Clinical outcome of intraoperative pelvic hyperthermochemotherapy for patients with Dukes' C rectal cancer

Heating technology for malignant tumors: a review

The therapeutic application of heat is very effective in cancer treatment. Both hyperthermia, i.e., heating to 39-45 °C to induce sensitization to radiotherapy and chemotherapy, and thermal ablation, where temperatures beyond 50 °C destroy tumor cells directly are frequently applied in the clinic. Achievement of an effective treatment requires high quality heating equipment, precise thermal dosimetry, and adequate quality assurance. Several types of devices, antennas and heating or power delivery systems have been proposed and developed in recent decades. These vary considerably in technique, heating depth, ability to focus, and in the size of the heating focus. Clinically used heating techniques involve electromagnetic and ultrasonic heating, hyperthermic perfusion and conductive heating. Depending on clinical objectives and available technology, thermal therapies can be subdivided into three broad categories: local, locoregional, or whole body heating. Clinically used local heating techniques include interstitial hyperthermia and ablation, high intensity focused ultrasound (HIFU), scanned focused ultrasound (SFUS), electroporation, nanoparticle heating, intraluminal heating and superficial heating. Locoregional heating techniques include phased array systems, capacitive systems and isolated perfusion. Whole body techniques focus on prevention of heat loss supplemented with energy deposition in the body, e.g., by infrared radiation. This review presents an overview of clinical hyperthermia and ablation devices used for local, locoregional, and whole body therapy. Proven and experimental clinical applications of thermal ablation and hyperthermia are listed. Methods for temperature measurement and the role of treatment planning to control treatments are discussed briefly, as well as future perspectives for heating technology for the treatment of tumors.

Quo Vadis Oncological Hyperthermia (2020)?

Heating as a medical intervention in cancer treatment is an ancient approach, but effective deep heating techniques are lacking in modern practice. The use of electromagnetic interactions has enabled the development of more reliable local-regional hyperthermia (LRHT) techniques whole-body hyperthermia (WBH) techniques. Contrary to the relatively simple physical-physiological concepts behind hyperthermia, its development was not steady, and it has gone through periods of failures and renewals with mixed views on the benefits of heating seen in the medical community over the decades. In this review we study in detail the various techniques currently available and describe challenges and trends of oncological hyperthermia from a new perspective. Our aim is to describe what we believe to be a new and effective approach to oncologic hyperthermia, and a change in the paradigm of dosing. Physiological limits restrict the application of WBH which has moved toward the mild temperature range, targeting immune support. LRHT does not have a temperature limit in the tumor (which can be burned out in extreme conditions) but a trend has started toward milder temperatures with immune-oriented goals, developing toward immune modulation, and especially toward tumor-specific immune reactions by which LRHT seeks to target the malignancy systemically. The emerging research of bystander and abscopal effects, in both laboratory investigations and clinical applications, has been intensified. Our present review summarizes the methods and results, and discusses the trends of hyperthermia in oncology.

Therapeutic hyperthermia

The term hyperthermia broadly refers to either an abnormally high fever or the treatment of a disease by the induction of fever. Its effect depends on the temperature and exposure time. The increasing number of applications and clinical trials at universities, clinics, and hospitals prove the feasibility and applicability of clinical therapeutic hyperthermia. This chapter aims to outline and discuss the means by which electromagnetic energy and other techniques can provide elevation of temperature within the human body. Because of the individual characteristic of each type of treatment, different modalities of heating systems have evolved. The chapter concludes with a discussion of challenges and opportunities for further improvement in technology and routine clinical application.

Focused microwave phased array thermotherapy for ablation of early-stage breast cancer: results of thermal dose escalation

BACKGROUND

Tumor ablation as a means of treating breast cancer is being investigated. Microwave energy is promising because it can preferentially heat high-water-content breast carcinomas, compared to adipose and glandular tissues.

METHODS

This is a prospective, multicenter, nonrandomized dose-escalation study of microwave treatment. Thermal dose was measured as (1) thermal equivalent minutes (cumulative equivalent minutes; CEM) of treatment relative to a temperature of 43 degrees C and (2) peak tumor temperature. Microwaves were guided by an antenna-temperature sensor placed percutaneously into the tumor. Outcomes measured were pathologic response (tumor necrosis) side effects.

RESULTS

Twenty-five patients (mean age, 57 years) were enrolled. The mean tumor diameter was 1.8 cm. Tumoricidal temperatures (>43 degrees C) were reached in 23 patients (92%). Tumor size was unchanged after thermotherapy (P = not significant). Pathologic necrosis was achieved in 17 (68%) patients. Complete necrosis of the invasive component was achieved in two patients. One hundred forty CEM is predictive of a 50% tumor response, and 210 CEM is predictive of a 100% tumor response (P =.003). Univariate linear regression predicts that peak tumor temperatures of 47.4 degrees C and 49.7 degrees C cause a 50% tumor response and a 100% tumor response, respectively.

CONCLUSIONS

Thermotherapy causes tumor necrosis and can be performed safely with minimal morbidity. The degree of tumor necrosis is a function of the thermal dose. Future studies will evaluate the impact of high doses of thermotherapy on margin status and complete tumor ablation.

Focused microwave phased array thermotherapy for primary breast cancer

BACKGROUND

A pilot safety study of focused microwave phased array thermotherapy in the treatment of primary breast carcinomas was conducted.

METHODS

Ten patients with breast carcinomas beneath the skin surface that ranged in maximal clinical size from 1 to 8 cm (mean, 4.3 cm) were treated with the breast compressed in the prone position. We planned to deliver a tumor thermal dose equivalent to 60 minutes at 43 degrees C. Breast imaging and pathology data were used to assess efficacy.

RESULTS

For the 10 patients, the mean tumor equivalent thermal dose was 51.7 minutes, the mean peak tumor temperature was 44.9 degrees C, and the mean treatment time was 34.7 minutes. Ultrasound imaging demonstrated a significant reduction in tumor size (mean, 41%) 5 to 18 days after thermotherapy in 6 (60%) of 10 patients. A significant tumor response on the basis of reduction in tumor size or significant tumor cell kill occurred in 8 (80%) of 10 patients.

CONCLUSIONS

With sufficient skin cooling, delivery of focused microwave phased array thermotherapy is safe in treating breast carcinomas when used alone, and some potential efficacy was demonstrated at the tumor thermal doses administered. Increased tumor thermal dose efficacy studies in larger patient populations for improved breast conservation should be investigated.

Hyperthermia for rectal cancer

BACKGROUND

In order to improve the clinical results of rectal cancer, hyperthermia has been prescribed in combination with chemotherapy and radiotherapy. The techniques of hyperthermia and their clinical applications to rectal cancer were reviewed.

METHODS

The development of heating devices has been intensively investigated, including external heating devices, intraluminal heating devices, circulation of warmed saline solution, and whole body hyperthermia.

RESULTS

Nonrandomized and randomized trials for rectal cancer have demonstrated an improved local response with the combined use of hyperthermia and conventional treatments. A preoperative therapy with hyperthermia increased resectability and decreased local recurrence, resulting in the improvement of the postoperative prognosis. There were no major postoperative complications related to the preoperative treatment. A lower incidence of local recurrence was observed in groups that underwent intra- or postoperative hyperthermia treatment, as compared with control groups. In cases with unresectable or local recurrent rectal cancer, hyperthermia achieved a local tumor regression and prolonged pain relief.

CONCLUSIONS

These clinical data suggest that hyperthermia combined with radiation or chemotherapy demonstrates great promise for the treatment of patients with carcinoma of the rectum.

For the clinical application of thermochemotherapy given at mild temperatures

It has been demonstrated in vitro and in vivo that hyperthermia can enhance the cytotoxicity of some chemotherapeutic agents. This paper summarizes the authors' own laboratory studies on the effect of chemotherapeutic agents given at elevated temperatures, experimental results obtained using animal tumour systems in other laboratories, and clinical trials of thermochemotherapy reported in literature. The in vivo studies have demonstrated that the thermal enhancement of cytotoxicity of many chemotherapeutic agents is maximized at mild temperatures such as at 40.5-43 degrees C. Comparison of in vitro and in vivo results using five agents show that the in vivo thermal enhancement increases with an increase in the activation energy obtained in the temperature range between 40.5 and 43.0 degrees C. A summary of experimental results obtained by various investigators indicates a potentially wide variation in the thermal enhancement of a given agent among the different types of tumours and suggests potential agents useful at moderately elevated temperatures. In vivo studies on nine different agents indicate that the drug(s) of choice at physiological temperatures may not be the drug(s) of choice at elevated temperatures. It is also shown that drug concentration in the target must be high for sufficient thermal enhancement. Clinical trials of thermochemotherapy have employed various heating methods, including local heating, hyerthermic perfusion and whole body hyperthermia. Extensive trials have been made in the treatment of melanoma and soft tissue sarcoma in the extremity. Hyperthermic isolated perfusion with chemotherapeutic(s) provides much higher drug concentration than a systemic drug administration in the target(s), resulting in a high tumour response rate and an increased survival of the patients. It is of interest that the most successful agent used in the treatment of both melanomas and sarcomas is melphalan and is the drug of choice at moderately elevated temperatures among the nine agents tested in the in vivo studies. Current results using the tumour necrosis factor with melphalan are impressive. In several institutes, techniques have been developed to uniformly heat the localized tumour, but studies are needed to find an agent effective at elevated temperatures to each type of tumours and to establish the methods for obtaining a sufficient drug concentration in the target tissue.

An adaptive microwave phased array for targeted heating of deep tumours in intact breast: animal study results

It has previously been reported in phantoms, that an adaptive radiofrequency phased array can generate deep focused heating distributions without overheating the skin and superficial healthy tissues. The present study involves adaptive microwave phased array hyperthermia tests in animals (rabbits) with and without tumours. The design of the adaptive phased array as applied to the treatment of tumours in intact breast, is described. The adaptive phased array concept uses breast compression and dual-opposing 915 MHz air-cooled waveguide applicators with electronic phase shifters and electric-field feedback, to focus automatically by computer control the microwave radiation in deep tissue. Temperature measurements for a clinical adaptive phased array hyperthermia system demonstrate tissue heating at depth with reduced skin heating.