the distal 19 mm of a dielectric rod 43 mm long and 30 mm in diameter. For treating uterine cancer, a 2450 MHz, 4 mm diameter helical applicator was made by replacing 6 cm of the outer conductor of a coaxial cable with six turns of copper wire soldered to the outer conductor. The heating patterns were determined thermographically in a muscle phantom. The maximum heating rates were 0.42 and 0.83°C/W-min, respectively, for the 915 and 2450 MHz applicators. Intracavitary temperature distributions in the upper vagina, cervix and uterus were measured at the surface of the applicators with thermocouples. The average temperature was 46.0 ± 2.1°C (S. D.) at mid-tumour and 44.5 ± 0.8°C at the tumour periphery. The maximum temperature, up to 51.5°C, was measured at the surface of the cervical applicator. The majority of the patients (28/30) tolerated the investigational treatment without burns or pain. Rectal temperatures were also monitored. The location of the hot-spot (40.7°C) in the rectum, 5–7 cm above the anus, corresponded to the tip of the cervical applicator (47.1°C).     

A comparison of the heating characteristics of capacitive and radiative superficial hyperthermia

Background: Superficial hyperthermia is applied in combination with radiotherapy for e.g. melanoma and recurrent breast cancer, using both capacitive and radiative systems. In this paper, numerical simulations are applied to address the question which technique yields the most favourable heating characteristics.

Methods: A 434?MHz contact flexible microstrip applicator (CFMA type 4H, size 19.6?×?19.6?cm²) and a capacitive system consisting of two circular electrodes with diameter 15 and 25?cm were modelled. The water bolus of the CFMA was filled with deionised water and for capacitive heating both saline and deionised water were modelled. Specific absorption rate (SAR) and temperature simulations were performed for a perfused muscle-equivalent phantom and phantoms with a 1?cm thick superficial fat layer, assuming cylindrical target regions. Subsequently, a real patient model with a chest wall recurrence was studied with the target assumed to have muscle-like properties, fat properties or heterogeneous properties as derived from the CT Hounsfield Units.

Results: Phantom simulations showed that high SAR peaks occur around the bolus edges with capacitive heating. Power absorption below the fat layer is substantially higher for radiative heating and unless the target region is limited to the fat layer, radiative heating yields better target coverage in terms of SAR and temperature. Patient simulations showed that the T₉₀ for radiative heating was 0.4–1.1?°C higher compared with capacitive heating.

Conclusions: Radiative heating yields more favourable SAR and temperature distributions for superficial tumours, compared with capacitive heating, especially within heterogeneous tissues. Higher tumour temperatures are achieved without occurrence of treatment limiting hot spots.     

Localized magnetic-loop induction hyperthermia of the rabbit brain

The Magnetrode magnetic-loop applicator has been used for deep internal hyperthermia with minimal toxicity and without normal tissue injury. Until now, the effects of localized radiofrequency hyperthermia on the brain have not been adequately studied because of the potential hazards involved in trying to effect brain heating while preserving overlaying surface tissues. We found that normal rabbit brain could be heated to potentially tumoricidal temperatures (42–43°C) without apparent histopathologic or clinical damage to brain, skull, external eye, subcutaneous tissue, or skin.     

Hyperthermia treatment planning for cervical cancer patients based on electrical conductivity tissue properties acquired in vivo with EPT at 3 T MRI

Introduction The reliability of hyperthermia treatment planning (HTP) is strongly dependent on the accuracy of the electric properties of each tissue. The values currently used are mostly based on ex vivo measurements. In this study, in vivo conductivity of human muscle, bladder content and cervical tumours, acquired with magnetic resonance-based electric properties tomography (MR-EPT), are exploited to investigate the effect on HTP for cervical cancer patients. Methods Temperature-based optimisation of five different patients was performed using literature-based conductivity values yielding certain antenna settings, which are then used to compute the temperature distribution of the patient models with EPT-based conductivity values. Furthermore, the effects of altered bladder and muscle conductivity were studied separately. Finally, the temperature-based optimisation was performed with patient models based on EPT conductivity values. Results The tumour temperatures for all EPT-based dielectric patient models were lower compared to the optimal tumour temperatures based on literature values. The largest deviation was observed for patient 1 with ΔT90 = ?1.37?°C. A negative impact was also observed when the treatment was optimised based on the EPT values. For four patients ΔT90 was less than 0.6?°C; for one patient it was 1.5?°C. Conclusions Electric conductivity values acquired by EPT are higher than commonly used from literature. This difference has a substantial impact on cervical tumour temperatures achieved during hyperthermia. A higher conductivity in the bladder and in the muscle tissue surrounding the tumour leads to higher power dissipation in the bladder and muscle, and therefore to lower tumour temperatures.     

An integrated platform for small-animal hyperthermia investigations under ultra-high-field MRI guidance

Purpose: Integrating small-animal experimental hyperthermia instrumentation with magnetic resonance imaging (MRI) affords real-time monitoring of spatial temperature profiles. This study reports on the development and preliminary in vivo characterisation of a 2.45?GHz microwave hyperthermia system for pre-clinical small animal investigations, integrated within a 14 T ultra-high-field MRI scanner.

Materials and methods: The presented system incorporates a 3.5?mm (OD) directional microwave hyperthermia antenna, positioned adjacent to the small-animal target, radiating microwave energy for localised heating of subcutaneous tumours. The applicator is integrated within the 30?mm bore of the MRI system. 3D electromagnetic and biothermal simulations were implemented to characterise hyperthermia profiles from the directional microwave antenna. Experiments in tissue mimicking phantoms were performed to assess hyperthermia profiles and validate MR thermometry against fibre-optic temperature measurements. The feasibility of delivering in vivo hyperthermia exposures to subcutaneous 4T1 tumours in experimental mice under simultaneous MR thermometry guidance was assessed.

Results: Simulations and experiments in tissue mimicking phantoms demonstrated the feasibility of heating 21–982?mm³ targets with 8–12 W input power. Minimal susceptibility and electrical artefacts introduced by the hyperthermia applicator were observed on MR imaging. MR thermometry was in excellent agreement with fibre-optic temperatures measurements (max. discrepancy ≤0.6?°C). Heating experiments with the reported system demonstrated the feasibility of heating subcutaneous tumours in vivo with simultaneous MR thermometry.

Conclusions: A platform for small-animal hyperthermia investigations under ultra-high-field MR thermometry was developed and applied to heating subcutaneous tumours in vivo.     

Accurate 3D temperature dosimetry during hyperthermia therapy by combining invasive measurements and patient-specific simulations

Abstract

Purpose: Dosimetry during deep local hyperthermia treatments in the head and neck currently relies on a limited number of invasively placed temperature sensors. The purpose of this study was to assess the feasibility of 3D dosimetry based on patient-specific temperature simulations and sensory feedback. Materials and methods: The study includes 10 patients with invasive thermometry applied in at least two treatments. Based on their invasive thermometry, we optimised patient-group thermal conductivity and perfusion values for muscle, fat and tumour using a ‘leave-one-out’ approach. Next, we compared the accuracy of the predicted temperature (ΔT) and the hyperthermia treatment quality (ΔT50) of the optimisations based on the patient-group properties to those based on patient-specific properties, which were optimised using previous treatment measurements. As a robustness check, and to enable comparisons with previous studies, we optimised the parameters not only for an applicator efficiency factor of 40%, but also for 100% efficiency. Results: The accuracy of the predicted temperature (ΔT) improved significantly using patient-specific tissue properties, i.e. 1.0?°C (inter-quartile range (IQR) 0.8?°C) compared to 1.3?°C (IQR 0.7?°C) for patient-group averaged tissue properties for 100% applicator efficiency. A similar accuracy was found for optimisations using an applicator efficiency factor of 40%, indicating the robustness of the optimisation method. Moreover, in eight patients with repeated measurements in the target region, ΔT50 significantly improved, i.e. ΔT50 reduced from 0.9?°C (IQR 0.8?°C) to 0.4?°C (IQR 0.5?°C) using an applicator efficiency factor of 40%. Conclusion: This study shows that patient-specific temperature simulations combined with tissue property reconstruction from sensory data provides accurate minimally invasive 3D dosimetry during hyperthermia treatments: T50 in sessions without invasive measurements can be predicted with a median accuracy of 0.4?°C.     

Response of 145 spontaneous canine head and neck tumours to radiation versus radiation plus microwave hyperthermia: Results of a randomized phase III clinical study

The results of a phase III, clinical trial of local microwave hyperthermia (target = 2 × 44°C for 30 min) and megavoltage radiation (4 × 9 Gy fractions) in the treatment of 145 naturally occurring canine head and neck cancers are reported. Patients were re-examined at regular intervals following treatment until death. The median follow up time was 90 weeks. Tumour response, patient survival and normal tissue toxicity were analysed by treatment allocation. There was no significant difference in best tumour response nor patient survival between the two treatment groups. There was no difference in acute normal tissue toxicity but there was a suggestion that patients receiving RT and HT may suffer a higher incidence of late skin reactions. Histological type and tumour volume were of prognostic significance with smaller tumours and carcinomas showing higher response rates. There were also positive associations between minimum tumour dose and best tumour response and percentage of tumour heated and best tumour response. The results of this study must be interpreted in the knowledge of limitations on the dose and fractionation schedule for radiation therapy, the small number of hyperthermia treatments applied and the variation in tumour type and size that is inevitable in a clinical study. It is concluded that the quality of hyperthermia in terms of intra-tumour temperatures and the uniformity of heating is of paramount importance in governing response to adjuvant hyperthermia.     

Thermal therapy of pancreatic tumours using endoluminal ultrasound: Parametric and patient-specific modelling

Purpose: The aim of this study is to investigate endoluminal ultrasound applicator configurations for volumetric thermal ablation and hyperthermia of pancreatic tumours using 3D acoustic and biothermal finite element models. Materials and methods: Parametric studies compared endoluminal heating performance for varying applicator transducer configurations (planar, curvilinear-focused, or radial-diverging), frequencies (1–5 MHz), and anatomical conditions. Patient-specific pancreatic head and body tumour models were used to evaluate feasibility of generating hyperthermia and thermal ablation using an applicator positioned in the duodenal or stomach lumen. Temperature and thermal dose were calculated to define ablation (>?240 EM_43?°C) and moderate hyperthermia (40–45?°C) boundaries, and to assess sparing of sensitive tissues. Proportional-integral control was incorporated to regulate maximum temperature to 70–80?°C for ablation and 45?°C for hyperthermia in target regions.

Results: Parametric studies indicated that 1–3 MHz planar transducers are the most suitable for volumetric ablation, producing 5–8?cm³ lesion volumes for a stationary 5-min sonication. Curvilinear-focused geometries produce more localised ablation to 20–45?mm depth from the GI tract and enhance thermal sparing (T_max?<?42?°C) of the luminal wall. Patient anatomy simulations show feasibility in ablating 60.1–92.9% of head/body tumour volumes (4.3–37.2?cm³) with dose?<?15 EM_43?°C in the luminal wall for 18–48 min treatment durations, using 1–3 applicator placements in GI lumen. For hyperthermia, planar and radial-diverging transducers could maintain up to 8?cm³ and 15?cm³ of tissue, respectively, between 40–45?°C for a single applicator placement. Conclusions: Modelling studies indicate the feasibility of endoluminal ultrasound for volumetric thermal ablation or hyperthermia treatment of pancreatic tumour tissue.     

Metamaterial lens applicator for microwave hyperthermia of breast cancer

Artificial left-handed metamaterial (LHM) provides a new perspective for microwave hyperthermia. Four flat LHM slab lenses can be used to form a focus-flexible applicator for breast tumour hyperthermia. By adjusting microwave sources behind the four flat LHM lenses, microwaves emitted from the sources can be focused tightly at different points in the breast tissue so that necessary heating depth in breast tissue can be achieved. Numerical simulations with a two-dimensional finite-difference time-domain method indicate that hyperthermia with the proposed four-lens applicator of moderate LHM losses could be effective in achieving desired power deposition in a heterogeneous breast model. Temperature distribution obtained by solving the bio-heat transfer equation demonstrates that temperature above 43°C can be maintained in the tumour volume for specific periods of time. Flat slab LHM lenses offer a feasible alternative to traditional mechanically scanned lens applicator and electronically scanned phased-array applicators.     

Short communication: Intracavitary hyperthermia applicators for treating nasopharyngeal and cervical cancers

Many intracavitary microwave applicators have been designed to heat tissues along the side of an antenna. For tumours in nearly closed-end cavities such as the nasopharynx and cervix, heating near the tip of the applicators is necessary for effective treatment. A nasopharyngeal applicator made of Micro Coax UT-250A and a cervical applicator made of RG-9/U cables were designed to provide heating at the tip. Return losses of 8–12 dB were obtained at 915 MHz by varying the size of two metal sleeves and adjusting the distance between these sleeves and the reflectors at the applicator tips. Heating patterns were evaluated on a muscle phantom with a thermograph. At 915 MHz, maximum heating rates of 1·3 and 0·85°C/W-min, respectively, were observed near the tip of the nasopharyngeal applicator and at its first sleeve opening. When operated at 915 MHz the cervical applicator has a maximum heating rate of 0·25°C/W-min at the tip. Clinically, both applicators require a maximum power of 30 W to provide effective heating. This makes it possible to provide intracavitary hyperthermia at rural hospitals and small clinics with a small portable system.     

Relation between body size and temperatures during locoregional hyperthermia of oesophageal cancer patients

Purpose. To analyse the relation between patients’ body size and temperatures during locoregional hyperthermia for oesophageal cancer.

Methods. Patients were treated with neo-adjuvant chemoradiotherapy plus hyperthermia, given with the AMC-4 waveguide system. Temperatures were measured at tumour location in the oesophageal lumen using multisensor thermocouple probes. Systemic temperature rise (ΔT_syst) was monitored rectally. Steady-state tumour temperatures were expressed in terms of T₉₀, T₅₀ and T₁₀, averaged over the five hyperthermia sessions, and correlated with patients’ body mass, dorsoventral and lateral diameter and fat layer thickness, measured at tumour level using a CT scan made in treatment position. Fat percentage (Fat%) was estimated using diameters and fat layer thickness. Effective tumour perfusion (W_b) was estimated from the temperature decay during the cool-down period.

Results. Temperatures were inversely related to body mass, diameters, fat layer thickness, and fat percentage. The strongest univariate correlations were found with lateral fat layer thickness, lateral diameter, and body mass. An increase in lateral diameter (28→42 cm), or in lateral fat layer thickness (0→40 mm) or in body mass (50→120 kg) all yielded a ～1.5°C decrease in tumour temperature rise. Multivariate correlation analysis proved that the combination of Fat%, ΔT_syst and W_b was most predictive for the achieved tumour temperatures, accounting for 81 ± 12% of the variance in temperatures.

Conclusions. Intra-oesophageal temperatures during locoregional hyperthermia are inversely related to patients’ body size parameters, of which fat percentage is the most significant prognostic factor. These findings could be used to define inclusion criteria of new studies on intrathoracic hyperthermia.     

Changes in hepatic blood flow during regional hyperthermia

The influence of liver hyperthermia on hepatic arterial and portal venous blood flow to tumour and normal hepatic tissue was examined in a rabbit VX2 tumour model. Hyperthermia was delivered by 2450 MHz microwave generator to exteriorized livers in 18 rabbits. Blood flow was measured in both portal vein and hepatic artery using radioactive tracer microspheres before, during and 5 min after intense (>43°C) hyperthermia. During hyperthermia a decrease in total liver blood flow was composed primarily of a decrease in hepatic arterial blood flow to tumour tissue. Tumours were supplied almost exclusively by the hepatic artery and thus total tumour blood flow was significantly depressed during heating. The decreased tumour blood flow persisted after the cessation of hyperthermia and was indicative of vascular collapse in the tumour tissue. Temperature differentials in tumour compared to normal tissue ranged from 5°C to 8°C during hyperthermia because of the lower tumour blood flow. The portal vein exerted minimal influence on temperatures attained in the tumour tissue during hyperthermia but would have mediated normal liver tissue heat loss.     

Radiofrequency hyperthermia in the palliative treatment of mucinous carcinomatosis of appendiceal origin: optimizing and monitoring heat delivery in western patients

rate of 62% was caused by the long-term indwelling temperature probe sheaths. Infection was observed in four patients, small bowel fistula in one, and dislodgement of the temperature probe sheath requiring repeat CT was necessary in seven patients. After maximal escalation of RF power in seven patients (33%), deep hyperthermia compatible with thermal destruction of tumour (43°C for 45 min) was recorded in all subsequent treatments. In eight patients (38%), heat generation compatible with chemotherapy augmentation (41.5-43°C) was consistently recorded. In six patients, non-therapeutic temperatures were recorded. There was no correlation of maximal tumour temperature, maximal subcutaneous tissue temperature and maximal RF power. With the use of skin anaesthetic there was no correlation of tumour temperature and the thickness of the subcutaneous layer of the skin. Progression was seen in 14 patients, and 11 of these patients died. No patients who showed disease stabilization have died with a minimum of 2 year follow-up. Approximately 2/3 of Western patients can safely tolerate deep hyperthermia compatible with thermal destruction or chemotherapy augmentation with the use of skin anaesthetics. Thermal monitoring remained a problem in this investigation, in that there was a high incidence of adverse events. Increased temperature measured in subcutaneous tissue and tumour did not show a correlation with each other, with RF power, or with occurrence of complications. With localized mucinous tumours of appendiceal origin, deep hyperthermia with escalations of heat to maximal levels tolerated by the patient should continue to be pursued for a remarkable prolonged survival and excellent quality of life was seen in selected patients.