Tumour perfusion assessment during regional hyperthermia treatment: comparison of temperature probe measurement with H(2)(15)O-PET perfusion.

PURPOSE: Hyperthermia treatment might increase tumour oxygenation and perfusion, as has been reported for experimental tumours. The present study was performed to investigate this hypothesis in patients undergoing regional hyperthermia treatment. METHODS: Thirteen patients with primary or recurrent pelvic tumours were included in this study. Prior to and up to one hour after regional hyperthermia, perfusion was quantitatively determined by H(2)(15)O-PET. The fused CT-PET images were used to extract tumour time-activity curves and to identify the catheter position. Perfusion was calculated from the total tumour time-activity curves and for the time-activity curves at the catheter site. Additionally, perfusion was calculated from the temperature-time curves measured using temperature probes. RESULTS: Perfusion values calculated using H(2)(15)O-PET and those deduced from temperature probe measurements are significantly correlated with a correlation coefficient, R = 0.21. The perfusion values deduced from the temperature measured in a body cavity do not provide information about average tumour perfusion. Perfusion values deduced from the temperature are overestimated for very poorly perfused tissues and underestimated for highly perfused tissues. CONCLUSIONS: Temperature measurement during hyperthermia may allow only determination of intermediate perfusion values.

Radiochemotherapy combined with regional pelvic hyperthermia induces high response and resectability rates in patients with nonresectable cervical cancer > or =FIGO IIB "bulky".

PURPOSE: To evaluate preoperative radiochemotherapy combined with regional pelvic hyperthermia in patients with nonresectable cervical cancer >/= International Federation of Gynecology and Obstetrics (FIGO) IIB "bulky" in a Phase II study. METHODS AND MATERIALS: Thirty-two patients with nonresectable FIGO IIB-IVA cervical cancer confined to the pelvis were treated with radiochemotherapy (5 x 1.8 Gy/wk, 45-50.4 Gy; cisplatin, 40 mg/m2/wk) and weekly regional pelvic hyperthermia (SIGMA-60 applicator, system BSD-2000; BSD Medical Corp., Salt Lake City, UT). Responders underwent hysterectomy if possible, whereas patients still unresectable received definitive hyperthermic radiochemotherapy. Feasibility, toxicity, as well as response and resectability, local progression free- and overall survival rates, were evaluated. RESULTS: Thirty of 32 patients completed treatment. Grade III/IV toxicities (National Cancer Institute-Common Toxicity Criteria) were diarrhea (n = 5), weight loss >10 kg (n = 4), and nausea (n = 2). Twenty-four of 32 patients (75%) achieved a partial remission after 45-50 Gy, and 20 patients underwent hysterectomy (18 patients, R0; 8 patients pCR). Three-year overall survival was 60%, with moderate (13%) rates of severe late toxicity. R0-resected patients had a favorable chronic toxicity profile and an excellent prognosis (3-year survival rate: 93%). Response depended on thermal parameters (vaginal reference point), whereas response, R0-resection, and FIGO stage are significant prognostic factors for survival. CONCLUSION: Preoperative hyperthermic radiochemotherapy (45-50 Gy) induces high response rates and enables curative surgery in a high proportion of patients with nonresectable cervical cancer. Therefore, the use of hyperthermia in conjunction with standard chemo-/radiotherapy +/- surgery may allow for more effective tumor treatment while decreasing the risk of complications in patients with locally advanced cervical cancer.

Dose-escalated conformal radiotherapy of glioblastomas -- results of a retrospective comparison applying radiation doses of 60 and 70 Gy.

BACKGROUND: Dose escalated three-dimensional conformal radiotherapy with 70 Gy against glioblastomas was compared retrospectively with the standard scheme of 60 Gy using 2-D-planning. PATIENTS AND METHODS: In the period from 1994 to 1998, a series of 135 patients with glioblastomas was treated by surgery and postoperative radiotherapy. A conversion from 2-D into 3-D-planning was carried out in 4/1996. The prescribed total dose for the first 65 patients was 60 Gy (group 60). A boost up to 70 Gy was added for the remaining 70 patients (group 70). RESULTS: The median survival time was 8.0 months for group 60 and 8.3 months for group 70. A dependency on the applied dose range was found. The median survival time was 3 months for patients who received a radiation dose of 55 Gy or less, 8.6 months for doses between 56 and 65 Gy, and 9.6 months for patients with a dose between 66 and 75 Gy (p < 0.01). In a multivariate analysis only the performance status maintained significance (p = 0.02) as a prognostic factor, while the dose range reached borderline significance (p = 0.09). CONCLUSION: No statistically significant survival prolongation was reached despite a dose escalation to 70 Gy.

Clinical use of the hyperthermia treatment planning system HyperPlan to predict effectiveness and toxicity.

PURPOSE: The main aim is to prove the clinical practicability of the hyperthermia treatment planning system HyperPlan on a beta-test level. Data and observations obtained from clinical hyperthermia are compared with the numeric methods FE (finite element) and FDTD (finite difference time domain), respectively. METHODS AND MATERIALS: The planning system HyperPlan is built on top of the modular, object-oriented platform for visualization and model generation AMIRA. This system already contains powerful algorithms for image processing, geometric modeling, and three-dimensional graphics display. A number of hyperthermia-specific modules are provided, enabling the creation of three-dimensional tetrahedral patient models suitable for treatment planning. Two numeric methods, FE and FDTD, are implemented in HyperPlan for solving Maxwell's equations. Both methods base their calculations on segmented (contour based) CT or MR image data. A tetrahedral grid is generated from the segmented tissue boundaries, consisting of approximately 80,000 tetrahedrons per patient. The FE method necessitates, primarily, this tetrahedral grid for the calculation of the E-field. The FDTD method, on the other hand, calculates the E-field on a cubical grid, but also requires a tetrahedral grid for correction at electrical interfaces. In both methods, temperature distributions are calculated on the tetrahedral grid by solving the bioheat transfer equation with the FE method. Segmentation, grid generation, E-field, and temperature calculation can be carried out in clinical practice at an acceptable time expenditure of about 1-2 days. RESULTS: All 30 patients we analyzed with cervical, rectal, and prostate carcinoma exhibit a good correlation between the model calculations and the attained clinical data regarding acute toxicity (hot spots), prediction of easy-to-heat or difficult-to-heat patients, and the dependency on various other individual parameters. We could show sufficient agreement between the calculations and measurements for power density (specific absorption rate) within the range of assessed precision. Tumor temperatures can only be estimated, because of the rather variable perfusion conditions. The results of the FE and FDTD methods are comparable, although slight differences exist resulting from the differences in the underlying models. There are also statistically provable differences among the tumor entities regarding the attained specific absorption rate, temperatures, and volume loads in normal tissue. However, gross fluctuations exist from patient to patient. CONCLUSION: The hyperthermia planning system HyperPlan could be validated for a number of the 30 patients. Further improvements in the implemented models, FE and FDTD, are required. Even at its present state of development, hyperthermia planning for regional hyperthermia delivers valuable information, not only for clinical practice, but also for further technologic improvements.

The cellular and molecular basis of hyperthermia.

In oncology, the term 'hyperthermia' refers to the treatment of malignant diseases by administering heat in various ways. Hyperthermia is usually applied as an adjunct to an already established treatment modality (especially radiotherapy and chemotherapy), where tumor temperatures in the range of 40-43 degrees C are aspired. In several clinical phase-III trials, an improvement of both local control and survival rates have been demonstrated by adding local/regional hyperthermia to radiotherapy in patients with locally advanced or recurrent superficial and pelvic tumors. In addition, interstitial hyperthermia, hyperthermic chemoperfusion, and whole-body hyperthermia (WBH) are under clinical investigation, and some positive comparative trials have already been completed. In parallel to clinical research, several aspects of heat action have been examined in numerous pre-clinical studies since the 1970s. However, an unequivocal identification of the mechanisms leading to favorable clinical results of hyperthermia have not yet been identified for various reasons. This manuscript deals with discussions concerning the direct cytotoxic effect of heat, heat-induced alterations of the tumor microenvironment, synergism of heat in conjunction with radiation and drugs, as well as, the presumed cellular effects of hyperthermia including the expression of heat-shock proteins (HSP), induction and regulation of apoptosis, signal transduction, and modulation of drug resistance by hyperthermia.