Important prognostic factors influencing outcome of combined radiation and hyperthermia

Clinical Evidence for Thermometric Parameters to Guide Hyperthermia Treatment

Hyperthermia (HT) is a cancer treatment modality which targets malignant tissues by heating to 40-43 °C. In addition to its direct antitumor effects, HT potently sensitizes the tumor to radiotherapy (RT) and chemotherapy (CT), thereby enabling complete eradication of some tumor entities as shown in randomized clinical trials. Despite the proven efficacy of HT in combination with classic cancer treatments, there are limited international standards for the delivery of HT in the clinical setting. Consequently, there is a large variability in reported data on thermometric parameters, including the temperature obtained from multiple reference points, heating duration, thermal dose, time interval, and sequence between HT and other treatment modalities. Evidence from some clinical trials indicates that thermal dose, which correlates with heating time and temperature achieved, could be used as a predictive marker for treatment efficacy in future studies. Similarly, other thermometric parameters when chosen optimally are associated with increased antitumor efficacy. This review summarizes the existing clinical evidence for the prognostic and predictive role of the most important thermometric parameters to guide the combined treatment of RT and CT with HT. In conclusion, we call for the standardization of thermometric parameters and stress the importance for their validation in future prospective clinical studies.

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.

Synergistic chemotherapy by combined moderate hyperthermia and photochemical internalization

Combination therapies of photochemical internalization (PCI) and moderate hyperthermia (MHT) were investigated in an in vitro system consisting of human and rat glioma spheroids. PCI using the amphiphilic photosensitizer, AlPcS2a and two anti cancer agents BLM or 5-FU were used. Spheroids were irradiated with λ = 670 nm laser light in an incubator at temperatures ranging from 37 to 44°C. For each temperature investigated, spheroids were divided into 4 groups: control, drug-only, photodynamic therapy (PDT), and PCI. PDT and PCI spheroids were exposed to radiant exposures ranging from 0.3 to 2.5 J cm(-2) using an irradiance of 5 mW cm(-2). Toxicity was evaluated from spheroid growth kinetics. The combination of PCI and MHT resulted in significant increases in BLM efficacy at 44°C for both cell line derived spheroids compared to controls at 37°C over the range of radiant exposures examined. 5-FU PCI was ineffective for the human cell line at both 37 and 44°C.

Photothermal enhancement of chemotherapy mediated by gold-silica nanoshell-loaded macrophages: in vitro squamous cell carcinoma study

Moderate hyperthermia (MHT) has been shown to enhance the effects of chemotherapeutic agents in a wide variety of cancers. The purpose of this study was to investigate the combined effects of commonly used chemotherapeutic agents with MHT induced by near-infrared (NIR) activation of gold nanoshell (AuNS)-loaded macrophages (Ma). AuNS-loaded murine Ma combined with human FaDu squamous cells, in hybrid monolayers, were subjected to three cytotoxic drugs (doxorubicin, bleomycin, cisplatin) with or without NIR laser irradiation. For all three drugs, efficacy was increased by NIR activation of AuNS-loaded Ma. The results of this in vitro study provide proof-of-concept for the use of AuNS-loaded Ma for photothermal enhancement of the effects of chemotherapy on squamous cell carcinoma.

Macrophages as nanoparticle delivery vectors for photothermal therapy of brain tumors

Certain types of stem and immune cells, which have an innate ability to target and infiltrate tumors, can be utilized as vectors to deliver several types of anticancer agents. In particular monocytes have the advantage of carrying relatively large payloads of therapeutic nanomaterials, can be patient derived in large numbers and are able to actively infiltrate tumors despite many barriers often present in the microenvironment. Monocytes can selectively cross the compromised blood-brain barrier surrounding brain tumors and are known to actively migrate to hypoxic tumor regions. Of particular interest is the observation that, following near-infrared exposure of tumors containing gold-nanoshell-loaded macrophages, sufficient hyperthermia can be generated to suppress tumor growth. Collectively, these findings demonstrate the potential of monocytes as nanoparticle delivery vectors for several types of site specific light-based cancer therapies.

Combined concurrent photodynamic and gold nanoshell loaded macrophage-mediated photothermal therapies: an in vitro study on squamous cell head and neck carcinoma

BACKGROUND AND OBJECTIVE

Treatment modalities, such as hyperthermia and photodynamic therapy (PDT) have been used in the treatment of a variety of head and neck squamous cell carcinoma (HNSCC), either alone or as an adjuvant therapy. Macrophages loaded with gold nanoshells, which convert near-infrared light to heat, can be used as transport vectors for photothermal hyperthermia of tumors. The purpose of this study was to investigate the effects of combined macrophage mediated photothermal therapy (PTT) and PDT on HNSCC cells.

STUDY DESIGN/MATERIALS AND METHODS

Gold nanoshell loaded rat macrophages either alone or combined with human FaDu squamous cells in hybrid monolayers were subjected to PTT, PDT, or a simultaneous combination of the two light treatments. Therapies were given concurrently employing two laser light sources of λ = 670 nm (PDT) and λ = 810 nm (PTT), respectively.

RESULTS

Significant uptake of gold nanospheres (AuNS) by rat alveolar macrophages was observed thus providing the rationale for their use as delivery vectors. Viability of the AuNS-loaded Ma was reduced to 35 and 12% of control values at an irradiance of 14 or 28 W/cm(2) administered over a 5 minute period respectively. No significant cytotoxicity was observed for empty Ma for similar PTT exposure. AlPcS2a mediated PDT at a fluence level of 0.25 J/cm(2) and PTT at 14 W/cm(2) irradiance had little effect on cell viability for the FaDu/Ma (ratio 2:1) hybrid monolayers. In contrast, combined treatment reduced the cell viability to less than 40% at these same laser power settings.

CONCLUSIONS

The results of this study provide proof of concept for the use of macrophages as a delivery vector of AuNS for photothermal enhancement of the effects of PDT on squamous cell carcinoma. A significant synergy was demonstrated with combined PDT and PTT compared to each modality applied separately.

Hyperthermia for locally advanced breast cancer

Hyperthermia (HT) has a proven benefit for treating superficial malignancies, particularly chest wall recurrences of breast cancer. There has been less research utilising HT in patients with locally advanced breast cancer (LABC), but available data are promising. HT has been combined with chemotherapy and/or radiotherapy in the neoadjuvant, definitive and adjuvant setting, albeit in series with small numbers of patients. There is only one phase III trial that examines hyperthermia in LABC, also with relatively small numbers of patients. The goal of this review is to highlight important research utilising HT in patients with LABC as well as to suggest future directions for its use.

A head and neck hyperthermia applicator: Theoretical antenna array design

PURPOSE

Investigation into the feasibility of a circular array of dipole antennas to deposit RF-energy centrally in the neck as a function of: (1) patient positioning, (2) antenna ring radius, (3) number of antenna rings, (4) number of antennas per ring and (5) distance between antenna rings.

MATERIALS AND METHODS

Power absorption (PA) distributions in realistic, head and neck, anatomy models are calculated at 433 MHz. Relative PA distributions corresponding to different set-ups were analysed using the ratio of the average PA (aPA) in the target and neck region.

RESULTS

Enlarging the antenna ring radius from 12.5 cm to 25 cm resulted in a approximately 21% decrease in aPA. By changing the orientation of the patients with respect to the array an increase by approximately 11% was obtained. Increase of the amount of antenna rings led to a better focussing of the power (1 --> 2/3: approximately 17%). Increase of the distance between the antenna rings resulted in a smaller (more target region conformal) focus but also a decreased power penetration.

CONCLUSIONS

A single optimum array setup suitable for all patients is difficult to define. Based on the results and practical limitations a setup consisting of two rings of six antennas with a radius of 20 cm and 6 cm array spacing is considered a good choice providing the ability to heat the majority of patients.

Electromagnetic Head-And-Neck Hyperthermia Applicator: Experimental Phantom Verification and FDTD Model

PURPOSE

To experimentally verify the feasibility of focused heating in the neck region by an array of two rings of six electromagnetic antennas. We also measured the dynamic specific absorption rate (SAR) steering possibilities of this setup and compared these SAR patterns to simulations.

METHODS AND MATERIALS

Using a specially constructed laboratory prototype head-and-neck applicator, including a neck-mimicking cylindrical muscle phantom, we performed SAR measurements by electric field, Schottky-diode sheet measurements and, using the power-pulse technique, by fiberoptic thermometry and infrared thermography. Using phase steering, we also steered the SAR distribution in radial and axial directions. All measured distributions were compared with the predictions by a finite-difference time-domain-based electromagnetic simulator.

RESULTS

A central 50% iso-SAR focus of 35 +/- 3 mm in diameter and about 100 +/- 15 mm in length was obtained for all investigated settings. Furthermore, this SAR focus could be steered toward the desired location in the radial and axial directions with an accuracy of approximately 5 mm. The SAR distributions as measured by all three experimental methods were well predicted by the simulations.

CONCLUSION

The results of our study have shown that focused heating in the neck is feasible and that this focus can be effectively steered in the radial and axial directions. For quality assurance measurements, we believe that the Schottky-diode sheet provides the best compromise among effort, speed, and accuracy, although a more specific and improved design is warranted.

Temperature data analysis for 22 patients with advanced cervical carcinoma treated in Rotterdam using radiotherapy, hyperthermia and chemotherapy: a reference point is needed

INTRODUCTION

The growing interest and participation in multi-institutional trials involving deep hyperthermia treatment is an important step towards the further consolidation of hyperthermia as an oncological treatment modality. However, the differences in the clinical procedures of hyperthermia application also raises questions as how to compare the reported temperatures data obtained by the different institutes. In this study our recent developed approach, RHyThM (Rotterdam Hyperthermia Thermal Modulator), has been used for thermal data analysis to investigate the temperature dynamics behaviour of a series of deep hyperthermia treatments.

PATIENTS AND METHODS

All 22 patients (104 hyperthermia treatments) with locally advanced cervical carcinoma who participated in a feasibility study for treatment with a three-modality therapy were selected. The patients received mega-voltage external beam radiotherapy to the pelvis in daily fractions of 2 Gy five times a week to a total dose of 46 Gy and additional brachytherapy, at least four courses of weekly cisplatin (40 mg m-2) and five sessions of weekly loco regional deep hyperthermia treatments with the BSD2000-3D with the Sigma 60 or the Sigma-eye applicators at frequencies 70-120 MHz. Using RHyThM tissue type was defined along the insertion length, based on the CT scan information in radiotherapy position, for each single treatment. A step change in the slope of the profile of the first temperature map was identified to verify the insertion length of the thermometry catheter and precise location of the transition between in- and outside the body. Data analysis was performed based on the temperature readout provided by RHyThM.

RESULTS

The temperature and RF-power data of 97 treatments could be analysed. The intra-vaginal temperature indices were slightly lower than those for bladder and rectum. The average T50 (median temperature) in all lumens, i.e. bladder, vagina and rectum, was 40.4 +/- 0.6 degrees Celsius. The average vagina all lumen T50 was 40.0 +/- 0.8 degrees Celsius. The average bladder and rectum all lumen T50 was 40.6 +/- 0.7 degrees Celsius and 40.5 +/- 0.6, respectively. When the analysis was restricted to the deepest 5 cm of the vagina lumen, the average T50 was 39.8 +/- 0.9 degrees Celsius. Good correlation exists between the various temperature indices like T20, T50 and T90, for all lumen measurements in bladder, vagina and rectum. No correlation was found between temperature indices and treatment number. For the complete patient population, no relationship was found between T50 and net integrated RF-power applied. In an explorative analysis on individual patients a positive correlation coefficient or trend was found in 14 patients between normalized net integrated RF-power and vagina T50.

CONCLUSION

Average all lumen T50 for bladder, vagina and rectum differ less than 1 degrees Celsius, indicating that a large volume was heated relatively homogeneously. The vagina T50 value depends on how many measurement points are included for the analysis. In this group of patients the vagina T50 of the first treatment is not a good measure to discriminate between patients with 'heatable' and 'non-heatable' tumours. In order to compare temperature data reported by different institutes dealing with the same group of patients, one needs a strict and clear agreement on which temperature measurements or reference point(s) that should be included in the analysis.

Radiotherapy with 8 MHz radiofrequency-capacitive regional hyperthermia for pain relief of unresectable and recurrent colorectal cancer

PURPOSE

The purpose of this study was to assess the pain relief in patients with unresectable and recurrent colorectal cancer treated with radiation plus 8 MHz radiofrequency-capacitive regional hyperthermia and to identify predictors of the good outcome.

METHODS

Between February 1986-May 2003, 41 patients with primarily unresectable and recurrent colorectal cancer that caused pain were treated with thermoradiotherapy at the hospital and retrospectively analysed. Radiotherapy was administered with a mean total radiation dose of 56 Gy. Hyperthermia was usually applied within 30 min after radiotherapy once or twice a week. For cooling of the skin surface, the overlay boluses were applied in addition to regular boluses. The external cooling unit has been used to reinforce the cooling ability of the overlay bolus and achieve strong surface cooling to reduce the preferential heating of the subcutaneous fat tissue and treat with more RF-output in 17 patients since January 1997.

RESULTS

Pain relief was obtained in 83% of the patients. Multi-variate analysis by logistic regression to evaluate the effects of certain factors on pain relief (complete response + good response) was strongly correlated with the presence of radiating pain to leg(s) (p < 0.05). The median follow-up was 18 months. The median duration of pain relief was 7.0 months. For the 27 patients in whom the tumour temperature was estimated, the median duration of pain relief was 14.6 months for the patients with a mean average tumour temperature of > 42.5 degrees C and 5.7 months for those of < 42.5 degrees C (p < 0.05). In the 18 patients with radiating pain to leg(s), use of strong superficial cooling and the higher numbers of hyperthermia treatments were better prognostic factors for the duration of pain relief (p < 0.01 and p < 0.05, respectively).

CONCLUSIONS

Radiotherapy with 8 MHz radiofrequency-capacitive regional hyperthermia provided an efficient, effective means on pain relief of treating unresectable and recurrent colorectal cancer. The duration of pain relief can be prolonged, if an adequate heating is achieved, especially in the patients with radiating pain to the leg(s).

Theoretical investigation into the feasibility to deposit RF energy centrally in the head-and-neck region

PURPOSE

To investigate the ability to deposit radiofrequency energy centrally in the neck as a function of antenna positions, number of antennas, and operating frequency.

METHODS AND MATERIALS

Power absorption (PA) distributions in a realistic model of the head-and-neck anatomy are calculated in which the head model is irradiated by an array of dipole antennas. The relative PA distributions corresponding to different setups are visualized and analyzed using the ratio of the average PA (aPA) in the target and neck region.

RESULTS

Both the PA distributions and aPA ratios indicate an optimal focusing ability of the setups (i.e., the ability to direct energy efficiently into the target region), between 400 and 600 MHz. In this frequency band, the focusing ability depends only moderately on the size of the neck. Finally, it is found that the focusing ability at 433 MHz is increased significantly by increasing the number of antenna elements.

CONCLUSIONS

The optimal frequency is found to be highly dependent on the size of the target volume; thus, a single optimum is hard to define. However, future clinical research will focus on 433 MHz based on the optimal range of frequencies, as found in this study.

A moderate elevation of blood glucose level increases the effectiveness of thermoradiotherapy in a rat tumor model II. Improved tumor control at clinically achievable temperatures

PURPOSE

To assess the therapeutic gain (at the TCD(50) level) that can be obtained by boosting thermoradiotherapy with intravenous glucose infusion at different temperatures. This completes our series of studies to determine the optimal conditions and the effectiveness of glucose administration at clinically achievable glucose levels and treatment temperatures.

METHODS AND MATERIALS

Subcutaneous rat rhabdomyosarcoma BA1112 was irradiated with graded single doses of 300-kV X-rays (dose range 0-60 Gy). Fifteen minutes after irradiation, a 100-min intravenous infusion was started, consisting of either glucose (20% solution, 2.4-3 g/kg/h) or saline as a control. Then heat was applied to the tumors at 42 degrees C or 43 degrees C (water bath) during a subsequent 100-min period of infusion. Tumor control was scored as the absence of palpable growth at 100 days after treatment.

RESULTS

Glucose infusion enhanced tumor control independent of temperature in the range 42-43 degrees C. At 42 degrees C, the TCD(50) for X-irradiation decreased by 5.9 Gy (SEM 1.8 Gy), from 41.6 (1.6) to 35.7 (1.5) Gy, and at 43 degrees C from 33.3 (1.6) to 27.3 (1.5) Gy, representing a glucose enhancement ratio of approximately 1.2. At doses corresponding to the TCD(50) at either 42 or 43 degrees C, the addition of glucose increased tumor control from 50% to 70%. An enhancement ratio of 2.1 was found for the combination of irradiation, glucose infusion, and heating at 43 degrees C, with respect to irradiation alone (TCD(50) 56.3 Gy, reanalyzed earlier data). The contribution of combined heat and glucose to tumor control represented an additive effect, probably on the hypoxic cell population.

CONCLUSION

Moderate glucose administration (blood concentration 300 mg/100 mL) sizably improves experimental tumor control after combined X-irradiation and hyperthermia under clinically feasible conditions. Clinical treatment should benefit from this additional modality, in particular if unsatisfactory local control rates are due to insufficient heating. The therapeutic gain has to be evaluated further in clinical studies.

Augmentation in chemosensitivity of intratumor quiescent cells by combined treatment with nicotinamide and mild hyperthermia

C3H/He and Balb/c mice bearing SCC VII and EMT6/KU tumors, respectively, received continuous administration of 5-bromo-2'-deoxyuridine (BrdU) for 5 days using implanted mini-osmotic pumps to label all proliferating (P) cells. Nicotinamide was administered intraperitoneally before cisplatin injection and/or tumors were locally heated at 40 degrees C for 60 min immediately after cisplatin injection. The tumors were then excised, minced and trypsinized. The tumor cell suspensions were incubated with cytochalasin-B (a cytokinesis-blocker), and the micronucleus (MN) frequency in cells without BrdU labeling (quiescent (Q) cells) was determined using immunofluorescence staining for BrdU. The MN frequency in total (P+Q) tumor cells was determined from tumors that had not been pretreated with BrdU labeling. The sensitivity to cisplatin was evaluated in terms of the frequency of induced micronuclei in binuclear tumor cells (MN frequency). In both tumor systems, the MN frequency in Q cells was lower than that in the total cell population. Nicotinamide treatment elevated the MN frequency in total SCC VII cells. Mild heating raised the MN frequency more markedly in Q cells than in total cells. The combination of nicotinamide and mild heat treatment increased the MN frequency more markedly than either treatment alone. In total SCC VII cells, nicotinamide increased 195mPt-cisplatin uptake. Mild heating elevated 195mPt-cisplatin uptake in total EMT6/KU cells. Cisplatin-sensitivity of Q cells was lower than that of total cells in both tumor systems. Nicotinamide sensitized tumor cells including a large acutely hypoxic fraction, such as those of SCC VII tumors, through inhibition of the fluctuations in tumor blood flow. Tumor cells including a large chronically hypoxic fraction such as Q cells were thought to be sensitized by mild heating through an increase in tumor blood flow.

Reduction of hypoxic cells in solid tumours induced by mild hyperthermia: special reference to differences in changes in the hypoxic fraction between total and quiescent cell populations

C3H/He mice bearing SCC VII tumours received 5-bromo-2'-deoxyuridine (BrdU) continuously for 5 days via implanted mini-osmotic pumps in order to label all proliferating (P) cells. The tumours were then heated at 40 degrees C for 60 min. At various time points after heating, tumour-bearing mice were irradiated while alive or after being killed. Immediately after irradiation, the tumours were excised, minced and trypsinized. The tumour cell suspensions obtained were incubated with cytochalasin-B (a cytokinesis blocker), and the micronucleus (MN) frequency in cells without BrdU labelling, which could be regarded as quiescent (Q) cells, was determined using immunofluorescence staining for BrdU. The MN frequency in the total (P+Q) tumour cell population was determined from the irradiated tumours that were not pretreated with BrdU. The MN frequency of BrdU unlabelled cells was then used to calculate the surviving fraction of the unlabelled cells from the regression line for the relationship between the MN frequency and the surviving fraction of total (P+Q) tumour cells. In general, Q cells contained a greater hypoxic fraction (HF) than the total tumour cell population. Mild heating decreased the HF of Q cells more markedly than in the total cell population, and the minimum values of HFs of both total and Q cell populations were obtained 6 h after heating. Two days after heating, the HF of total tumour cells returned to almost that of unheated tumours. In contrast, the HF of Q cells did not return to the HF level of unheated tumours until 1 week after heating. It was thought that irradiation within 12 h after mild heating might be a potentially promising therapeutic modality for controlling radioresistant Q tumour cells.

Radiation plus local hyperthermia versus radiation plus the combination of local and whole-body hyperthermia in canine sarcomas

PURPOSE

The purpose of this study was to assess the effect of increasing intratumoral temperatures by the combination of local hyperthermia (LH) and whole body hyperthermia (WBH) on the radiation response of canine sarcomas.

METHODS AND MATERIALS

Dogs with spontaneous soft tissue sarcomas and no evidence of metastasis were randomized to be treated with radiation combined with either LH alone or LH + WBH. Dogs were accessioned for treatment at two institutions. The radiation dose was 56.25 Gy, given in 25 2.25 Gy daily fractions. Two hyperthermia treatments were given; one during the first and one during the last week of treatment. Dogs were evaluated after treatment for local recurrence, metastasis, and complications.

RESULTS

Sixty-four dogs were treated between 1989 and 1993. The use of LH+WBH resulted in statistically significant increases in the low and middle regions of the temperature distributions. The largest increase was in the low temperatures with median CEM 43 T90 values of 4 vs. 49 min for LH vs. LH + WBH, respectively (p<0.001). There was no difference in duration of local tumor control between hyperthermia groups (p = 0.59). The time to metastasis was shorter for dogs receiving LH + WBH (p = 0.02); the hazard ratio for metastatic disease for dogs in the LH + WBH group was 2.4 (95% confidence interval, 1.2-5.4) with respect to dogs in the LH group. Complications were greater in larger tumors and in tumors treated with LH + WBH, CONCLUSION: The combination of LH + WBH with radiation therapy, as described herein, was not associated with an increase in local tumor control in comparison to use of LH with radiation therapy. The combination of LH + WBH also appeared to alter the biology of the metastatic process and was associated with more complications than LH. We identified no rationale for further study of LH + WBH in combination with radiation for treatment of solid tumors.

Estimation of cell survival in tumours heated to nonuniform temperature distributions

A stochastic model describing the probability of cell survival as a function of thermal exposure was developed and fit to data arising from studies of CHO cell survival under hyperthermic conditions. This model characterizes the separate risks of temperature-induced cell death and induction of thermotolerance during heating. Tumour cells are assumed to be affected independently of each other by hyperthermia. Tumour geometry, perfusion and power deposition affect hyperthermia-induced temperature distributions in tumours, producing nonuniform temperatures. Two tumours may respond to hyperthermia slightly differently because of differences in tumour geometry, perfusion, power deposition, or by chance alone and the approach presented here incorporates chance and these other factors explicitly.

THE RESULTS

(1) the time-temperature history is important for estimating tumour cell survival; (2) tumour temperature heterogeneity leaves more surviving cells at a given T90 temperature than would be expected if the entire tumour were uniformly heated to that same temperature; and (3) changes in the shape of the temperature distribution because of tumour geometry and perfusion distribution greatly influence cell survival between tumours, even when the standard temperature descriptors, such as T90, are fixed. The simulations also showed a modest effect on cell kill attributable to varying the lengths of the warm-up and the cool-down periods. These simulations indicate that these types of sensitivity studies can be used to investigate relationships between various modifiers of temperature distributions achieved when treating tumours with hyperthermia and to assess their potential therapeutic impact in clinical trials.

The effect of heat on Na+/H+ antiport function and survival in mammalian cells

PURPOSE

Because intracellular pH (pHi) is a determinate of thermosensitivity, it is important to understand the relationship between heat cytotoxicity and the mechanisms responsible for pHi regulation, such as the Na+/H+ antiport. The objective of this study is to elucidate the relationship between heat damage and Na+/H+ antiport activity.

METHODS AND MATERIALS

Various cell lines, EMT6, RIF-1, and its thermoresistant variant TR-4, and CCL39, and its variant that lacks the Na+/H+ antiport (PS120), were all heated using a water bath. Parallel assessments of antiport function and pHi were made using the fluorescent dye 2,7-biscarboxyethyl-5(6)-carboxyfluorescein (BCECF).

RESULTS

Exposure of EMT6 cells to 43-46 degrees C for 30-60 min caused progressive decline in antiport activity, in parallel with cytotoxicity. When the same degree of cytotoxicity was induced by ionizing radiation, no alteration in Na+/H+ antiport function was observed. Despite a 10-fold lower survival in RIF-1 compared to TR-4 cells after heating, there was no difference in the thermosensitivity of their antiports. Antiport activity in the TR-4 cells, however, was higher than that of RIF-1 cells both before and during heating. Intracellular pH for TR-4 cells decreased minimally during heating, in contrast to a decline of 1 pH unit in RIF-1 cells despite similar relative levels of antiport activity, suggesting that in this pair of cell lines, antiport activity does not play a major pHi regulatory role. PS120 and CCL39 cells and similar survival levels when heated at pHe 7.2 in the presence of NaHCO3, which allows function of the other major regulator of pHi, the Na+ -dependent HCO3-/Cl- exchanger. This occurred despite a drop in pHi in the PS120 cells during heating. A reduced survival was observed, however, in PS120 cells after 43 degrees C for 30-60 min at either pHe 6.5 or pHe 7.2 in the absence of NaHCO3. Intracellular pH was consistently greater for PS120 than CCL39 cells.

CONCLUSION

We demonstrated that damage to the Na+/H+ antiport likely reflects early heat-induced change in membrane function, but is not a primary target for heat cytotoxicity. Although there is an association between survival, antiport function, and pHi level under most treatment conditions, the precise role of the Na+/H+ antiport in mediating thermal cytotoxicity remains uncertain.

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.

Hyperthermia as an adjuvant to radiation therapy of recurrent or metastatic malignant melanoma. A multicentre randomized trial by the European Society for Hyperthermic Oncology

The ESHO protocol 3-85 is a multicentre randomized trial investigating the value of hyperthermia as an adjuvant to radiotherapy in treatment of malignant melanoma. A total of 134 metastatic of recurrent malignant melanoma lesions in 70 patients were randomized to receive radiotherapy alone (3 fractions in 8 days) or each fraction followed by hyperthermia (aimed for 43 degrees C for 60 min). Radiation was given with high voltage photons or electrons. Tumours were stratified according to institution and size (above or below 4 cm) and randomly assigned to a total radiation dose of either 24 or 27 Gy to be given with or without hyperthermia. The endpoint was persistent complete response in the treated area. A number of 128 tumours in 68 patients were evaluable, with an observation time between 3 and 72 months. Sixty-five tumours were randomized to radiation alone and 63 to radiation + heat. Sixty received 24 Gy and 68 tumours received 27 Gy, respectively. Size was < or = 4 cm in 81 and > 4 cm in 47 tumours. Overall the 2-year actuarial local tumour control was 37%. Univariate analysis showed prognostic influence of hyperthermia (rad alone 28% versus rad + heat 46%, p = 0.008) and radiation dose (24 Gy 25% versus 27 Gy 56%, p = 0.02), but not of tumour size (small 42% versus large 29%, p = 0.21). A Cox multivariate regression analysis showed the most important prognostic parameters to be: hyperthermia (odds ratio: 1.73 (1.07-2.78), p = 0.02), tumour size (odds ratio: 0.91 (0.85-0.99), p = 0.05) and radiation dose (odds ratio: 1.17 (1.01-1.36), p = 0.05). Analysis of the heating quality showed a significant relationship between the extent of heating and local tumour response. Addition of heat did not significantly increase the acute or late radiation reactions. The overall 5-year survival rate of the patients was 19%, but 38% in patients if all known disease was controlled, compared to 8% in the patients with persistent active disease.

Thermoradiotherapy of superficial and subsurface tumours: analysis of thermal parameters and tumour response

Between 1988 and 1993, 57 superficial and subsurface tumours of various tumour type were treated with a 430-MHz microwave heating device. Mean (range) tumour depth of the 57 tumours was 3.0 (0.5-6.5) cm. Fifty-four tumours were treated with thermoradiotherapy. Total radiation dose ranged from 20 to 70 Gy with a mean of 53 Gy. For the remaining three tumours, thermochemotherapy was performed. Hyperthermia was given once a week, and a total of 207 heat sessions was administered. Our goal of hyperthermia treatment was to elevate all monitored tumour points > 41 degrees C for > 30 min. The mean (range) number of intratumoral thermometry points was 3.7 (2-6). The goal of hyperthermia treatment was achieved in 49% of the sessions. At the time of maximum tumour regression, complete response was noted in 53% of the tumours treated with thermoradiotherapy. Univariate analysis demonstrated that parameters including tumour type (breast cancer versus others), tumour depth, minimum tumour temperature, average tumour temperature, minimum equivalent time at 43 degrees C, and number of heat sessions achieving the treatment goal significantly affected the tumour response of the combined treatment, while total radiation dose and number of heat sessions were not significant factors for tumour response. Multivariate logistic analysis revealed that only tumour depth (< 3 versus > or = 3 cm) was a significant prognostic factor for tumour response (p = 0.029). Tumour type (breast cancer versus others) and a number of heat sessions achieving the treatment goal (0-1 versus 2-5) were found to be of borderline significance in the multivariate analysis (p = 0.075 and 0.097 respectively). The number of heat sessions achieving a minimum tumour temperature of > 41 degrees C for > 30 min seems a practical thermal parameter that influences tumour response. The present study indicates the importance of quality and quantity of heat session on the treatment outcome of thermoradiotherapy.

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.

Eugene Robertson Special Lecture. Hyperthermia from the clinic to the laboratory: a hypothesis

Recently reported thermal isoeffective dose-response relationships in human tumours confirm the existence of an effect of hyperthermia in combination with radiotherapy. The prognostically important thermal doses are based upon the lowest temperatures achieved within tumours, and these thermal doses are well below those used in most laboratory studies that have provided the rational for hyperthermia treatment. Direct thermal cytotoxicity and thermal radiosensitization are insignificant at these low thermal doses. Other explanations for the mechanism of hyperthermia effect appear warranted. We hypothesize that hyperthermia at low thermal doses causes reoxygenation and hence direct radiosensitization in vivo.

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.

A new applicator utilizing distributed electrodes for hyperthermia: a theoretical approach

We propose a new type of applicator for hyperthermia namely a Distributed Electrodes Applicator. Many electrodes are fixed on boli below which the patient is placed. A set of RF with optimized amplitudes and phases is supplied to the electrodes so as to minimize the ratio of SAR (specific absorption rate) in the fat layers to that in the central region of the patient. SAR patterns in a heated material were calculated using two-dimensional finite element method, and the results showed that the proposed applicator can heat the deep portions of the patient without excessive heating of the fat layers.

Multiple field hyperthermia combined with radiotherapy in advanced carcinoma of the breast

Extensive recurrences on the chest wall of advanced carcinoma of the breast in 20 patients were treated with multiple field patchwork hyperthermia combined with radiation therapy between 1987-1991. The objective of the study was to evaluate the feasibility, tumour response and complications of treating extensive lesions with multiple, overlapping fields of hyperthermia. All lesions were diffuse encompassing up to 2900 cm2 in area with or without multiple nodules < or = 3 cm deep. All lesions had failed previous therapy with all but three failing previous radiotherapy. Hyperthermia consisted of 282 hyperthermia applicator fields and 357 hyperthermia treatments with external 915 MHz microwaves using commercially available applicators. Hyperthermia applicator fields were defined by the surface 50% SAR distribution of a particular applicator, and hyperthermia fields were abutted to cover the entire tumour bearing area. Radiation therapy consisted of 81 fields to a mean dose of 40 +/- 1 Gy (SE), 88% of fields received between 30 and 50 Gy. The equivalent dose was 42 +/- 1 Gy, based on the linear-quadratic model and alpha/beta = 25 (Fowler 1989). Overlapping hyperthermia fields were separated by an interval of at least three days. Up to four heat sessions per week were required to cover the entire tumour in a rotating fashion. The hyperthermia treatment time was 60 min. Hyperthermia treatments were continued for the duration of radiation therapy. Each hyperthermia applicator field was heated at least once. Patients were exposed to a mean of 14 +/- 3 hyperthermia applicator fields (range of 3-46 fields) and a mean of 18 +/- 3 hyperthermia treatments (range of 6-61) delivered over a mean of 7.5 +/- 0.9 weeks (range of 3-17 weeks). Each field was heated an average of 1.3 times. The tumour complete response rate was 95% with a recurrence rate of 5%. Nevertheless, the mean survival of patients with a complete response was only 10.8 +/- 1.7 months (range of 2-28 months) because of the systemic tumour burden existing outside of the treated fields in these patients. Neither complete response, local control nor survival after thermoradiotherapy correlated with the disease free interval between initial mastectomy and recurrence. There was no evidence of increased thermal damage to skin nor evidence of tumour recurrence at junctions of hyperthermia field overlap. It is concluded that recurrent advanced carcinoma of the breast presenting as extensive, diffuse lesions on the chest wall can be treated as effectively with multiple field patchwork thermoradiotherapy as can nodular lesions treated with single hyperthermia fields.

Effect of vascular occlusion on tumour temperatures during superficial hyperthermia

Tumour temperature heterogeneity during hyperthermia has been attributed to irregular tumour vascular perfusion. We have compared temperature distributions in human tumours subjected to superficial hyperthermia under conditions of normal and occluded blood flow. Three patients with recurrent malignant melanoma on the leg were treated with radiation followed by hyperthermia 60-90 min later on days 1, 8 and 22. Heating (15-30 min) with normal blood flow was followed by 15 min of heating with tourniquet occlusion, although the tourniquet had to be intermittently released when the patients complained of discomfort. Hyperthermia was delivered using either a 1.4 MHz ultrasound or 915 MHz microwave applicator. Temperatures were monitored using superficial and interstitial thermometers in tumour and normal tissues. When the tourniquet was applied, the amount of power required to maintain peak temperatures was decreased by a factor of 3-10. With normal blood flow, there was a significant degree of temperature heterogeneity within the treatment volume, both within normal and tumour tissues, which improved with tourniquet application. The T90 and T50 indices increased both in normal tissues and tumour following the tourniquet occlusion, with the temperature increments being greater for normal tissues. Temperatures at depth were increased despite the reduction in applied power and the temperature profiles were smoother when the tourniquet was applied. No cutaneous, vascular or neuromuscular side effects were observed amongst these three subjects either acutely or at 1 month follow-up. These studies demonstrate directly that the temperature heterogeneity which exists in human tumours subjected to external heating can be reduced by occluding the blood supply.

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).

Report of long-term follow-up in a randomized trial comparing radiation therapy and radiation therapy plus hyperthermia to metastatic lymph nodes in stage IV head and neck patients

PURPOSE

The treatment of inoperable metastatic lymph nodes in patients with head and neck cancer represents a therapeutic challenge. Clinical results using conventional radiation therapy are disappointing; on the other hand, the evaluation of recent innovative radiotherapeutic methods is still pending. The end points of this analysis were focused on long-term local control, on its potential influence on survival, and on late toxicity of a previously reported randomized Phase III study comparing conventionally fractionated radical irradiation alone or combined with local hyperthermia in fixed and inoperable metastatic neck lymph nodes.

METHODS AND MATERIALS

The medical records of 41 patients (44 nodes) with advanced locoregional Stage IV squamous cell cancer of the head and neck and randomized to treatment in the period 1985-1986 with irradiation alone (22/23 evaluable nodes) or combined with external hyperthermia (18/21 evaluable nodes), were re-evaluated.

RESULTS

The statistically significant difference observed in "early" response (p = 0.0164) in favor of the combined treatment results in improved 5-year actuarial nodal control (p = 0.015). Clinical improvement noted in tumor control positively affects survival, leading to a statistically significant difference in survival at 5 years (p = 0.02). With respect to side effects, no clearly enhanced acute or late toxicity has been found; as severe late effects, two patients with bone necroses possibly related to the combined treatment have been observed. Thermal analysis failed to show a significant correlation between heating parameters and the end points of the study.

CONCLUSION

This report with 5-year follow-up confirms the efficacy and the absence of severe toxicity of the combination of radical radiation and hyperthermia in the treatment of metastatic lymph nodes in Stage IV squamous cell carcinoma of the head and neck.

Temperature differentials between treatment and pretreatment temperatures correlate with local control following radiotherapy and hyperthermia

PURPOSE

To evaluate the influence of pretreatment tumor temperatures and the temperature differential between treatment and pretreatment temperatures on local tumor control in patients who underwent combined radiation therapy and hyperthermia.

METHODS AND MATERIALS

Mapped intratumoral temperatures were measured immediately prior to and during hyperthermia in 138 hyperthermia fields among 59 patients with nodular (60 fields) or diffuse (78 fields) superficially-located tumors. In the nodular subgroup there were 40 fields with adenocarcinomas (31 breast, two prostate, seven other primary sites), six melanomas, nine squamous cell carcinomas, and five other histologies. The fields with diffuse tumor involvement consisted of 77 adenocarcinomas (67 breast, 10 other) and one melanoma. The maximum, minimum, and average temperatures were determined for both the pretreatment (pTmax, pTmin, pTave) and treatment (Tmax, Tmin, Tave) distributions and the differences, Dm = Tmin-pTmax, and Da = Tmin-pTave, computed. These quantities were averaged over treatments to produce the corresponding mean quantities for each hyperthermia field. Univariate and multivariate analyses were performed to determine treatment and pretreatment parameters which best correlated with the duration of local control.

RESULTS

Pretreatment tumor temperatures were significantly lower than the oral temperatures with mean pTmax, mean pTmin, and mean pTave of 36.2 degrees C, 34.2 degrees C, and 35.4 degrees C, respectively. For the adenocarcinomas with diffuse involvement within the hyperthermia field, the covariates best correlating with local control duration on univariate analysis were concurrent radiation dose (p = 0.0026), Dm (p = 0.009), pTmax (p = 0.012) and Da (p = 0.036). Lower pTmax and larger Dm and Da were predictive for longer local control. In multivariate analyses, all thermal parameters lost power, however, the best model included Dm which was significant at the p = 0.040 level. For the nodular subgroup, nonthermal parameters and dichotomized thermal parameters were of prognostic significance for local control.

CONCLUSION

For fields diffusely involved with adenocarcinoma significant correlations with duration of local control have been demonstrated both for a) low pretreatment temperatures and b) large differentials between treatment and pretreatment intratumoral temperatures. These correlations were also found in a dichotomized description for fields with nodular tumors. The results support the concept that pretreatment hypothermic conditions can lead to an increase in thermal sensitization and may help explain the excellent clinical results noted in the treatment of superficial tumors with radiation and hyperthermia. Further exploitation of this approach by planned cooling of superficially-located recurrent tumors prior to hyperthermia treatment warrants investigation.

'Patchwork' fields in thermoradiotherapy for extensive chest wall recurrences of breast carcinoma

Chest wall lesions of advanced breast carcinoma in 23 patients were treated with thermoradiotherapy with clinical intent between January 1987 and March 1992. Treatment consisted of external 915 MHz microwave hyperthermia with commercially available applicators and radiation therapy to doses between 32-58 Gy. Twenty-three large, diffuse lesions were treated with multiple field patchwork hyperthermia. All lesions were diffuse with or without multiple nodules < or = 3 cm depth. All lesions had failed previous therapy. The mean number of hyperthermia fields per patient was 3.2 +/- 0.4 (range of 2-7). The complete response rate was 91% in this group of extensive, diffuse lesions treated by the patchwork technique. Mean total radiation dose administered concurrently with multiple field patchwork hyperthermia was 42 +/- 1 Gy. The recurrence rate was 5%. The mean survival in patients who had a complete response was 9.0 +/- 1.3 months. The reduced survival among patchwork treated patients was due to the extensive tumor burden existing outside of the treated fields in these patients. The skin reactions were minor, causing minimal discomfort. There was no evidence of increased thermal damage to skin, or of tumor recurrence at junctions of hyperthermia field overlap. It is concluded that extensive, diffuse lesions of chest wall recurrence of advanced carcinoma of the breast can be treated effectively with multiple field patchwork thermotherapy.

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.

Randomized trial of one versus two adjuvant hyperthermia treatments per week in patients with superficial tumours

One test for thermotolerance development in a clinical situation is to evaluate the effects of altering the hyperthermia fractionation interval on tumour response to thermoradiotherapy. Between 1983 and 1990 44 evaluable advanced superficial tumours of miscellaneous origin in 41 patients were randomized to receive either once-weekly or twice-weekly external microwave hyperthermia treatments combined with radiation therapy. The mean age of patients was 62 years, and 85% had failed previous therapy. All lesions were less than 8 x 8 x 4 cm (L x W x D) and were heated by external 915 MHz microwaves. The mean radiation dose was 44 +/- 3 Gy (mean +/- SE) in the once-weekly group and 46 +/- 3 Gy in the twice-weekly group (p = 0.64). The mean volume of the lesions heated once weekly was 17 +/- 6 versus 23 +/- 5 cm3 for those heated twice weekly (p = 0.45). Hyperthermia was administered once weekly for 4.6 +/- 0.2 sessions (range 3-7) or twice weekly for 8.1 +/- 0.3 sessions (range 4-10). Thermometry was performed using 3.4 +/- 0.2 catheters and 5.1 +/- 0.6 thermal sensors per tumour in the once-weekly group, and 2.7 +/- 0.2 catheters and 5.8 +/- 0.3 thermal sensors per tumour in the twice-weekly group. Of the 44 evaluable randomized lesions a complete response (CR) at 2 months post-treatment was observed in 59% (13/22) heated once weekly and 55% (12/22) in those heated twice weekly. The prognostic factors predictive of tumour complete response were found by logistic regression analysis to be radiation dose and tumour volume, while the prognostic factors predictive of duration of response (Cox proportional hazards analysis) were median minimum tumour temperature (Tmin), minimum tumour temperature during the first heat treatment (Tmin1) and tumour volume. The duration of local control in lesions with Tmin < or = 39.5 degrees C was 11.7 +/- 1.9 months while for lesions with Tmin > 39.5 degrees C it was 23.0 +/- 4.2 months (p = 0.01). The ED50 was calculated by logistic regression to be 40 Gy (95% CI = 22-54 Gy) for once- and twice-weekly heated lesions. There was not a significant difference in tumour response or duration of response between populations randomized to receive once- versus twice-weekly hyperthermia treatments. There was also no difference in skin reaction rates between once- and twice-weekly hyperthermia treatments, nor could a correlation be found between any thermal parameter and skin reactions.(ABSTRACT TRUNCATED AT 400 WORDS)

Deep regional hyperthermia: comparison between the annular phased array and the sigma-60 applicator in the same patients

PURPOSE

Several institutions have accumulated clinical experience with the annular array as well as with the Sigma applicator. There exist only limited data in comparison of both heating devices possibly favoring the annular array over the Sigma applicator with regard to tumor temperatures and acute toxicity. The objective of this study was to record temperature distributions at identical sites in tumor and normal tissue in the same patients treated with each device.

METHODS AND MATERIALS

Eighteen patients with advanced pelvic tumors were treated on successive occasions with regional hyperthermia using the annular phased array applicator usually driven at 60-80 MHz or the Sigma applicator usually driven at 70-90 MHz. In all patients detailed thermal mapping and temperature analysis for tumor and normal tissues could be performed.

RESULTS

Regardless the device used the acute toxicity was treatment limiting in nearly 50% of the treatments. Systemic stress was treatment limiting in 30% of the treatments with both devices although systemic parameters (core temperature, heart rate, changes in blood pressure) were higher with the annular array. The overall mean minimum, average and maximum tumor temperature observed were 39.5 +/- 1.0 degrees C, 40.9 +/- 1.4 degrees C, 42.7 +/- 2.3 degrees C for the annular array and 39.3 +/- 0.9 degrees C, 40.9 +/- 1.4 degrees C, and 42.5 +/- 1.7 degrees C for the Sigma applicator. The time-averaged temperatures achieved in 20% (T20), 50% (T50) and 90% (T90) of all measured sites were 41.7 +/- 2.1 degrees C, 40.8 +/- 1.4 degrees C, 39.9 +/- 1.2 degrees C for the annular array and 41.7 +/- 1.4 degrees C, 41.0 +/- 1.3 degrees C, and 40.1 +/- 1.0 degrees C, for the S-60. The difference was not statistically significant. With regard to normal tissue temperatures a trend to higher maximum temperatures in the deep muscle and fat tissue was evident for the Sigma applicator. The overall minimum and average normal tissue temperatures in the deep muscle and fat tissue and the rectum and the time-averaged temperatures achieved in 20% (T20), 50% (T50) and 90% (T90) of the measured sites differ not statistically significant.

CONCLUSION

These results indicate that there continue to be unresolved limitations in achieving temperature elevation in deep seated tumors of the pelvis with radiative coherent EM wave techniques using amplitude and phase steering capabilities without any special optimization procedure.

Cumulative minutes with T90 greater than Tempindex is predictive of response of superficial malignancies to hyperthermia and radiation

PURPOSE

To better define thermal parameters related to tumor response in superficial malignancies treated with combined hyperthermia and radiation therapy.

METHODS AND MATERIALS

Patients were randomized to receive one or two hyperthermia treatments per week with hyperthermia given during each week of irradiation. Hyperthermia was given for 60 min with treatments begun within 1 hr following irradiation. Power was increased to patient tolerance or normal tissue temperature of 43.0 degrees C. Irradiation was generally given 5 times per week with doses prescribed to normal tissue tolerance (generally 24-70 Gy at 1.8-2.5 Gy per fraction). Multipoint thermometry was used with temperatures obtained every 5 min.

RESULTS

One hundred eleven individual treatment fields containing 1 or more tumor nodules were completely evaluable. The complete and overall response rates were 46% and 80%, respectively. Forty-one percent of all treatment fields (51% of responding lesions) remained controlled at 2 years. Multivariate analysis revealed that the cumulative minutes that the temperature achieved by 90% of the measured tumor sites (T90) was > or = 40.0 degrees C, tumor histology, tumor volume, and radiation dose were significantly associated with complete tumor response. The complete response rate was not significantly affected by the number of hyperthermia treatments given per week. The incidence of clinically significant complications was low.

CONCLUSIONS

These results support the usefulness of the cumulative minute system in describing time-temperature relationships. The significance of thermal variables with regard to tumor response strongly supports the contention that hyperthermia can be a useful adjunct to irradiation for the local control of cancer.