Magnetic-induction hyperthermia. Results of a 5-year multi-institutional national cooperative trial in advanced cancer patients

Magnetic nanoparticle biodistribution following intratumoral administration

Recently, heat generated by iron oxide nanoparticles (IONPs) stimulated by an alternating magnetic field (AMF) has shown promise in the treatment of cancer. To determine the mechanism of nanoparticle-induced cytotoxicity, the physical association of the cancer cells and the nanoparticles must be determined. We have used transmission electron microscopy (TEM) to define the time dependent cellular uptake of intratumorally administered dextran-coated, core-shell configuration IONP having a mean hydrodynamic diameter of 100-130 nm in a murine breast adenocarcinoma cell line (MTG-B) in vivo. Tumors averaging volumes of 115 mm3 were injected with iron oxide nanoparticles. The tumors were then excised and fixed for TEM at time 0.1-120 h post-IONP injection. Intracellular uptake of IONPs was 5.0, 48.8 and 91.1% uptake at one, 2 and 4 h post-injection of IONPs, respectively. This information is essential for the effective use of IONP hyperthermia in cancer treatment.

Technologic innovations in surgery: a philosophic reflection on their impact on operations for cancer

Technologic advances this past half-century have clearly had a positive effect on our ability to both diagnose and treat human cancer as well as on the operative treatment of other diseases. However, the impact of these innovations on the surgical treatment of cancer is not as clear as it is for many other problems that are managed surgically. This review is an "opinion piece" that attempts to assess the successes and failures of technologic innovations that have been introduced for the purpose of improving the operative treatment of cancer.

Evolving technology for thermal therapy of cancer

This paper is intended as a succinct review of technology used for clinical hyperthermia therapy for cancer, as culled from a presentation at the special workshop on Thermal Medicine, Heat Shock Proteins, and Cancer at the Society for Thermal Medicine conference in Spring 2005. Following a brief overview of thermal therapy treatment options and available mechanisms for heating tissue, the paper focuses on the evolution of equipment from basic single element heating devices of the early 1980s to adjustable multi-element heating devices currently in use or in final stages of development. Representative devices from the past, present and near future are cited for further investigation by the interested reader. The paper concludes with a summary of general trends in the evolution of clinical hyperthermia techniques and a statement of current challenges remaining for the field.

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.

Antitumour activity of 5-fluorouracil, verapamil and hyperthermia against human gastric adenocarcinoma cell (AGS) in vitro

The purpose of this study was to assess the efficacy of verapamil (20 microM) and hyperthermia (42 degrees C) as modifiers of 5-fluorouracil (5-FU), used at different concentrations, in inhibiting the growth of gastric adenocarcinoma cells. Combined verapamil and hyperthermia treatment showed a significant decrease in cell count when compared to control (72.2%), hyperthermia alone (68.4%), or verapamil alone (65%). At a high concentration of 5-FU (50 micrograms/ml), verapamil and hyperthermia had an additive growth inhibitory effect over a 4-day period when compared to control. A combination of 5-FU at low concentration (0.5 microgram/ml) with verapamil significantly suppressed growth by 31.2% in comparison to control--with this effect being independent of the duration of treatment. The modalities analysed in this study require further investigation and have potential for clinical applicability to gastric cancer therapy in the future.

Chemotherapy combined with or without hyperthermia for patients with oesophageal carcinoma: a prospective randomized trial

From 1990 to 1991, 40 patients with squamous cell carcinoma of the thoracic oesophagus were admitted to our institutions and chemotherapy (oil Bleomycin p.o. and CDDP d.i.v.) either combined with or without hyperthermia was performed, in a prospective randomized trial carried out to investigate the effects of hyperthermia. The two groups (group A, consisting of 20 patients given chemotherapy alone; and group B, made up of 20 given chemotherapy with hyperthermia) were comparable with regard to various prognostic factors. Following the above treatment regimens, an oesophagectomy was done in 16 and 17 patients from groups A and B, respectively. A subjective improvement of dysphagia was seen in 8 (40.0%), and in 14 patients (70.0%), while a radiographic improvement was recognized in 5 (25.0%) and 10 cases (50.0%) in groups A and B, respectively. In the resected specimen of 16 (group A) and 17 patients (group B), histopathological evidence of the effectiveness of the treatments were recognized in 3 (18.8%) and 7 (41.2%) from groups A and B, respectively. Excluding the cases of superficial carcinoma (T1 tumour), histologic effectiveness of the treatments were recognized in 2 (14.3%) and 7 (58.3%) in groups A and B, respectively (p < 0.05). There was no difference in the occurrence of side effects between the groups. Therefore, the clinical and pathological effects were favourable in the hyperthermia combined with chemotherapy group, especially in the cases with advanced oesophageal cancer.

Enhancement of hyperthermic toxicity by lonidamine in the Dunning R3327G rat prostatic adenocarcinoma

Hyperthermia alone or with radiation is used therapeutically for localized solid tumors. Clinical experience shows that sustained tumor temperature exceeding 45 degrees C damages normal tissue. Any agent that enhances the effects of hyperthermia at or below this temperature may have clinical relevance. Lonidamine and hyperthermia were tested on the Dunning R3327G rat prostatic adenocarcinoma. Using colony-formation assays, cytotoxic effects of each agent alone and in combination were quantified. Lonidamine to 100 micrograms/ml was not significantly toxic, but in combination, it enhanced cytotoxicity. Survival patterns after fractionated hyperthermia revealed a rapid development and decay of thermotolerance. Measurement of cell-cycle progression following a single dose of hyperthermia revealed a reduction of S-phase cells, and subsequent accumulation in G1 over 24 hours. Combination treatment of tumor-bearing rats significantly reduced tumor growth rate when compared with individual agents. These results suggest a potential use of lonidamine in hyperthermic therapy of prostate tumors.

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.

Hyperthermia in cancer growth regulation

With present techniques, hyperthermia used alone can cause complete clinical regression in 10-15% of tumours but the duration of response is very short. The greatest advantage for hyperthermia at the present time appears to be in combination with radiation in the local control of cancer growth. Currently, large randomised phase III studies are in progress to determine whether the addition of local hyperthermia to radiation or chemotherapy yields significant advantage. Phase III studies of wholebody hyperthermia in combination with chemotherapy are planned for the future and will include tumours with a high growth fraction such as small cell lung cancer and high grade non Hodgkins lymphoma.

Correlation of thermal parameters with outcome in combined radiation therapy-hyperthermia trials

Many studies utilizing combined hyperthermia (HT) and radiation therapy (XRT) in the treatment of advanced or recurrent malignancies have reported a correlation between some measure of the minimum temperature achieved and outcome. Previous reported studies at Stanford have demonstrated a statistically significant correlation between the duration of local control and Tmin, the mean over treatments of the minima of (a) measured intratumoral temperatures in fields which contained diffuse or nodular tumours, or (b) measured interstitial temperatures in fields treated for microscopic residual disease. Recently, T90, the mean of the temperatures above which 90% of all measured intratumoral temperatures fall, has been proposed as an alternative characterization of the efficacy of the HT treatment that reportedly has a superior correlation with outcome. To test this hypothesis, T90 was computed by two different methods for three groups of patients treated at Stanford with XRT-HT for superficially located tumor recurrences. Tmin was found to be strongly correlated with T90 calculated by both methods. All three thermal parameters correlated with complete response at 3 weeks and with local control, although Tmin usually demonstrated the strongest correlation.

Hyperthermia combined with chemotherapy and irradiation for patients with carcinoma of the oesophagus--a prospective randomized trial

From 1988 to 1990, 53 patients with squamous cell carcinoma of the thoracic oesophagus underwent subtotal oesophagectomy after either preoperative hyperthermo-chemoradiotherapy (HCR therapy) or chemoradiotherapy without hyperthermia (CR therapy), in a prospective randomized trial carried out to examine the effects of hyperthermia given preoperatively. The two groups (27 patients given HCR therapy and 26 given CR therapy) were found to be comparable with regard to prognostic factors of age, site of carcinoma, TNM stage, etc. Following preoperative evaluation by an upper GI series and endoscopy, a subtotal oesophagectomy was done for all 53 patients. All the resected specimens, including the lymph nodes, were histopathologically examined, and the effects of preoperative treatment were evaluated by findings in the upper GI series and endoscopy, as well as based on the histopathology of the excised tissues. There were no viable cancer cells in the resected specimens of seven patients in the HCR therapy group (26.9%) and of two patients in the CR therapy group (7.7%). In addition, no hyperthermia complications were observed. The study suggests that preoperative HCR therapy may be a more beneficial therapy than preoperative CR therapy in patients with squamous cell carcinoma of the oesophagus who undergo a subtotal oesophagectomy.

Effects of multimodal treatment and hyperthermia on hepatic tumors

The therapeutic results of Lp-TAE (transcatheter arterial embolization in the presence or absence of Gelfoam particles preceded by the infusion of a mixture of lipiodol and an anticancer drug via the proper hepatic artery) or DSM-TAE (transcatheter arterial embolization with degradable starch microspheres and the arterial injection of anticancer drugs via the hepatic artery) combined with hyperthermia were evaluated in 30 patients with hepatocellular carcinoma (HCC), 5 subjects with hepatic cholangiocarcinoma, and 22 patients with metastatic liver carcinoma. Hyperthermia was performed using an 8-MHz Thermotron RF-8. Tumor temperatures could be measured in 31 patients (54.4%) with malignant lesions of the liver who had undergone hyperthermia. The mean maximal temperature (Tmax) was 41.5 degrees C in the metastatic liver cancers. The efficiency of heating in HCC was unfavorable, i.e., the mean Tmax was only 40.7 degrees C. The rise in tumor temperature was greater in either HCC or metastatic liver carcinoma associated with portal invasion of the lesion. The tumor-temperature elevation was also excellent in HCC that had been subjected to embolization with DSM in combination with hyperthermia. The response rate (complete response plus partial response) was as high as 40% (4/10) in the group in which the tumor temperature could be raised to 42 degrees C or more. Among the 52 patients who had shown a high pretreatment level of tumor marker, that value decreased in 34 cases (65.4%), and the decrease was greater than 50% in 22 cases (42.3%).

Regional hyperthermia combined with radiotherapy in the treatment of lung cancers

Twenty locally advanced lung cancers were treated by hyperthermia in combination with radiotherapy between November 1980 and January 1990. All tumors selected had invaded or were in contact with the chest wall, so that transcutaneous insertion of thermal probes into the tumor was possible. Using an 8 or 13.56 MHZ RF capacitive heating device, hyperthermia was given once or twice a week after irradiation for 30-60 min per session (1-12 sessions in total). Radiotherapy was delivered at dose of 13.6-70 Gy. The thermal parameters analyzed were a) maximum, average, and minimum intratumor temperatures (Tmax, Tav, and Tmin), which were recorded at the termination of each treatment, and b) the percentages of the intratumor points that exceeded 41 C (%T greater than or equal to 41 C). The mean +/- SD for Tmax, Tav, Tmin, and %T greater than or equal to 41 C was 42.9 +/- 1.7 C, 41.6 +/- 1.2 C, 39.7 +/- 1.1 C, and 56.2 +/- 25.8, respectively. Larger tumors showed higher thermal parameters than the smaller tumors. Of the 12 tumors treated by definitive therapy, 2 (17%) achieved CR, 7 (58%) PR, and 3 (25%) NR. Four of 10 tumors that did not achieve CR showed large intratumor low density areas on post-treatment CT, reflecting massive coagulation necrosis. Higher thermal parameters were closely related to the appearance of low-density areas but not to changes in tumor size. Four tumors treated preoperatively were successfully resected 2 weeks after thermoradiotherapy, whereas four palliatively-treated tumors showed no regression. The side effects associated with hyperthermia were pain in 12 patients (60%) and dyspnea in 3 (15%), all of which resolved after termination of treatment. A skin abscess and a pneumothorax attributed to thermal probe insertion were observed in one patient each. These results indicate that regional RF capacitive hyperthermia is clinically feasible for local treatment of selected lung cancers.

Hyperthermia alone in the treatment of recurrences of malignant tumors. Experience with 60 lesions

Localized hyperthermia alone has been used for the treatment of cancer recurrences in which previous conventional therapies have failed. Since 1983 and 1988, 57 patients with 60 lesions have been heated by means of a microwave and radiofrequency system. Treatment protocol provided 45 minutes of heating at the intratumor temperature of at least 42 degrees C, twice a week, for a total number of six, eight, or ten heating sessions. Invasive intratumor thermometry was performed for all lesions. Complete response (CR) was obtained in ten cases (16.6%) and partial response (PR) in 14 (23.4%). Higher rates of CR were observed in the chest wall (38.5%) compared with the head and neck area (11.4%), trunk (10%), and limbs (none). Adenocarcinoma was the most responsive histologic type (40%). Squamous cells carcinoma had 7.7% CR. The only case of undifferentiated carcinoma showed CR; there were none on five sarcomas. Long-term local control (24 months) was approximately 7%. The multivariate analysis showed the statistical significance of the histologic variety (adenocarcinoma versus others, P less than 0.0001). Side effects and complications of the treatment were minimal.

Thermal enhancement of radiation-induced leg contracture

Early and late damage in the normal tissues of the legs of mice was compared following treatment with radiation alone or radiation followed immediately by hyperthermia. Hyperthermia was given by immersing the hind leg in a water bath at 43.0 degrees, 43.3 degrees, or 43.5 degrees C for 1 hr. Damage was assayed by measuring leg contracture at various intervals from 5 to 365 days after treatment. At 5 days after treatment, only hyperthermia-induced contracture was observed. At 10 and 20 days, contracture increased with radiation dose in heated legs, but little contracture had developed in mice treated with radiation alone. By 45 through 365 days, however, contracture correlated with radiation dose both in mice treated with radiation alone as well as in those treated with radiation and hyperthermia. The greatest differential in the slopes of the dose response curves, suggesting hyperthermic radiosensitization, was seen 20 days after treatment. Nevertheless, at 365 days, contracture was still significantly greater in the mice treated with radiation and hyperthermia (43.5 degrees bath) than in the irradiated controls. Thermal enhancement ratios (TERs) were calculated from LCD50 values (LCD50 = radiation dose that would give a stated level of leg contracture in 50% of the mice). For greater than or equal to 3 mm contracture, TERs were 4.1 to 7.9 at 30 days, depending on bath temperature, but only 1.1 to 1.5 at 365 days. For an isoeffect of greater than or equal to 7 mm contracture, TERs were 1.9 to 5.3 at 30 days, and 0.8 to 1.8 at 365 days. Thus, contracture was enhanced more at 20 to 30 days after treatment with radiation and hyperthermia than at 120 through 365 days. Radiation damage not only appeared earlier in mice treated with hyperthermia than in those treated with radiation alone, but after the highest temperature tested (43.5 degrees bath), contracture was greater from 5 through 365 days after treatment than in controls treated with radiation alone.

Radiofrequency (RF) capacitive hyperthermia combined with radiotherapy in the treatment of abdominal and pelvic deep-seated tumors

Thermal parameters and tumor response were determined in 33 abdominal and pelvic deep-seated tumors which were treated with hyperthermia in combination with radiation therapy. Hyperthermia was applied regionally for a total of 3-14 sessions (mean; 6.4 sessions), using an 8 MHz radiofrequency (RF) capacitive heating device. An average tumor temperature (Tav) of more than 42 degrees C was achieved in 17 (52%) tumors, and intratumor temperatures above 42 degrees C could be maintained for more than 20 min (effective heat session) in 103 (52%) of the 198 heat sessions. Of the 33 tumors, 4 tumors exhibited complete regression (CR), 7 PRa (80-99% regression), 7 PRb (50-79% regression) and 15 NR (less than 50% regression). Tumor response (CR + PRa) was apparently dependent on the thermal parameters. Tumors with Tav of more than 42 degrees C or those receiving more than three effective heat sessions showed a significantly higher response rate than those heated less effectively. This trend was also noted in minimum tumor temperature. As to radiation dose, most of the responders received a total of 60-70 Gy irradiation. The two characteristic features in tumor response in effectively heated tumors, were slow tumor regression and appearance of an intratumor low density area on post-treatment computed tomography.

Fluorescein isothiocyanate staining intensity as a probe of hyperthermia-induced changes in chromatin conformation

In a previous report we presented evidence for large increases in fluorescein isothiocyanate (FITC) fluorescent intensity caused by hyperthermia which were not associated with synthesis of heat-shock proteins. We have now refined and considerably extended the measurements of increases in FITC fluorescent intensity caused by hyperthermia within the range 41.0 degrees C to 50.0 degrees C, and associated these with the extent of cell death caused by the hyperthermia. It appears that cell death ensues when the FITC fluorescent intensity has not returned to its baseline value within the time of one cell cycle. If thermotolerance is induced, there is a concomitant reduction in the increase in FITC staining intensity and the extent of cell death. When hyperthermia is followed by acid extraction, an additional increase in FITC staining intensity (above that due to hyperthermia alone) is observed, indicating separate sites of action on basic nuclear proteins. Hyperthermia and acid extraction have related effects on the relationship between FITC and propidium iodide staining. Hyperthermia-induced increases in FITC staining intensity are almost completely reversed by 6.7 mM formaldehyde with a marginal effect on the control FITC staining at this formaldehyde concentration. We suggest that hyperthermia causes extensive dissociation of basic protein-protein binding within nuclear chromatin, and that this may be a contributory cause of hyperthermia-induced cell death.

Evaluation of high-intensity therapeutic ultrasound irradiation in the treatment of experimental hepatoma

A study evaluating the efficacy of high-intensity therapeutic ultrasound (HITU) as a treatment modality in experimental hepatoma is reported. Morris hepatoma (3924) 1 x 10(6) cells were transferred subcutaneously into 40 male ACI rats (weight, 150 to 200 g). Animals were divided into four experimental groups: group 1 (n = 10) consisted of untreated controls; group 2 (n = 10) received intraperitoneal cyclophosphamide 50 mg/kg as a single dose; group 3 (n = 10) underwent HITU only; and group 4 (n = 10) received both chemotherapy (as in group 2) and HITU (as in group 3). HITU was administered with a 5.5-cm diameter 4-MHz quartz transducer creating a continuous wave with 400 W/cm2 focal intensity. The entire tumor was irradiated in 1-mm increments (horizontal and vertical) using treatment cycles of 4 seconds on and 11 seconds off. Total body weight and tumor volume were measured on the day of treatment, and 4 weeks later. At 4 weeks, the animals were killed, the tumor was excised and weighed, and tumor volume was determined. Tumor volume in all treated animals (groups 2, 3 and 4) was significantly smaller than in controls (P less than .001) at 4 weeks, and tumor volume for animals in group 4 was significantly smaller than for those in groups 2 and 3 (P less than .01). These data indicate that HITU significantly reduces tumor size when compared with control rats with Morris hepatoma. A synergistic effect of chemotherapy and HITU was observed and resulted in an enhanced tumor response and reduction of tumor size.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermal dose-response of magnetic-induction thermoradiotherapy

Sixty-three patients with advanced cancer underwent greater than or equal to 5,000 cGy combined with Concentric Coil magnetic-induction localized hyperthermia. Tumor regression (CR + PR) was compared to thermal dose received, incorporating the premise that hyperthermia response is a function of time as well as temperature. A computer program was developed (after Sapareto and Dewey [2]) which stored minimum tumor temperatures recorded spatially and temporally during treatment and correlated response with T43 (equivalent minutes at 43 degrees C during the first treatment) and CT43 (cumulative T43, computed by multiplying T43 by the actual number of identical subsequent treatments received during the course of therapy). Those who responded--N = 46 (73%)--had significantly higher median thermal doses than those who did not respond. Comparison of T43 and CT43 thermal dose values between responders and nonresponders was significantly different at p values of 0.05 and 0.04, respectively. The data indicate that magnetic-induction hyperthermia and high-dose XRT was an effective treatment combination in advanced disease and that tumor response improved as thermal dose increased.

Thermal resistance of human malignant melanoma modulated by prostaglandin E2

The inhibition of DNA synthesis in a human malignant melanoma cell line as measured by tritiated thymidine (3H-TdR) incorporation was both time- and temperature dependent. Two components of cell damage were identified: a cytostatic, temporary component from which cells recovered within 2-6 days, and a cytotoxic, permanent component from which no recovery was observed. Thermotolerance was induced in M14 cells by sublethal heat treatment at 41 degrees C for 1 hr. However, induction of thermotolerance was blocked by indomethacin, a prostaglandin synthetase inhibitor. Exogenous PGE2 at concentrations up to 10 micrograms/ml also protected cells from heat damage. These data suggest that prostaglandin synthesis increases during heat stress and may play a role in protecting cells from thermal damage.

Tumor stabilization after hyperthermia: an important criterion of response to thermal therapy

Several investigators have indicated that changes in tumor size may not occur after hyperthermia therapy even with substantial tumor cell kill, because of early edema and subsequent fibrosis of background stroma, suggesting that "tumor stabilization" might be an important benefit of thermal therapy. Recently, 9 institutions completed a national cooperative study of localized hyperthermia for patients with advanced, recurrent, or metastatic solid cancer that evaluated the potential significance of this response variable in a standardized clinical trial. Of 960 evaluable patients who completed at least one course of hyperthermia, thermoradiotherapy, or thermochemotherapy, 85 (9%) had complete responses for 1-34 months, 173 (18%) had partial responses for 1-39 months, 95 (10%) had minimal responses for 1-15 months, and 313 (33%) had disease stabilization for 1-32 months. Of 313 patients who had no change (i.e., +/- 25%) in the size of their tumors after hyperthermia, the response lasted only 1-3 months in 170 (54%) patients, a finding of questionable clinical significance. However, disease stabilization was observed for more than 3 months in 143 (46%), for more than 6 months in 67 (21%), more than 9 months in 33 (10%), and more than 12 months in 16 (5%). Disease stabilization was also associated with improved activity for 1-22 months in 79 (25%) of these patients, and improved pain for 1-22 months in 100 (32%). Disease stabilization appeared to be independent of tumor histology, location, or depth within the body, size, or minimum treatment temperature, but was somewhat more frequent after hyperthermia combination therapy. There is sufficient accumulative data to suggest that tumor stabilization after hyperthermia should not be dismissed as a placebo effect. This response variable well may be a unique and potentially important criterion of response to localized hyperthermia therapy.

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.

Thermoradiotherapy for persistent cancer in previously irradiated fields

Among some 300 patients undergoing clinical trails with localized radiofrequency hyperthermia, 42 whose cancers had persisted or recurred after conventional radiotherapy were selected for additional limited radiation plus hyperthermia. There were 10 complete responses to therapy, 13 partial responses and one patient was considered nonevaluable. In the remaining 18 patients there was minor regression, stabilization or progression of the tumor. After completion of treatment, five of the tumors appeared operable and surgical resection was accomplished in four. The results of this study support the concept that hyperthermia has a potentiating effect when used in conjunction with radiation therapy.

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.