The effect of air pockets in the urinary bladder on the temperature distribution during loco-regional hyperthermia treatment of bladder cancer patients.

PURPOSE: Loco-regional hyperthermia combined with mitomycin C is used for treatment of nonmuscle invasive bladder cancer (NMIBC). Air pockets may be present in the bladder during treatment. The aim of this study is to quantify the effect of air pockets on the thermal dose of the bladder. METHODS: We analysed 16 patients treated for NMIBC. Loco-regional hyperthermia was performed with the in-house developed 70 MHz AMC-4 hyperthermia device. We simulated treatments with the clinically applied device settings using Plan2Heat (developed in-house) including the air pockets delineated on CT scans made following treatment, and with the same volume filled with urine. Temperature distributions simulated with and without air pockets were compared. RESULTS: The average air and fluid volumes in the bladder were 6.0 ml (range 0.8 - 19.3 ml) and 183 ml (range 47-322 ml), respectively. The effect of these air pockets varied strongly between patients. Averaged over all patients, the median bladder wall temperature (T50) remained unchanged when an air pocket was present. Temperature changes exceeded ±0.2 °C in, on average, 23% of the bladder wall volume (range 1.3-59%), in 6.0% (range 0.6-20%) changes exceeded ±0.5 °C and in 3.2% (range 0.0-7.4%) changes exceeded ±1.0 °C. There was no correlation between the differences in temperature and the air pocket or bladder volume. There was a positive correlation between air pocket surface and temperature heterogeneity. CONCLUSION: Presence of air causes more heterogeneous bladder wall temperatures and lower T90, particularly for larger air pockets. The size of air pockets must therefore be minimized during bladder hyperthermia treatments.

Predictive value of simulated SAR and temperature for changes in measured temperature after phase-amplitude steering during locoregional hyperthermia treatments.

INTRODUCTION: On-line adaptive hyperthermia treatment planning can be useful to suppress treatment limiting hot spots and improve tumor temperatures during locoregional hyperthermia. This requires adequate prediction of changes in heating patterns after phase-amplitude steering. We investigated the predictive value of simulated SAR and temperature for changes in measured temperature after phase-amplitude steering during locoregional hyperthermia. METHODS: All treatment sessions of 75 patients with pelvic malignancies treated between September 2013 and March 2018 were evaluated. Phase-amplitude adaptations during the 60 min steady-state period were analyzed. Treatment planning was performed using Plan2Heat, based on CT scans with (thermometry) catheters in the vagina, rectum, and bladder in situ. The predicted SAR and temperature along the thermometry tracks were extracted from the simulated distributions. Correlations between changes in average measured temperature and the simulated SAR and temperature were evaluated for single phase-amplitude steering events, unaccompanied by other (steering) actions. RESULTS: A total of 67 phase-amplitude steering events were suitable for analysis. Simulated changes in both SAR and temperature correlated with the measured temperature changes. For the vagina, R2 = 0.44 and R2 = 0.55 for SAR and temperature, respectively. For the rectum, these values were 0.53 for SAR and 0.66 for temperature. Correlations for the bladder were weaker: R2 = 0.15 and R2 = 0.14 for SAR and temperature, respectively. This can be explained by convection in the bladder fluid, unaccounted for by present treatment planning. CONCLUSION: Treatment planning can predict changes in an average temperature after phase-amplitude steering. This allows on-line support with phase-amplitude steering to optimize hyperthermia treatments.

Improving hyperthermia treatment planning for the pelvis by accurate fluid modeling.

PURPOSE: Hyperthermia is an established (neo)adjuvant treatment modality for a number of pelvic malignancies. Optimal treatment of these tumors requires robust treatment planning, but up until now, the urinary bladder was not modeled accurately, making current simulations less reliable. The authors improved the dielectric and thermophysical model of the urinary bladder in their treatment planning system, and showed the improvements using phantom experiments. METHODS: The authors suspended a porcine bladder in muscle tissue equivalent gel and filled it with 120 ml 0.9% saline. The authors heated the phantom during 15 min with their deep hyperthermia device, using clinical settings, and measured the temperature both inside and outside the bladder. The authors simulated the experiment, both using the clinically used treatment planning system, and using the improved model featuring correct dielectric properties for the bladder content and an enhanced thermophysical model, enabling the simulation of convection. RESULTS: Although the dielectric changes have an impact throughout the phantom, the dominant effect is a higher net heat absorption in the bladder. The effects of changing the thermophysical model are limited to the bladder and its surroundings, but result in a very different temperature profile. The temperatures predicted by the simulations using the new bladder model were in much better agreement with the measurements than those predicted by currently used treatment planning system. CONCLUSIONS: Modeling convection in the urinary bladder is very important for accurate hyperthermia treatment planning in the pelvic area.

Radiotherapy combined with hyperthermia for primary malignant melanomas of the esophagus.

Primary malignant melanoma of the esophagus (PMME) forms about 0.1% of all primary esophageal cancers. Treatment options are very limited for patients unfit for surgery. This is the first report describing the results of external radiotherapy combined with regional hyperthermia for two inoperable PMME patients. Two patients with a T2-3N0M0 PMME were considered unfit for surgery based on age and general condition. External radiotherapy of a total dose of 35 Gy was given in a scheme of seven times 5 Gy, two times per week, and once weekly combined with external and intraluminal hyperthermia (aim 43°C). Toxicity was mild and both patients completed treatment according to protocol. Adequate temperatures at the intraluminal border of the tumor were achieved. In both patients, a complete remission was achieved with complete relief of obstructive symptoms and without signs of locoregional tumor progression until the end of follow-up at 11 and 15 months. External radiation combined with regional hyperthermia could be a good alternative to resection in patients unfit for surgery with a malignant melanoma of the esophagus.

Preoperative chemoradiation combined with regional hyperthermia for patients with resectable esophageal cancer.

PURPOSE: To analyse the treatment results of neo-adjuvant chemoradiation combined with regional hyperthermia in patients with resectable esophageal cancer. PATIENTS AND METHODS: Between August 2003 and December 2004, 28 patients entered a phase II study combining chemoradiation over a 4.5-week period with five sessions of regional hyperthermia. Chemotherapy consisted of carboplatin (AUC = 2) and paclitaxel (50 mg/m(2)) and radiotherapy of 41.4 Gy in 1.8 Gy daily fractions. Locoregional hyperthermia was applied using the AMC phased array of four 70 MHz antennas, aiming at a stable tumor temperature of 41 degrees C for one hour. Carboplatin was infused during the hyperthermia session. Esophageal resection was planned at 6-8 weeks after the end of radiotherapy. The majority of the patients had a T3 tumor (86%) and were cN+ (64%). Median follow-up for survivors was 37 months (range 31-46). RESULTS: Twenty-five patients (89%) completed the planned neo-adjuvant treatment and acute toxicity was generally mild. Twenty-six patients were operated on. A pathologically CR, PRmic, PR and SD were seen in 19%, 27%, 31% and 23% respectively. All patients had a R0 resection. In-field locoregional control during follow up for the operated patients was 100%. Quality of life was good for patients without disease progression. Survival rates at one, two and three years were 79%, 57% and 54% respectively. CONCLUSION: Neo-adjuvant chemoradiation combined with regional hyperthermia followed by esophageal resection for patients with esophageal cancer resulted in good locoregional control and overall survival.

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

PURPOSE: To analyse the relation between patients' body size and temperatures during locoregional hyperthermia for oesophageal cancer. METHODS: Patients were treated with neo-adjuvant chemoradiotherapy plus hyperthermia, given with the AMC-4 waveguide system. Temperatures were measured at tumour location in the oesophageal lumen using multisensor thermocouple probes. Systemic temperature rise (DeltaT(syst)) was monitored rectally. Steady-state tumour temperatures were expressed in terms of T(90), T(50) and T(10), averaged over the five hyperthermia sessions, and correlated with patients' body mass, dorsoventral and lateral diameter and fat layer thickness, measured at tumour level using a CT scan made in treatment position. Fat percentage (Fat%) was estimated using diameters and fat layer thickness. Effective tumour perfusion (W(b)) was estimated from the temperature decay during the cool-down period. RESULTS: Temperatures were inversely related to body mass, diameters, fat layer thickness, and fat percentage. The strongest univariate correlations were found with lateral fat layer thickness, lateral diameter, and body mass. An increase in lateral diameter (28-->42 cm), or in lateral fat layer thickness (0-->40 mm) or in body mass (50-->120 kg) all yielded a approximately 1.5 degrees C decrease in tumour temperature rise. Multivariate correlation analysis proved that the combination of Fat%, DeltaT(syst) and W(b) was most predictive for the achieved tumour temperatures, accounting for 81 +/- 12% of the variance in temperatures. CONCLUSIONS: Intra-oesophageal temperatures during locoregional hyperthermia are inversely related to patients' body size parameters, of which fat percentage is the most significant prognostic factor. These findings could be used to define inclusion criteria of new studies on intrathoracic hyperthermia.

Hyperthermia, cisplatin and radiation trimodality treatment: a promising cancer treatment? A review from preclinical studies to clinical application.

This review discusses available clinical and experimental data and the underlying mechanisms involved in trimodality treatment consisting of hyperthermia, cisplatin and radiotherapy. The results of phase I/II clinical trials show that trimodality treatment is effective and feasible in various cancer types and sites with tolerable toxicity. Based on these results, phase III trials have been launched to investigate whether significant differences in treatment outcome exist between trimodality and standard treatment. In view of the clinical interest, it is surprising to find so few preclinical studies on trimodality treatment. Although little information is available on the doses of the modalities and the treatment sequence resulting in the largest degree of synergistic interaction, the results from in vivo and in vitro preclinical studies support the use of trimodality treatment for cancer patients. Animal studies show an improvement in treatment outcome after trimodality treatment compared with mono- and bimodality treatment. Studies in different human tumour cell lines show that a synergistic interaction can be obtained between hyperthermia, cisplatin and radiation and that this interaction is more likely to occur in cell lines which are more sensitive to cisplatin.

Prospective treatment planning to improve locoregional hyperthermia for oesophageal cancer.

BACKGROUND: In the Academic Medical Center (AMC) Amsterdam, locoregional hyperthermia for oesophageal tumours is applied using the 70 MHz AMC-4 phased array system. Due to the occurrence of treatment-limiting hot spots in normal tissue and systemic stress at high power, the thermal dose achieved in the tumour can be sub-optimal. The large number of degrees of freedom of the heating device, i.e. the amplitudes and phases of the antennae, makes it difficult to avoid treatment-limiting hot spots by intuitive amplitude/phase steering. AIM: Prospective hyperthermia treatment planning combined with high resolution temperature-based optimization was applied to improve hyperthermia treatment of patients with oesophageal cancer. METHODS: All hyperthermia treatments were performed with 'standard' clinical settings. Temperatures were measured systemically, at the location of the tumour and near the spinal cord, which is an organ at risk. For 16 patients numerically optimized settings were obtained from treatment planning with temperature-based optimization. Steady state tumour temperatures were maximized, subject to constraints to normal tissue temperatures. At the start of 48 hyperthermia treatments in these 16 patients temperature rise (DeltaT) measurements were performed by applying a short power pulse with the numerically optimized amplitude/phase settings, with the clinical settings and with mixed settings, i.e. numerically optimized amplitudes combined with clinical phases. The heating efficiency of the three settings was determined by the measured DeltaT values and the DeltaT-ratio between the DeltaT in the tumour (DeltaToes) and near the spinal cord (DeltaTcord). For a single patient the steady state temperature distribution was computed retrospectively for all three settings, since the temperature distributions may be quite different. To illustrate that the choice of the optimization strategy is decisive for the obtained settings, a numerical optimization on DeltaT-ratio was performed for this patient and the steady state temperature distribution for the obtained settings was computed. RESULTS: A higher DeltaToes was measured with the mixed settings compared to the calculated and clinical settings; DeltaTcord was higher with the mixed settings compared to the clinical settings. The DeltaT-ratio was approximately 1.5 for all three settings. These results indicate that the most effective tumour heating can be achieved with the mixed settings. DeltaT is proportional to the Specific Absorption Rate (SAR) and a higher SAR results in a higher steady state temperature, which implies that mixed settings are likely to provide the most effective heating at steady state as well. The steady state temperature distributions for the clinical and mixed settings, computed for the single patient, showed some locations where temperatures exceeded the normal tissue constraints used in the optimization. This demonstrates that the numerical optimization did not prescribe the mixed settings, because it had to comply with the constraints set to the normal tissue temperatures. However, the predicted hot spots are not necessarily clinically relevant. Numerical optimization on DeltaT-ratio for this patient yielded a very high DeltaT-ratio ( approximately 380), albeit at the cost of excessive heating of normal tissue and lower steady state tumour temperatures compared to the conventional optimization. CONCLUSION: Treatment planning can be valuable to improve hyperthermia treatments. A thorough discussion on clinically relevant objectives and constraints is essential.