Microwave-induced hyperthermia and radiotherapy in human superficial tumours: clinical results with a comparative study of combined treatment versus radiotherapy alone

A randomized phase-II study of reirradiation and hyperthermia versus reirradiation and hyperthermia plus chemotherapy for locally recurrent breast cancer in previously irradiated area

BACKGROUND

In patients with inoperable local regional recurrences of breast cancer in previously irradiated areas, local control is difficult to maintain and treatment options are limited. The Dutch standard treatment for such recurrences is reirradiation combined with hyperthermia. Apart from enhancing the effect of reirradiation, hyperthermia is also known to improve local effects of chemotherapy like cisplatin. This randomized phase-II trial compares reirradiation and hyperthermia versus the same treatment combined with cisplatin.

PATIENTS AND METHODS

From December 2010 up to January 2019, 49 patients were randomized, 27 in the standard arm and 22 in the combined arm. A total of 32 Gy was given in eight fractions of 4 Gy in 4 weeks, at two fractions per week. After January 2015, the radiation schedule was changed to 46 Gy in 23 fractions of 2 Gy, at five fractions per week. Hyperthermia was added once a week after radiotherapy. The combined arm was treated with four cycles of weekly cisplatin 40 mg/m².

RESULTS

Complete response rate was 60.9% in the standard arm and 61.1% in the combined arm (p = 0.87). Partial response rate was 30.4% in the standard arm and 33.3% in the combined arm (p = 0.79). One-year overall survival was 63.4% in the standard arm and 57.4% in the combined arm. One-year local progression-free interval was 81.5% in the standard arm and 88.1% in the combined arm (p = 0.95). Twenty-five percentage of patients in the standard arm experienced grade 3 or 4 acute toxicity and 29% of patients in the combined arm (p = 0.79).

CONCLUSION

No potential benefit could be detected of adding cisplatin to reirradiation and hyperthermia in patients with recurrent breast cancer in a previously irradiated area. With or without cisplatin, most patients had subsequent local control until last follow-up or death.

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.

The Effect of the Time Interval Between Radiation and Hyperthermia on Clinical Outcome in 400 Locally Advanced Cervical Carcinoma Patients

Background: Addition of deep hyperthermia to radiotherapy results in improved local control (LC) and overall survival compared to radiotherapy alone in cervical carcinoma patients. Based on preclinical data, the time interval between radiotherapy, and hyperthermia is expected to influence treatment outcome. Clinical studies addressing the effect of time interval are sparse. The repercussions for clinical applications are substantial, as the time between radiotherapy and hyperthermia should be kept as short as possible. In this study, we therefore investigated the effect of the time interval between radiotherapy and hyperthermia on treatment outcome. Methods: We analyzed all primary cervical carcinoma patients treated between 1996 and 2016 with thermoradiotherapy at our institute. Data on patients, tumors and treatments were collected, including the thermal dose parameters TRISE and CEM43T90. Follow-up data on tumor status and survival as well as late toxicity were collected. Data was analyzed using Cox proportional hazards analysis and Kaplan Meier analysis. Results: 400 patients were included. Kaplan Meier and univariate Cox analysis showed no effect of the time interval (range 30-230 min) on any clinical outcome measure. Besides known prognostic factors, thermal dose parameters TRISE and CEM43T90 had a significant effect on LC. In multivariate analysis, the thermal dose parameter TRISE (HR 0.649; 95% CI 0.501-0.840) and the use of image guided brachytherapy (HR 0.432; 95% CI 0.214-0.972), but not the time interval, were significant predictors of LC and disease specific survival. Conclusions: The time interval between radiotherapy and hyperthermia, up to 4 h, has no effect on clinical outcome. These results are re-ensuring for our current practice of delivering hyperthermia within maximal 4 h after radiotherapy.

Temperature and thermal dose during radiotherapy and hyperthermia for recurrent breast cancer are related to clinical outcome and thermal toxicity: a systematic review

Objective: Hyperthermia therapy (HT), heating tumors to 40-45 °C, is a known radiotherapy (RT) and chemotherapy sensitizer. The additional benefit of HT to RT for recurrent breast cancer has been proven in multiple randomized trials. However, published outcome after RT + HT varies widely. We performed a systematic review to investigate whether there is a relationship between achieved HT dose and clinical outcome and thermal toxicity for patients with recurrent breast cancer treated with RT + HT. Method: Four databases, EMBASE, PubMed, Cochrane library and clinicaltrials.gov, were searched with the terms breast, radiotherapy, hyperthermia therapy and their synonyms. Final search was performed on 3 April 2019. Twenty-two articles were included in the systematic review, reporting on 2330 patients with breast cancer treated with RT + HT. Results: Thirty-two HT parameters were tested for a relationship with clinical outcome. In studies reporting a relationship, the relationship was significant for complete response in 10/15 studies, in 10/13 studies for duration of local control, in 2/2 studies for overall survival and in 7/11 studies for thermal toxicity. Patients who received high thermal dose had on average 34% (range 27%-53%) more complete responses than patients who received low thermal dose. Patients who achieved higher HT parameters had increased odds/probability on improved clinical outcome and on thermal toxicity. Conclusion: Temperature and thermal dose during HT had significant influence on complete response, duration of local control, overall survival and thermal toxicity of patients with recurrent breast cancer treated with RT + HT. Higher temperature and thermal dose improved outcome, while higher maximum temperature increased incidence of thermal toxicity.

Results of Hyperthermia, Alone or Combined with Irradiation, in Chest Wall Recurrences of Breast Cancer

In the period between September 1983 and July 1987, 28 loco-regional recurrences (about 86% in the chest wall) of breast cancer in 19 patients were treated with external microwave hyperthermia. Of these, 11 lesions were treated with hyperthermia alone and 17 with the combination of heat and external irradiation. Hyperthermia was induced in most cases with 915 MHz microwave (at least 42 °C for 30–45 min, for 6–10 sessions). Radiation was administered using photon or electron beams with total doses varying from 2000 to 5000 cGy. Complete and partial response rates on the whole series of patients were 53.6% and 42.9%, respectively. Of 17 lesions treated with combined treatment, 10 had a complete (58.8%) and 7 a partial response; of 11 lesions treated with hyperthermia alone, 5 had a complete (45.5%), 5 a partial (45.5%), and 1 no response. Complete responses were long lasting in all but 3 cases, which recurred after 4 months (2 cases) and 1 year, respectively.

Evaluating Radiation in Combination with Hyperthermia Trials: The Importance of Clinical and Technical Parameters

A proper evaluation of hyperthermia and irradiation trials Is necessary to correctly interpret clinical results and to define limitations and properties of this new therapeutic approach. A better understanding of the « weight » of different technologic and clinical parameters that influence clinical response is thus clearly needed, particularly if future advances in hyperthermia technology and clinical results are to be expected. Patient variables, tumor variables, and treatment characteristics have been analyzed, and the difficulties of properly evaluating the « weight » of single parameters have been stressed. At the current state of knowledge, the Karnofsky index, site of disease (for regional heating), tumor status (recurrent versus metastatic disease) and XRT dose per fraction (for melanomas) seem to correlate with response. Tumor dimension, XRT total dose and thermal parameters reflecting the lowest tumor temperatures appear to statistically influence complete response rates of heated and irradiated tumors. In addition, a critical method of presenting results should be followed to enable comparison of data from different trials.

Experimental Investigation of Magnetic Nanoparticle-Enhanced Microwave Hyperthermia

The objective of this study was to evaluate microwave heating enhancements offered by iron/iron oxide nanoparticles dispersed within tissue-mimicking media for improving efficacy of microwave thermal therapy. The following dopamine-coated magnetic nanoparticles (MNPs) were considered: 10 and 20 nm diameter spherical core/shell Fe/Fe₃O₄, 20 nm edge-length cubic Fe₃O₄, and 45 nm edge-length/10 nm height hexagonal Fe₃O₄. Microwave heating enhancements were experimentally measured with MNPs dissolved in an agar phantom, placed within a rectangular waveguide. Effects of MNP concentration (2.5-20 mg/mL) and microwave frequency (2.0, 2.45 and 2.6 GHz) were evaluated. Further tests with 10 and 20 nm diameter spherical MNPs dispersed within a two-compartment tissue-mimicking phantom were performed with an interstitial dipole antenna radiating 15 W power at 2.45 GHz. Microwave heating of 5 mg/mL MNP-agar phantom mixtures with 10 and 20 nm spherical, and hexagonal MNPs in a waveguide yielded heating rates of 0.78 ± 0.02 °C/s, 0.72 ± 0.01 °C/s and 0.51 ± 0.03 °C/s, respectively, compared to 0.5 ± 0.1 °C/s for control. Greater heating enhancements were observed at 2.0 GHz compared to 2.45 and 2.6 GHz. Heating experiments in two-compartment phantoms with an interstitial dipole antenna demonstrated potential for extending the radial extent of therapeutic heating with 10 and 20 nm diameter spherical MNPs, compared to homogeneous phantoms (i.e., without MNPs). Of the MNPs considered in this study, spherical Fe/Fe₃O₄ nanoparticles offer the greatest heating enhancement when exposed to microwave radiation. These nanoparticles show strong potential for enhancing the rate of heating and radial extent of heating during microwave hyperthermia and ablation procedures.

A short time interval between radiotherapy and hyperthermia reduces in-field recurrence and mortality in women with advanced cervical cancer

Background

Combined radiotherapy and hyperthermia is a well-established alternative to chemoradiotherapy for advanced stage cervical cancer patients with a contraindication for chemotherapy. Pre-clinical evidence suggests that the radiosensitizing effect of hyperthermia decreases substantially for time intervals between radiotherapy and hyperthermia as short as 1–2 h, but clinical evidence is limited. The purpose of this study is to determine the effect of the time interval between external beam radiotherapy (EBRT) and same-day hyperthermia on in-field recurrence rate, overall survival and late toxicity in women with advanced stage cervical cancer.

Methods

Patients with advanced stage cervical cancer who underwent a full-course of curative daily EBRT and (4–5) weekly hyperthermia sessions between 1999 and 2014 were included for retrospective analysis. The mean time interval between EBRT fractions and same-day hyperthermia was calculated for each patient; the median thereof was used to divide the cohort in a ‘short’ and ‘long’ time-interval group. Kaplan-Meier analysis and stepwise Cox regression were used to compare the in-field recurrence and overall survival. Finally, high-grade (≥3) late toxicity was compared across time-interval groups. DNA repair suppression is an important hyperthermia mechanism, DNA damage repair kinetics were therefore studied in patient biopsies to support clinical findings.

Results

Included were 58 patients. The 3-year in field recurrence rate was 18% and 53% in the short (≤79.2 min) and long (>79.2 min) time-interval group, respectively (p = 0.021); the 5-year overall survival was 52% and 17% respectively (p = 0.015). Differences between time-interval groups remained significant for both in-field recurrence (HR = 7.7, p = 0.007) and overall survival (HR = 2.3, p = 0.012) in multivariable Cox regression. No difference in toxicity was observed (p = 1.00), with only 6 and 5 events in the short and long group, respectively. The majority of DNA damage was repaired within 2 h, potentially explaining a reduced effectiveness of hyperthermia for long time intervals.

Conclusions

A short time interval between EBRT and hyperthermia is associated with a lower risk of in-field recurrence and a better overall survival. There was no evidence for difference in late toxicity.

Hyperthermia and Radiation Therapy in Locoregional Recurrent Breast Cancers: A Systematic Review and Meta-analysis

PURPOSE

To conduct a systematic review and meta-analysis to evaluate the outcome of hyperthermia (HT) and radiation therapy (RT) in locally recurrent breast cancers (LRBCs).

METHODS AND MATERIALS

A total of 708 abstracts were screened from 8 databases according to the PRISMA guidelines. Single-arm and 2-arm studies, treating LRBCs with HT and RT but without surgery (for local recurrence) or concurrent chemotherapy were considered. The evaluated endpoint was complete response (CR).

RESULTS

Thirty-one full text articles, pertaining to 34 studies, were shortlisted for the meta-analysis. Eight were 2-arm (randomized, n=5; nonrandomized, n=3), whereas 26 were single-arm studies. In all, 627 patients were enrolled in 2-arm and 1483 in single-arm studies. Patients were treated with a median of 7 HT sessions, and an average temperature of 42.5°C was attained. Mean RT dose was 38.2 Gy (range, 26-60 Gy). Hyperthermia was most frequently applied after RT. In the 2-arm studies, a CR of 60.2% was achieved with RT + HT versus 38.1% with RT alone (odds ratio 2.64, 95% confidence interval [CI] 1.66-4.18, P<.0001). Risk ratio and risk difference were 1.57 (95% CI 1.25-1.96, P<.0001) and 0.22 (95% CI 0.11-0.33, P<.0001), respectively. In 26 single-arm studies, RT + HT attained a CR of 63.4% (event rate 0.62, 95% CI 0.57-0.66). Moreover, 779 patients had been previously irradiated (696 from single-arm and 83 from 2-arm studies). A CR of 66.6% (event rate 0.64, 95% CI 0.58-0.70) was achieved with HT and reirradiation (mean ± SD dose: 36.7 ± 7.7 Gy). Mean acute and late grade 3/4 toxicities with RT + HT were 14.4% and 5.2%, respectively.

CONCLUSIONS

Thermoradiation therapy enhances the likelihood of CR rates in LRBCs over RT alone by 22% with minimal acute and late morbidities. For even those previously irradiated, reirradiation with HT provides locoregional control in two-thirds of the patients. Thermoradiation therapy could therefore be considered as an effective and safe palliative treatment option for LRBCs.

Hyperthermia Is Now Included in the NCCN Clinical Practice Guidelines for Breast Cancer Recurrences: An Analysis of Existing Data

BACKGROUND

Hyperthermia has been included in the 2013 National Comprehensive Cancer Network (NCCN) guidelines as an option for the treatment of breast recurrences. The purpose of this article is to demonstrate the important role of hyperthermia as a therapeutic modality by presenting clinical trials on this subject carried out in the last decades.

MATERIALS AND METHODS

All relevant trials published since 1987 were retrieved from Medline and reviewed.

RESULTS

Results show that the addition of hyperthermia to radiotherapy and/or chemotherapy for the treatment of breast cancer enhances treatment response and can increase local control.

CONCLUSION

Further studies are required to evaluate potential benefits of hyperthermia in the treatment of other kinds of superficial tumors.

Comparison of magnetic nanoparticle and microwave hyperthermia cancer treatment methodology and treatment effect in a rodent breast cancer model

PURPOSE

The purpose of this study was to compare the efficacy of iron oxide/magnetic nanoparticle hyperthermia (mNPH) and 915 MHz microwave hyperthermia at the same thermal dose in a mouse mammary adenocarcinoma model.

MATERIALS AND METHODS

A thermal dose equivalent to 60 min at 43 °C (CEM60) was delivered to a syngeneic mouse mammary adenocarcinoma flank tumour (MTGB) via mNPH or locally delivered 915 MHz microwaves. mNPH was generated with ferromagnetic, hydroxyethyl starch-coated magnetic nanoparticles. Following mNP delivery, the mouse/tumour was exposed to an alternating magnetic field (AMF). The microwave hyperthermia treatment was delivered by a 915 MHz microwave surface applicator. Time required for the tumour to reach three times the treatment volume was used as the primary study endpoint. Acute pathological effects of the treatments were determined using conventional histopathological techniques.

RESULTS

Locally delivered mNPH resulted in a modest improvement in treatment efficacy as compared to microwave hyperthermia (p = 0.09) when prescribed to the same thermal dose. Tumours treated with mNPH also demonstrated reduced peritumoral normal tissue damage.

CONCLUSIONS

Our results demonstrate similar tumour treatment efficacy when tumour heating is delivered by locally delivered mNPs and 915 MHz microwaves at the same measured thermal dose. However, mNPH treatments did not result in the same type or level of peritumoral damage seen with the microwave hyperthermia treatments. These data suggest that mNP hyperthermia is capable of improving the therapeutic ratio for locally delivered tumour hyperthermia. These results further indicate that this improvement is due to improved heat localisation in the tumour.

Hyperthermia induced NFkappaB mediated apoptosis in normal human monocytes

Conceptual approaches of heat-induced cytotoxic effects against tumor cells must address factors affecting therapeutic index, i.e., the relative toxicity for neoplastic versus normal tissues. Accordingly, we investigated the effect of hyperthermia treatment (HT) on the induction of DNA fragmentation, apoptosis, cell-cycle distribution, NFkappaB mRNA expression, DNA-binding activity, and phosphorylation of IkappaBalpha in the normal human Mono Mac 6 (MM6) cells. For HT, cells were exposed to 43 degrees C. FACS analysis showed a 48.5% increase in apoptosis, increased S-phase fraction, and reduced G2 phase fraction after 43 degrees C treatments. EMSA analysis showed a dose-dependent inhibition of NFkappaB DNA-binding activity after HT. This HT-mediated inhibition of NFkappaB was persistent even after 48 h. Immunoblotting analysis revealed dose-dependent inhibition of IkappaBalpha phosphorylation. Similarly, RPA analysis showed that HT persistently inhibits NFkappaB mRNA. These results demonstrate that apoptosis upon HT exposure of MM6 cells is regulated by IkappaBalpha phosphorylation mediated suppression of NFkappaB.

Superficial hyperthermia and irradiation for recurrent breast carcinoma of the chest wall: prognostic factors in 196 tumors

PURPOSE

To correlate patient-, tumor-, and treatment-related factors with subsequent local tumor control.

METHODS AND MATERIALS

From 1977 to 1990, 196 subcutaneous/superficial lesions (179 measurable, 17 microscopic) in 151 patients with recurrent breast carcinoma of the chest wall were treated with superficial 915-MHz microwave hyperthermia and irradiation. The definition of min t43 > or = 10 min is that all monitored tumor catheters had a minimum of 1 hyperthermia session with temperatures > 43 degrees C for at least 10 min.

RESULTS

Factors correlating with local control on univariate analysis included length of survival (> or = 1 year vs. < 1 year) (p < 0.0001), specific absorption rate (SAR) (> or = 25% vs. < 25%) (p = 0.0001), minimum t43 > 10 min (p < 0.0001), tumor volume (p < 0.0001), tumor surface area (p < 0.0001), tumor depth (p = 0.0002), number of hyperthermia sessions (p = 0.0003), and current radiation dose (p = 0.0012). On multivariate analysis, the factors best correlated with ultimate local control were SAR (p < 0.001) and number of hyperthermia sessions (p = 0.003).

CONCLUSIONS

Multivariate analysis supports the importance of adequate specific absorption rate (SAR) coverage as a better predictor of local control than tumor volume, surface area, or depth. The explanation is that SAR can be correlated with the tumor surface area and depth, depending on the hyperthermia applicator characteristics. It is recommended that future clinical trials stratify study lesions into either SAR > or = 25% or < 25% because this can be readily estimated prior to initiating treatment. It is also recommended that future clinical trials attempt to have adequate lengths of follow-up after therapy to assess the results in long-term survivors.

Changes in muscle blood flow distribution during hyperthermia

Blood flow is a critical parameter for obtaining satisfactory temperature distributions during clinical hyperthermia. This study examines the changes in blood flow distribution in normal porcine skeletal muscle before, during and after a period of regional microwave hyperthermia. The baseline blood flow distribution during general anaesthesia and after the insertion of the thermal probes was established independently in order to isolate the changes due to hyperthermia. General anaesthesia alone and thermocouple insertion during anesthesia had no significant effect on the muscle blood flow distribution. Regional microwave heating generated a non-uniform blood flow distribution which was a function of the tissue temperature distribution. Blood flow was greater in those tissues samples in which higher temperatures were recorded and less in those sampled further from the applicators peak SAR (Specific Absorption Rate). The increase in blood flow appears to be primarily a local phenomenon. Although muscle blood flow may be considered to be uniform prior to heating, this does not hold during hyperthermia treatment. Therefore, the non-uniform nature of the blood distribution during heating should be incorporated into any practical bioheat transfer model.

Biological rationale and clinical experience with hyperthermia

Hyperthermia (HT) as an adjunct to radiation therapy (RT) has been a focus of interest in cancer management in recent years there have been numerous randomized and nonrandomized studies conducted to assess the efficacy of HT combined with either RT or chemotherapy especially in the treatment of superficially seated malignant tumors. The major impact of HT is currently on locoregional control of tumor. Heat may be directly cytotoxic to tumor cells or inhibit repair of both sublethal and potentially lethal damage after radiation. These effects are augmented by the physiological conditions in tumor that lead to states of acidosis and hypoxia. Blood flow is often impaired in tumor relative to normal tissues, and HT may lead to a further decrease in blood flow and augment heat sensitivity. Three major areas of clinical investigation have borne the greatest fruit for HT as adjunctive therapy to RT. These include recurrent and primary breast lesions, melanoma, and head and neck neoplasms. Thermal enhancement ratio was increased in all cases and is approximately 1.4 for neck nodes, 1.5 for breast, and 2 for malignant melanoma. In general, the most important prognostic factors for complete response (CR) are RT dose, tumor size and minimal thermal parameters minimal thermal dose (t43min), mean minimal temperature (Tmin) or T90, i.e., temperature exceeded by 90% of thermal sensors]. The number of HT fractions administered per week appears to have no bearing on the overall response, which may be indicative of the effects of thermotolerance. The total number of HT fractions delivered also appears irrelevant provided adequate HT is delivered in one or two sessions. The major prognostic factors for the duration of local control were tumor histology, concurrent RT dose, tumor depth and Tmin. Although numerous single institution studies showed increased CR rates and improved local control, the efficacy of HT as an adjunct to RT should be assessed with well-designed multi-institutional randomized clinical trials. Such clinical trials are underway.

Hyperthermia in the multimodal therapy of advanced rectal carcinomas

The synergistic effects of hyperthermia (raising temperatures to 40 degrees C and above) when combined with radiotherapy and cytotoxic drugs and a modulation of immunological phenomena have been demonstrated in the laboratory. Pre-clinical data relating to hyperthermia are summed up, along with their implications for clinical application. Controlled studies of local and regional hyperthermia have been performed during recent years, and these show us that the adjunction of hyperthermia provides at least an improvement of local control compared with radiotherapy alone. Current clinical results are summarized. Therapy systems based on radiowave irradiation have been commercially available for regional hyperthermia of the pelvis since the mid 1980s. This technology allows us to perform sufficiently tolerable and effective regional hyperthermia on rectal carcinomas. Used as part of curative preoperative and postoperative multimodal therapeutic strategies, hyperthermia can lead to improvement in local control (resectability, down-staging, progression-free time, recurrence rate), at least for certain risk groups. The preoperative radio-chemo-thermotherapy of advanced primary and recurring rectal carcinoma, uT3/4, was tested in a phase-I/II study of 20 patients. Therapy procedure, acute toxicity, thermal parameters, and response are described and discussed for this patient group. The regimen proved to be sufficiently tolerable, and complications did not occur. Tumor resection was performed on 14 of the 20 patients; 13 of the procedures were R0-resections and one was an R2 resection. In 64% of the resected rectal carcinomas, histopathological down-staging of the pretherapeutic endosonographical stadium was achieved; in three of the patients, despite continued non-resectability, local control has now been maintained for more than 12 months. In two patients with nonresectable rectal carcinomas, local progress was seen during the neoadjuvant combination therapy.

A pilot study of a new therapeutic approach in the treatment of locally advanced stages of rectal cancer: neoadjuvant radiation, chemotherapy and regional hyperthermia

The synergistic effects of hyperthermia (temperatures > or = 41 degrees C) when combined with radiotherapy or cytotoxic drugs, as well as a modulation of tumour-related immunological phenomena have been demonstrated preclinically. Local or regional hyperthermia in combination with radiation or chemotherapy has been studied in patients during recent years, and has convincingly demonstrated that hyperthermia is feasible and tolerated by patients. Furthermore, there is strong evidence that hyperthermia may provide an improvement in local control as compared with radiotherapy or chemotherapy alone. Systems based on radiowave irradiation allow sufficiently tolerable and effective regional hyperthermic therapy in patients with rectal carcinomas. Used as part of curative pre-operative and postoperative multimodal therapeutic strategies in high-risk patients with locally advanced rectal carcinomas, hyperthermia may result in improved local control and a higher rate of sphincter-sparing procedures. 20 patients with non-resectable, locally advanced primary or recurring rectal carcinoma T3/4 entered a phase I/II study of pre-operative radiochemothermotherapy with folinic acid and 5-fluorouracil, radiation (45 Gy HD), as well as regional hyperthermia once a week followed by chemotherapy after surgery. The regimen proved to be sufficiently tolerable. Acute grade III or IV toxicities did not occur after hyperthermia. Tumour resections were performed on 14 of the 20 patients, with 13 being complete. In 9 of the carcinomas, downstaging compared with the pretherapeutic stage was achieved. In 3 of 6 patients with persistent non-resectable tumours, local control has now been maintained for more than 12 months. One patient progressed locally during neoadjuvant combination therapy. These results prompted the initiation of a prospective randomised study to evaluate the relative importance of regional hyperthermia in this setting.

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.

Prognostic factors for tumour response and skin damage to combined radiotherapy and hyperthermia in superficial recurrent breast carcinomas

Prognostic factors for complete tumour response and acute skin damage to combined hyperthermia and radiotherapy were analysed in material of patients with breast cancer, recurrent in previously irradiated areas. Radiotherapy was given daily to a total absorbed dose of 30.0 Gy in 2 weeks or 34.5 Gy in 3 weeks. The first radiotherapy schedule was combined with heat twice weekly, a total of four heat treatments (schedule A). The second radiotherapy schedule was combined with heat either once or twice a week resulting in a total of three (schedule B) or six (schedule C) heat treatments. Heat was induced with microwaves (2450, 915 or 434 MHz) via external applicators and always given after the radiotherapy fraction. The complete response (CR) rate in evaluable patients was 71% (49/69). There was no significant difference in CR rate between the three different hyperthermia schedules. The CR rates were 74% (14/19), 65% (15/23) and 74% (20/27) for schedules A, B and C respectively. The only factor predicting CR, evaluated both uni- and multivariately, was the CRE-value for the present radiotherapy dose (p = 0.02). If only tumours treated with 915 MHz were taken into account, however, then the highest minimum temperature at a given heat session predicted complete response (p = 0.03). This was true also in a multivariate analysis of this subgroup of tumours. A Kaplan-Meier analysis (log rank test) showed no significant difference in duration of CR between the different treatment schedules. Cox's proportional hazards method revealed three significant factors: tumour size (negatively correlated, p = 0.007), the time interval between the diagnosis of the primary tumour and the present treatment (p = 0.02) and the average temperature (0.03). Maximum acute skin reactions in the treatment field were scored according to an ordinal scale of 0-8, modified after WHO 1979. Twenty-six treatment areas (32%) expressed more severe skin damage (score > or = 5) in terms of desquamation with blisters (14%) and necrosis or ulceration (19%). Factors correlated with skin damage were the size of the lesion area (p = 0.011), the highest average maximum temperature during a given heat session (p = 0.03) and the fractionation schedule of hyperthermia (p = 0.05). The extent of previous radiotherapy absorbed dose, previous surgery in the treated area or previous chemotherapy had no significant influence on the acute skin reactions.

Predictive factors for skin reactions in patients treated with thermoradiotherapy

In this study we performed univariate analyses to analyse the predictive factors for skin reactions, i.e. erythema, thermal blisters and ulceration, that occur during thermoradiotherapy. One hundred and twenty-six fields in 126 patients were treated with thermoradiotherapy using 915 MHz external microwave hyperthermia. Mean age of patients was 62 years. All but 11 lesions received previous therapy. Prior treatment included surgery (75%), chemotherapy (60%) and/or radiation therapy (51%). The mean previous radiation dose was 54 +/- 2 Gy. The concurrent tumour radiation dose was 45 +/- 1 Gy, in 16 fractions, over 35 elapsed days (dose per fraction of 1.6-4.8 Gy). The mean number of heat sessions administered was 5.5 +/- 0.2 (range 1-14). In 83% of cases hyperthermia was administered biweekly. Forty-two patients were treated without any skin reaction (33%), erythema occurred in 59 fields (47%), transient thermal blisters occurred in 25 fields (20%) and ulceration occurred in 23 fields (18%). In 25 cases, two or more skin reactions (20%) were observed concurrently. Concurrent radiation dose correlated with skin reactions (p = 0.02). The incidence of skin reactions was inversely correlated with previous radiation therapy (p = 0.04) and previous radiation therapy dose (p = 0.04) possibly due to fibrosis. None of the tumour or skin thermal parameters correlated with the reaction rate.

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 x 44 degrees C for 30 min) and megavoltage radiation (4 x 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.

A century with hyperthermic oncology in Scandinavia

The hyperthermic research during the last 100 years is reviewed with the aim to describe a research activity which has been performed in parallel to and associated with the development of radiation oncology. Basic and clinical research in several Scandinavian centres has made major international contributions to the establishment of a rationale for and implementation of hyperthermia as a combined modality treatment with chemotherapy or radiation in oncology. At the same time it has been demonstrated that collaboration and integration easily could be performed within the Scandinavian centres. Hyperthermic oncology is therefore a typical example of how research involving both biological, physical/engineering, and clinical skills in a proper environment can create valuable results.

A variable microwave array attenuator for use with single-element waveguide applicators

The effectiveness of hyperthermia treatments is often limited by temperature inhomogeneity that arises in the treatment field due to variable tissue properties and blood flow. Moreover, blood flow can change during a treatment, leading to the formation of hot and cool areas even if the initial temperature distribution is uniform. A variable microwave array attenuator has been constructed, that will enable the field patterns of single element microwave waveguide hyperthermia applicators to be altered during treatment, to improve temperature homogeneity. The coupling bolus was designed with an array of individually controlled elements, each filled with a microwave absorbing saline solution. Additions or withdrawals of saline are made to alter the power deposition in a specific area of the treatment field. Thermographic measurements were made in muscle equivalent phantom materials, with the bolus/waveguide assembly. Results showed that the variable array attenuator was able to significantly alter the heating pattern of a large waveguide applicator.

Thermoradiotherapy for superficial tumour deposits in the head and neck

Tumour deposits in the head and neck region were treated with hyperthermia using 915 MHz external microwave applicators and radiation therapy between 1986 and 1990. The mean (+/- SE) radiation dose was 47 +/- 2 Gy (range 21-77 Gy). All but four patients had failed previous therapy. Mean tumour volume was 40 +/- 10 cm3 (range 0.3-276 cm3). Hyperthermia was administered biweekly in 80% of the patients in 6.0 +/- 0.4 sessions (range 1-10); thermometry involved 3.6 +/- 0.4 catheters (range 1-9) and 5.7 +/- 0.4 sensors (range 1-12) per tumour. Of the 50 lesions evaluable for response, 29 had a complete response (58%), and 20 had a partial response (40%). Lesions were stratified by depth. In tumours considered potentially heatable (i.e. depth < or = 3 cm and lateral dimensions at least 2 cm less than boundary of applicator), the complete response rate was 81% (26/32, 47 +/- 2 Gy, 15 +/- 3 cm3); whereas for patients with tumours deeper than 3 cm, the complete response rate was 17% (3/18, 48 +/- 3 Gy, 110 +/- 21 cm3), p = 0.0001. Among lesions < or = 3 cm depth that exhibited a complete response, six recurred (24%, 5.8 +/- 1.8 months) while 20 lesions were recurrence free at last follow-up of 11.9 +/- 1.2 months). The overall survival of patients with lesions < or = 3 cm depth was 11.5 +/- 1.3 months (range 2.4-32.3 months) while for patients with lesions > 3 cm depth survival was 6.7 +/- 0.9 months (range 2.1-18.6 months), p = 0.01. In superficial lesions with depth < or = 3 cm, multivariate logistic regression analysis indicated that the model best correlating with complete response included radiation dose (p = 0.08) and tumour volume (p = 0.08, model p = 0.004). Multivariate proportional hazard analysis indicated that the model best correlating with duration of local control included tumour depth (p = 0.03) and previous radiation therapy (p = 0.08, model p = 0.006). Twenty-two fields were treated without any skin reactions (39%), 23 evidenced erythema (40%) and eight thermal blistering (14%). Ulceration occurred in 11 treatment fields but in all but one of these cases the ulceration may have been due to tumour breakdown as there was direct invasion of the skin by tumour prior to the initiation of treatment. The maximal skin temperature was the best predictor of morbidity although the correlation was not statistically significant (p = 0.19).

Thermoradiation therapy for superficial malignant tumors

BACKGROUND

Between 1980-1990, 126 patients were treated with radiation therapy (RT) and hyperthermia using 915-MHz external microwave applicators. All but 11 patients had failed to respond to previous therapy.

METHODS

The mean tumor volume was 73 +/- 13 cm3, and the mean radiation dose delivered was 45 +/- 1 Gy. Hyperthermia was administered biweekly in 83% of the fields in 5.5 +/- 0.2 sessions. Lesions were stratified by depth. The predictive influence of pretreatment or treatment parameters was analyzed for the probability of response by logistic regression and for the duration of local control by proportional hazards.

RESULTS

In tumors considered potentially heatable (i.e., < or = 3-cm deep), the complete response (CR) rate was 70%, whereas the CR rate for patients with tumors deeper than 3 cm was 18% (P < 0.0001). Among superficial lesions of less than or equal to 3-cm depth that exhibited a CR, 14 recurred (26%, 8.7 +/- 1.6 months), while 39 lesions were recurrence-free at last follow-up of 17.8 +/- 1.4 months. The 50% tumor-effective dose was 44 Gy. For superficial lesions that received between 30-60 Gy, the CR rate was 55% when the fraction size was less than 3 Gy, whereas it was 77% when the fraction size was 3-4 Gy (P = 0.05). Multivariate logistic regression analysis indicated that the model best correlating with CR included concurrent radiation dose (P = 0.006) and tumor volume (P = 0.02; model P = 0.0001). Multivariate proportional hazard analysis indicated that the model best correlating with duration of local control included tumor histology (P = 0.004; model P = 0.0007). The overall survival rate of patients with lesions of less than or equal to 3-cm depth who were treated with thermoradiation therapy was 16.1 +/- 1.2 months. For patients with lesions more than 3-cm deep, survival was 8.7 +/- 1.1 months (P < 0.001). Forty-two fields were treated without any skin reactions (33%), 59 exhibited erythema (47%), and 25 experienced thermal blistering (20%).

CONCLUSIONS

Treatment of superficial malignant tumors can benefit from the adjuvant use of hyperthermia delivered with external 915-MHz applicators provided tumors are less than 3 cm from the surface and the lateral margins are within the 50% specific absorption rate (SAR) on the surface.

Wound repair after fractionated external beam radiation therapy and concomitant hyperthermia in an experimental rat model

BACKGROUND

Fractionated radiation therapy (RT) with adjuvant hyperthermia (HT) is being used in the treatment of cancer with noted clinical success. However, little information regarding wound repair in tissues receiving this combination therapy is available for comparison of surgical risk. Consequently, this study was undertaken to assess the effects of this combined therapy on wound healing by quantitatively evaluating wound repair using tensile strength measurements.

METHODS

Four treatment cohorts were designated: sham control, RT alone (600 cGy/d for 4 days), HT alone (water bath at 41.8 degrees C, subcutaneous temperature of 41.0 +/- 0.5 degrees C for 60 minutes on days 1 and 4), and combined RT and HT. At 1 week after treatment, surgical incisions of the dorsal flank were made. Tensile strength measurements of wounds were obtained at 14 and 21 days after incision.

RESULTS

No significant differences were observed in the combined treatment arm (RT and HT) compared with the reduced wound breaking strength of RT alone. Statistically significant differences in tensile strength were seen when the control group or HT alone was compared with RT and HT or RT alone.

CONCLUSIONS

Concomitant exposure to fractionated RT and specific HT conditions demonstrated no disproportionate alteration in wound tensile strength compared with radiation exposure alone in this animal model.

On-line monitoring of ultrasonic surgery with MR imaging

Ultrasonic surgery was performed in rabbits and dogs under the guidance of magnetic resonance (MR) imaging. Two different MR techniques were used to guide the ultrasound beam. T2-weighted images showed lesion formation within a few minutes after sonication. T1-weighted GRASS (gradient-recalled acquisition in the steady state) images were sensitive to temperature elevations, permitting monitoring of lesion creation with MR imaging. Short TR T1-weighted GRASS images were not as helpful in detecting temperature elevation because of a reduction in signal-to-noise ratio. T2-weighted fast spin-echo images were compared with conventional T2-weighted spin-echo images. The former produced high-quality images in a fraction of the imaging time. This study shows that it is possible to monitor and guide ultrasonic surgery with MR imaging.

Local hyperthermia, radiation therapy, and chemotherapy in patients with local-regional recurrence of breast carcinoma

We retrospectively reviewed the response rate and the acute and long-term toxicity of combined treatment using radiation therapy, hyperthermia, and chemotherapy in 29 patients with locally or regionally recurrent or advanced adenocarcinoma of the breast who completed at least 4 of the 6 prescribed hyperthermia treatments as part of a Phase I-II trial. Thirty-nine separate hyperthermia treatment fields were evaluated. Cisplatin alone or cisplatin with etanidazole or bleomycin was delivered just prior to hyperthermia once weekly. Hyperthermia was delivered to a target minimum tumor temperature of 43 degrees C +/- 0.5 for 60 min. Following hyperthermia, a 400 cGy fraction of radiation was given. The radiation fraction size on other days was 200 cGy. Twenty-two fields had previously been irradiated and 17 fields had not. Prior chemotherapy had been given in 24 of 29 patients (83%) and hormonal therapy given in 21 (72%). The median follow-up time is 10 months; 16/29 patients (55%) have died of disease. The overall complete response rate for all fields was 53%. Response rate was not related to any clinical factor, radiation dose, microwave or ultrasound technique, type of chemotherapy, or tumor temperatures, but the number of patients in the study population was small. A statistically significant association between the likelihood of complications and the total radiation therapy dose (previous radiation and present radiation) was found. Persistent ulceration lasting greater than 1 month after completing treatment was seen in 67% of previously irradiated fields compared to 21% of fields that had not been previously treated (p = 0.015). Surgical wound repair was needed for 38% of fields with a history of prior irradiation versus 6% of those without prior treatment (p = 0.050). A statistically significant radiation therapy dose response was found for the likelihood of these complications. None of the hyperthermia temperature parameters studied correlated with an increased risk of complication. We conclude that the combination of radiation therapy, hyperthermia, and chemotherapy results in a high rate of complete response. However, in patients who have been treated with prior radiation therapy, this combination may be more locally toxic than treatment with hyperthermia and radiation therapy alone. The precise impact of chemotherapy on the therapeutic index of hyperthermia and radiation therapy remains to be determined in randomized clinical trials.

Quantitative assessment of impedance tomography for temperature measurements in hyperthermia

The objective of this study is a non-invasive assessment of the thermal dose in hyperthermia. Electrical impedance tomography (EIT) has previously been given a first trial as a temperature monitoring method together with microwave-induced hyperthermia treatment, but it has not been thoroughly investigated. In the present work we have examined this method in order to investigate the correlation in vitro between the true spatial temperature distribution and the corresponding measured relative resistivity changes. Different hyperthermia techniques, such as interstitial water tubings, microwave-induced, laser-induced and ferromagnetic seeds have been used. The results show that it is possible to find a correlation between the measured temperature values and the tomographically measured relative resistivity changes in tissue-equivalent phantoms. But the uncertainty of the temperature coefficients, which has been observed, shows that the method has to be improved before it can be applied to clinical in vivo applications.

Parameters predictive for complications of treatment with combined hyperthermia and radiation therapy

Pretreatment and treatment related factors were reviewed for 996 hyperthermia sessions involving 268 separate treatment fields in 131 patients managed with hyperthermia for biopsy confirmed local-regionally advanced or recurrent malignancies to ascertain parameters associated with the development of complications. A subset of 249 fields were identified in which multipoint or mapped temperature data were available for at least one treatment session per field. A total of 198 fields involved superficially located tumors (less than or equal to 3 cm from the surface), whereas 51 fields involved more deeply located tumors. Most of these patients had received extensive prior therapy: 77% had surgery, 75% chemotherapy, 65% radiation therapy and 28% hormonal therapy. They were treated with hyperthermia in conjunction with radiation therapy (244 fields) or hyperthermia alone (5 fields). The hyperthermia treatment objectives were to elevate intratumoral temperatures to a minimum of 43.0 degrees C for 45 minutes while maintaining maximum normal tissue temperatures to less than or equal to 43 degrees C and maximum intratumoral temperatures to less than or equal to 50 degrees C. The hyperthermia was given within 30 to 60 minutes following radiation therapy without the administration of additional analgesics. Hyperthermia treatment regimens using radiative electromagnetic, ultrasound, or radiofrequency interstitial techniques were individualized, with 3 to 4 days between hyperthermia treatments and an average of 3.6 treatments (range 1-14; standard deviation 2.2) utilized per field. A total of 38 complications in 33 treatment fields were noted; an incidence of 27/198 (13.6%) for fields with superficially located tumors, and 6/51 (11.8%) in fields with more deeply located tumors. Univariate analyses demonstrated statistically significant correlations between the maximum tumor temperature (p = 0.0005), average of the maximum tumor temperatures (p = 0.0006), the average of the % tumor temperatures greater than 43.5 degrees C (p = 0.0071), and the average number of hyperthermia treatments (p = 0.033), with the development of complications. The average of the maximum measured tumor temperature for fields without complications was 44.6 degrees C compared with 45.9 degrees C for fields with complications. The complication rate increased from 7.5% (9/120) in fields that received one or two hyperthermia treatments to 18.6% (24/129) in fields that received greater than two hyperthermia treatments. Multivariate logistic regression analyses revealed the best bivariate model predictive of the development of complications included average of the maximum tumor temperature and the number of treatments per field (p = 0.00012 for the bivariate model).(ABSTRACT TRUNCATED AT 400 WORDS)

Changes in temperatures and thermal doses with fraction number during hyperthermic treatment of locally advanced breast carcinoma

Seventeen patients with locally advanced breast cancer were given hyperthermic treatment, and changes in temperatures and thermal doses with fraction number were studied. The changes were related to the vascular density of the treated volume before treatment. Multi-point thermistor probes were used for temperature measurements. Two parameters were determined for each probe location, a steady-state temperature, Ts, and a thermal dose, t43. To quantify changes in Ts and t43, linear curves were fitted to plots of these temperature parameters versus fraction number. The slopes of the curves, kTs and kt43, were used to represent the changes in Ts and t43, respectively. Vascular density was determined by histological analysis of biopsies taken from the temperature probe locations before the first heat treatment. Generally, Ts and t43 increased with increasing fraction number. kTs and kt43 were positively correlated to the vascular density of the normal tissue in the treatment volume, i.e. the increase in Ts and t43 was largest in the best-vascularized tissue. The cooling capacity of the normal tissue was probably reduced during the later heat fractions, either because of direct damage to the blood vessels or because of an impaired thermoregulative response. No relationship was found between the temperature parameters and the vascularization of the malignant tissue in the treatment volume. The present results show that the use of a fractionated schedule for heat treatment of locally advanced breast carcinoma may increase the temperatures and thermal doses achieved during treatment. A more uniform heating of the tumours can therefore be achieved by giving multiple heat fractions in the tumour areas that are difficult to heat adequately in one session.

Hyperthermia and radiation therapy of local-regional recurrent breast cancer: prognostic factors for response and local control of diffuse or nodular tumors

Over the past decade, hyperthermia has been extensively studied as an adjuvant to radiation therapy in the management of local-regional metastases from adenocarcinoma of the breast. A retrospective review of our experience from July 1982 to January 1990 identified 241 fields in 89 patients which satisfied the following criteria: biopsy confirmation of recurrent or metastatic adenocarcinoma of the breast; involvement of the chest wall and/or regional lymph nodes with diffuse or nodular metastases; treatment which included radiation therapy and externally administered hyperthermia during which mechanically-mapped and/or multipoint normal tissue and intratumoral temperatures were monitored; and at least one follow-up evaluation at 3 weeks or more after completion of treatment. The majority of fields were in patients who had extensive prior treatment including radiation therapy (68%), chemotherapy (86%), and hormonal therapy (58%). Treatment consisted of radiation therapy (average dose: 39.88 Gy) and hyperthermia (1-12 treatments; average 3.12); concurrent chemotherapy or hormonal therapy were also administered in 3% and 32% of the fields, respectively. Parameters characterizing the initial breast cancer, the patient and tumor at the time of hyperthermia, and the treatment were studied in univariate and multivariate analyses with complete response rate at the time of maximum tumor regression and duration of local control as endpoints. The treatments were well tolerated with no life-threatening complications noted. The means for all fields of the mean minimum, mean maximum, and mean average measured intratumoral temperatures were 40.3 degrees C, 44.6 degrees C, and 42.4 degrees C, respectively. At 3 weeks following completion of radiation therapy, response rates were: complete response (52%), partial response (8%), no response (17%), and continuing regression (monotonic regression to less than 50% of initial volume) was noted in 22% of the fields. At the time of maximum tumor regression local control was noted in 72% of the fields. Five parameters correlated with higher complete response in univariate and multivariate analysis: lower T-stage of the initial breast cancer; at the time of hyperthermia age less than 50 years, Karnofsky status greater than 95%, and the absence of distant metastases; and the use of concurrent hormonal therapy. The absence of a family history of breast cancer and concurrent radiation dose greater than or equal to 25 Gy significantly correlated with higher complete response in the univariate but not in the best multivariate models.(ABSTRACT TRUNCATED AT 400 WORDS)

Superficial microwave-induced hyperthermia in the treatment of chest wall recurrences in breast cancer

Our study concerns 42 patients with chest wall recurrences from breast cancer: 17 Stage 1 (less than 4 cm in diameter), 11 Stage 2 (more than 4 cm), seven Stage 3 (skin ulceration whatever tumor size), and seven Stage 4 (neoplastic lymphangitis and/or skin nodules covering chest wall beyond midline). All the patients were treated with 2450 MHz microwaves by means of a generator with 4 magnetrons (250 to 300 W) and arterial applicators delivering 5 to 10 W/cm2. Each applicator is coupled with an infrared thermometer allowing an atraumatic temperature control processed by a PC-compatible computer using a Turbo Pascal program. A temperature of 41.5 degrees C to 42.5 degrees C was maintained for 45 minutes from the skin surface to a 2.5-cm depth within tissues. Hyperthermia alone was done in four patients; hyperthermia was combined with chemotherapy in four patients, and with electrontherapy (2 X 450 cGy or 3 X 350 cGy/week) in 34 patients: tumor dose under 3000 cGy in seven patients and over 3000 cGy in 27 patients. We observed a complete response in 22 patients (52.3%), a partial response (greater than 50%) in 11 patients (26.1%), and no response in nine patients (21.4%). No complete response was observed in patients treated with hyperthermia alone or in conjunction with chemotherapy. The local control was demonstrated to be improved only in patients treated with hyperthermia and radiotherapy. The results were correlated with tumor stage: ten complete responses out of 12 Stage 1, and one complete response out of four Stage 4. We noted nine side effects completely reversible within a month with no late skin reaction. Our results show that hyperthermia can give improved local control without any morbidity in treating chest wall recurrences of breast cancer.

Arterial rupture after microwave-induced hyperthermia and radiotherapy. With reference to two patients treated for recurrence in previously operated and irradiated areas

Two patients who developed frank arterial bleeding after combined microwave-induced hyperthermia and radiotherapy are described. One patient received re-irradiation and hyperthermia for recurrent metastatic neck nodes of a mesopharyngeal carcinoma. Full course radiotherapy had been given 6 years previously and a right-sided radical neck node dissection had been performed 4 months earlier because of recurrent neck node metastases. Six weeks after the combined therapy for a second recurrence, which achieved complete remission, a fatal rupture of the carotid artery occurred. The other patient received re-irradiation and hyperthermia for a chest wall recurrence of a breast carcinoma, treated 5.5 years previously by sector resection and tangential beam radiotherapy, and treated again 2 years earlier with extensive surgery for a local recurrence. A frank arterial bleeding from the treated region was seen after 7 months, but could be arrested with surgery. This important complication in combined hyperthermia and radiotherapy does not seem to have been recognized before. Different explanations are discussed, such as the previous local treatment as well as high temperature and atherosclerosis per se.

Localized current field hyperthermia: effect on normal ocular tissue

Using a 500 kHz radiofrequency electromagnetic heating system, the effects of localized current field hyperthermia in normal rabbit eyes were examined. A specially designed scleral plaque placed on normal rabbit eyes was heated to temperatures of 43 degrees C, 45 degrees C, and 47 degrees C for a period of 45 min. The effects of hyperthermia were monitored by clinical examination, fluorescein angiography, electroretinography and histopathology. A graded effect with increasing temperature was found at the lower temperature, and it was confined to the treatment field. At 47 degrees C the electroretinogram was extinguished due to diffuse photoreceptor damage outside the treatment field, as demonstrated by histopathology and electron microscopy. This study indicates that hyperthermia at 45 degrees C for 45 min is the maximum allowable temperature without causing diffuse retinal damage in the normal rabbit eye.

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.

Interstitial laser hyperthermia: a new approach to local destruction of tumours

The use of local hyperthermia to treat cancer of the internal organs has been limited by the difficulty of controlling delivery of heat and limiting the effects to the tumour, but this can be overcome by using laser light transmitted through thin flexible fibres. Laser energy was delivered to tumours through fibres inserted percutaneously through needles directly into the centre of the tumour area. Ultrasound scanning was used to locate the tumour, position the fibres correctly within the tumour, and monitor the development of thermal necrosis in real time during laser exposure and through the subsequent period of healing. Five patients were treated (one with a tumour of the breast, one with a subcutaneous secondary tumour, one with a recurrent pancreatic tumour, and two with secondary tumours in the liver). Tumour necrosis was found on ultrasonography or computed tomography in all, and there were no immediate or delayed complications. In one patient the size of the isolated secondary tumour in the liver had not increased over 10 months, and he subsequently showed no other evidence of residual cancer. To develop this technique careful studies are essential to ensure that in every case the extent of thermal necrosis produced by absorption of the laser light can be matched to the full extent of the tumour being treated and that there is always sufficient adjacent normal tissue to ensure safe healing. These preliminary results suggest that this simple technique can be applied safely and effectively to common tumours in humans; more extensive trials in a range of cancers of solid organs are warranted.