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.

Definitive chemoradiation for locoregional recurrences of esophageal cancer after primary curative treatment.

The aim of this study was to determine the outcome of salvage definitive chemoradiation (dCRT) for a locoregional recurrence after any prior curative treatment outside previously irradiated areas. Thirty-nine patients treated between January 2005 and December 2014 were reviewed for locoregional recurrent esophageal cancer outside previously irradiated areas. All patients received salvage treatment with external beam radiotherapy (50.4 Gy in 28 fractions) combined with weekly concurrent paclitaxel and carboplatin. The median follow-up period was 15 months (range 1.7-120). The median overall survival (OS) for all patients after salvage dCRT was 22 months (95% CI 6.2-37.6). The 1-, 3-, and 5-year OS was 72%, 31%, and 28%, respectively. Median survival after salvage dCRT for a regional lymph node recurrence was 33 months (95% CI 5.8-60.3) versus 14 months (95% CI 6.8-21.6) for a recurrence at the anastomosis (P = 0.022, logrank). Median OS was 35 months for the squamous cell carcinoma group and 19 months for the adenocarcinoma group (P = 0.67). Sixteen of 39 patients developed a locoregional recurrence after salvaged dCRT. The median locoregional recurrence-free survival (LRFS) was 24 months. The 1-, 3-, and 5-year LRFS was 79%, 36%, and 36%, respectively. Median disease-free survival (DFS) was 15 months. The 1-, 3-, and 5-year DFS was 66%, 27%, and 27%, respectively. Of 16 patients, 8 (50%) with a primary failure at the site of the anastomosis developed a local recurrence after salvaged dCRT compared to 7 of 22 patients (32%) with a primary recurrence in a lymph node. Definitive chemoradiation is a feasible and effective treatment for locoregional recurrent esophageal cancer outside a previously irradiated area, and should be given with a curative intent. This holds true for recurrence of both squamous cell carcinoma and adenocarcinoma. Lymph node recurrences have a markedly better prognosis than recurrences at the site of the anastomosis.

Definitive chemoradiation for patients with inoperable and/or unresectable esophageal cancer: locoregional recurrence pattern.

A locoregional recurrence after definitive chemoradiation (dCRT) for patients with inoperable or unresectable esophageal cancer occurs in about 50% of the patients and is a major cause of failure with a poor prognosis. The aim of this study was to determine the pattern of locoregional recurrence and its prognostic factors after dCRT in order to search for improvements in radiation treatment. We retrospectively reviewed 184 patients treated with external beam radiotherapy (50.4 Gray/28 fractions), combined with weekly concurrent paclitaxel and carboplatin. Locoregional recurrences were defined by clinical signs of recurrent or progressive disease, combined with progression on computed tomography/positron emission tomography-computed tomography scan, or suspicious endoscopic findings and/or histological proof of recurrence. The site of locoregional recurrence was analyzed with respect to the borders of the radiation fields. After a mean follow up of 22.8 months, 76 patients (41%) had evidence of locoregional recurrence. The 3-years locoregional recurrence-free rate was 45%. The majority of locoregional recurrences occurred within 12 months, nearly all within 24 months. The majority of these patients failed at the site of the primary tumor (86%). Infield locoregional recurrences at the site of the lymph nodes only occurred in 1% compared with 57% at the site of the primary tumor only. Outfield locoregional lymph node recurrences occurred in 22%, without infield recurrence occurred in only 4% of all patients. The 1-, 3-, and 5-year overall survival was 65%, 28%, and 21%, respectively. The current analysis demonstrates that a locoregional recurrence after dCRT occurs in 41% of the patients, the majority at the site of the primary tumor. These data suggest a benefit of dose intensification of the primary tumor, but not at the site of the lymph nodes. Higher radiation doses should be assessed with prospective trials.

Diagnostic workup for esophageal cancer patients can be improved with checklists and clearer protocols; a comparative study between two tertiary centers in Europe.

BACKGROUND: Rapid and complete workup of newly diagnosed esophageal cancer is vital for a timely, individual and high-quality treatment strategy. The aim of this study was to uncover potential delay, inefficiencies and non-contributing investigations in the diagnostic process in two tertiary referral centers. METHODS: This retrospective cohort study included all newly diagnosed esophageal cancer patients referred to or diagnosed in the Amsterdam UMC and Karolinska University Hospital between July 2020 and July 2021. Radiology, pathological assessment and multidisciplinary team meeting reports were reviewed. To assess time interval from diagnosis to treatment, dates of diagnosis, admittance to referral hospital, MDT meeting and start of treatment were collected. RESULTS: In total, 252 esophageal cancer patients were included, 187 were treated with curative intent. Curatively treated patients had a mean age of 66 years, were predominantly male (74.9 %) with an adenocarcinoma (71.1 %). Curatively treated patients had a median time from diagnosis to referral of seven days (IQR:0-11) and of 35 days (IQR:28-45) between diagnosis and start of treatment. Main reasons for the significant (P < 0.001) differences in time between diagnosis and treatment between centers, Amsterdam UMC (39 days) vs Karolinska (27 days), were need for additional diagnostics (47.8 %) and differences in referral routine. Gastroscopy was repeated in 32.2 % of patients, mainly for further anatomical mapping. CONCLUSION: Significant time differences between centers in the path from diagnosis to start treatment can be explained by differences in workup approach, referral routines and MDT meeting regulations. Repeat of gastroscopy can be prevented with clearer endoscopy guidelines.

Effect of a prediction tool and communication skills training on communication of treatment outcomes: a multicenter stepped wedge clinical trial (the SOURCE trial).

Background: For cancer patients to effectively engage in decision making, they require comprehensive and understandable information regarding treatment options and their associated outcomes. We developed an online prediction tool and supporting communication skills training to assist healthcare providers (HCPs) in this complex task. This study aims to assess the impact of this combined intervention (prediction tool and training) on the communication practices of HCPs when discussing treatment options. Methods: We conducted a multicenter intervention trial using a pragmatic stepped wedge design (NCT04232735). Standardized Patient Assessments (simulated consultations) using cases of esophageal and gastric cancer patients, were performed before and after the combined intervention (March 2020 to July 2022). Audio recordings were analyzed using an observational coding scale, rating all utterances of treatment outcome information on the primary outcome-precision of provided outcome information-and on secondary outcomes-such as: personalization, tailoring and use of visualizations. Pre vs. post measurements were compared in order to assess the effect of the intervention. Findings: 31 HCPs of 11 different centers in the Netherlands participated. The tool and training significantly affected the precision of the overall communicated treatment outcome information (p = 0.001, median difference 6.93, IQR (-0.32 to 12.44)). In the curative setting, survival information was significantly more precise after the intervention (p = 0.029). In the palliative setting, information about side effects was more precise (p < 0.001). Interpretation: A prediction tool and communication skills training for HCPs improves the precision of treatment information on outcomes in simulated consultations. The next step is to examine the effect of such interventions on communication in clinical practice and on patient-reported outcomes. Funding: Financial support for this study was provided entirely by a grant from the Dutch Cancer Society (UVA 2014-7000).

Impaired Geriatric 8 Score is Associated with Worse Survival after Radiotherapy in Older Patients with Cancer.

AIMS: To investigate whether the Geriatric 8 (G8) score and the Timed Get Up and Go Test (TGUGT), together with clinical and demographic patient characteristics, are associated with survival and late toxicity after (chemo)radiation therapy, administered with curative intent in older patients with cancer. MATERIALS AND METHODS: Four hundred and two patients aged ≥65 years (median age 72 years, range 65-96 years), diagnosed with either breast, non-small cell lung, prostate, head and neck, rectal or oesophageal cancer, and referred for curative (chemo)radiation therapy, took part in a multicentre prospective cohort study in eight radiotherapy centres in the Netherlands. The G8 and TGUGT scores were assessed before starting treatment. Other potential predictors and late toxicity were also recorded. Survival status and date of death, if applicable, were ascertained at the Dutch national death registry. RESULTS: After 2.5 years, the overall survival was 83%. Survival was 87% for patients with high G8 scores and 55% for patients with low G8 scores (Log-rank P value < 0.0001). Survival was 77% for patients with good TGUGT results and 50% for patients with poor TGUGT results (Log-rank P value < 0.001). In multivariable analysis, in addition to age and type of primary tumour, the association of the G8 score with overall survival remained, with a hazard ratio of 2.1 (95% confidence interval 1.2-3.8) for low versus high scores. CONCLUSIONS: G8 was associated with overall survival in older patients with cancer irradiated with curative intent. This association was independent of the predictive value of age and primary tumour.

Neoadjuvant Chemoradiotherapy Combined with Atezolizumab for Resectable Esophageal Adenocarcinoma: A Single-arm Phase II Feasibility Trial (PERFECT).

PURPOSE: The CROSS trial established neoadjuvant chemoradiotherapy (nCRT) for patients with resectable esophageal adenocarcinoma (rEAC). In the PERFECT trial, we investigated the feasibility and efficacy of nCRT combined with programmed-death ligand-1 (PD-L1) inhibition for rEAC. PATIENTS AND METHODS: Patients with rEAC received nCRT according to the CROSS regimen combined with five cycles of atezolizumab (1,200 mg). The primary endpoint was the feasibility of administering five cycles of atezolizumab in ≥75% patients. A propensity score-matched nCRT cohort was used to compare pathologic response, overall survival, and progression-free survival. Exploratory biomarker analysis was performed on repeated tumor biopsies. RESULTS: We enrolled 40 patients of whom 85% received all cycles of atezolizumab. Immune-related adverse events of any grade were observed in 6 patients. In total, 83% proceeded to surgery. Reasons for not undergoing surgery were progression (n = 4), patient choice (n = 2), and death (n = 1). The pathologic complete response rate was 25% (10/40). No statistically significant difference in response or survival was found between the PERFECT and the nCRT cohort. Baseline expression of an established IFNγ signature was higher in responders compared with nonresponders (P = 0.043). On-treatment nonresponders showed either a high number of cytotoxic lymphocytes (CTL) with a transcriptional signature consistent with expression of immune checkpoints, or a low number of CTLs. CONCLUSIONS: Combining nCRT with atezolizumab is feasible in patients with rEAC. On the basis of our exploratory biomarker study, future studies are necessary to elucidate the potential of neoadjuvant immunotherapy in patient subgroups.See related commentary by Catenacci, p. 3269.

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.

Online adaptive radiotherapy compared to plan selection for rectal cancer: quantifying the benefit.

BACKGROUND: To compare online adaptive radiation therapy (ART) to a clinically implemented plan selection strategy (PS) with respect to dose to the organs at risk (OAR) for rectal cancer. METHODS: The first 20 patients treated with PS between May-September 2016 were included. This resulted in 10 short (SCRT) and 10 long (LCRT) course radiotherapy treatment schedules with a total of 300 Conebeam CT scans (CBCT). New dual arc VMAT plans were generated using auto-planning for both the online ART and PS strategy. For each fraction bowel bag, bladder and mesorectum were delineated on daily Conebeam CTs. The dose distribution planned was used to calculate daily DVHs. Coverage of the CTV was calculated, as defined by the dose received by 99% of the CTV volume (D99%). The volume of normal tissue irradiated with 95% of the prescribed fraction dose was calculated by calculating the volume receiving 95% of the prescribed fraction or more dose minus the volume of the CTV. For each fraction the difference between the plan selection and online adaptive strategy of each DVH parameter was calculated, as well as the average difference per patient. RESULTS: Target coverage remained the same for online ART. The median volume of the normal tissue irradiated with 95% of the prescribed dose dropped from 642 cm3 (PS) to 237 cm3 (online-ART)(p < 0.001). Online ART reduced dose to the OARs for all tested dose levels for SCRT and LCRT (p < 0.001). For V15Gy of the bowel bag the median difference over all fractions of all patients was - 126 cm3 in LCRT, while the average difference per patient ranged from - 206 cm3 to - 40 cm3. For SCRT the median difference was - 62 cm3, while the range of the average difference per patient was - 105 cm3 to - 51 cm3. For V15Gy of the bladder the median difference over all fractions of all patients was 26% in LCRT, while the average difference per patient ranged from - 34 to 12%. For SCRT the median difference of V95% was - 8%, while the range of the average difference per patient was - 29 to 0%. CONCLUSIONS: Online ART for rectal cancer reduces dose the OARs significantly compared to a clinically implemented plan selection strategy, without compromising target coverage. TRIAL REGISTRATION: Medical Research Involving Human Subjects Act (WMO) does not apply to this study and was retrospectively approved by the Medical Ethics review Committee of the Academic Medical Center (W19_357 # 19.420; Amsterdam University Medical Centers, Location Academic Medical Center, Amsterdam, The Netherlands).

Dosimetric benefit of an adaptive treatment by means of plan selection for rectal cancer patients in both short and long course radiation therapy.

BACKGROUND: To compare target coverage and dose to the organs at risk in two approaches to rectal cancer: a clinically implemented adaptive radiotherapy (ART) strategy using plan selection, and a non-adaptive (non-ART) strategy. METHODS: The inclusion of the first 20 patients receiving adaptive radiotherapy produced 10 patients with a long treatment schedule (25x2Gy) and 10 patients with a short schedule (5X5Gy). We prepared a library of three plans with different anterior PTV margins to the upper mesorectum, and selected the most appropriate plan on daily Conebeam CT scans (CBCT). We also created a non-adaptive treatment plan with a 20 mm margin. Bowel bag, bladder and target volume were delineated on CBCT. Daily DHVs were calculated based on the dose distribution of the selected and non-adaptive plans. Coverage of the target volume was compared per fraction between the ART and non-ART plans, as was the dose to the bladder and small bowel, assessing the following dose levels: V15Gy, V30Gy, V40Gy, V15Gy and V95% for long treatment schedules, and V15Gy and V95% for short ones. RESULTS: Target volume coverage was maintained from 98.3% (non-ART) to 99.0% (ART)(p = 0.878). In the small bowel, ART appeared to have produced significant reductions in the long treatment schedule at V15Gy, V40Gy, V45Gy and V95% (p <  0.05), but with small absolute differences. The DVH parameters tested for the short treatment schedule did not differ significantly. In the bladder, all DVH parameters in both schedules showed significant reductions (p <  0.05), also with small absolute differences. CONCLUSIONS: The adaptive treatment maintained target coverage and reduced dose to the organs at risk. TRIAL REGISTRATION: Medical Research Involving Human Subjects Act (WMO) does not apply to this study and was retrospectively approved by the Medical Ethics review Committee of the Academic Medical Center, W19_194 # 19.233.

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.

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.

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.