Temporal changes in tumor oxygenation and perfusion upon normo- and hyperbaric inspiratory hyperoxia.

BACKGROUND: Inspiratory hyperoxia under hyperbaric conditions has been shown to effectively reduce tumor hypoxia and to improve radiosensitivity. However, applying irradiation (RT) under hyperbaric conditions is technically difficult in the clinical setting since RT after decompression may be effective only if tumor pO2 remains elevated for a certain period of time. The aim of the present study was to analyze the time course of tumor oxygenation and perfusion during and after hyperbaric hyperoxia. MATERIALS AND METHODS: Tumor oxygenation, red blood cell (RBC) flux for perfusion monitoring, and vascular resistance were assessed continuously in experimental rat DS-sarcomas by polarographic catheter electrodes and laser Doppler flowmetry at 1 and 2 atm (bar) of environmental pressure during breathing of pure O2 or carbogen (95 % O2 + 5 % CO2). RESULTS: During room air breathing, the tumor pO2 followed very rapidly within a few minutes the change of the ambient pressure during compression or decompression. With O2 breathing under hyperbaric conditions, the tumor pO2 increased more than expected based on the rise of the environmental pressure, although the time course was comparably rapid. Breathing carbogen, the tumor pO2 followed with a slight delay of the pressure change, and within 10 min after decompression the baseline values were reached again. RBC flux increased during carbogen breathing but remained almost constant with pure O2, indicating a vasodilation (decrease in vascular resistance) with carbogen but a vasoconstriction (increase in vascular resistance) with O2 during hyperbaric conditions. CONCLUSION: Since the tumor pO2 directly followed the environmental pressure, teletherapy after hyperbaric conditions does not seem to be promising as the pO2 reaches baseline values again within 5-10 min after decompression.

Antioxidant potential, in vitro cytotoxicity and apoptotic effect induced by crude organic extract of Anthracophyllum lateritium against RD sarcoma cells.

BACKGROUND: Macrofungi have an established history of use in traditional oriental medicine. Anthracophyllum lateritium is a terrestrial macrofungus found in the dry zone forest reserves in Sri Lanka. Yet there are no scientific reports on bioactive properties of this species. Hence, the current study was aimed at determining the antioxidant potential, in vitro antiproliferative activity and apoptotic effect induced by crude methanolic extract of A. lateritium against RD sarcoma cell line. METHOD: The crude extract of A. lateritium was dissolved in methanol (MEFCA) and antioxidant activity was evaluated using in vitro assays: inhibition of DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging, ferric ion reducing power and 2-deoxy-D-ribose degradation assay. Total phenol and flavonoid contents of MEFCA were assayed using folin Ciocalteu method and aluminium chloride colorimetric method. In vitro cytotoxicity was determined using MTT assay against RD cells after 24 h exposure to MEFCA. Ethidium bromide/ acridine orange staining, DNA fragmentation and protein synthesis experiments were used to study the apoptotic features and antiproliferative activities of the treated cells. Glutathione assay and griess nitrite assay were used to analyze the reduced glutathione content and liberation of nitric oxide from apoptotic cells. RESULTS: MEFCA showed promising antioxidant activity with EC50 values of 8.00 ± 0.35 µg/mL for DPPH scavenging and 83.33 ± 0.45 µg/mL for 2-deoxy-D-ribose degradation assay. The phenolic content was 265.15 ± 0.46 of (w/w) % of Gallic acid equivalents and flavonoid content was 173.01 ± 0.35 of (w/w) % of Epigallocatechingallate. A. lateritium showed strong in vitro cytotoxic activity with an EC50 of 18.80 ± 4.83 µg/mL for MTT assay against RD cells. Ethidium bromide/acridine orange staining and DNA fragmentation indicated the apoptotic features of treated cells. Protein levels showed a dose dependent decrease supporting the fact that A. lateritium induces apoptosis of treated cells. Glutathione content and nitric oxide content of cells exhibited a dose dependent increase suggesting the apoptosis of RD cells was mediated by both nitrie ions and nitric oxide. CONCLUSIONS: The crude extract of the A. lateritium exhibited potent antioxidant, antiproliferative activity and apoptotic effect against RD cells providing supportive evidence for the ethnopharmacological use of this fungus in control of oxidative damage and remedy of cancer.

Sarcomas mandibulares: experiencia quirúrgica en los últimos 10 años / Mandibular sarcomas: surgical experience over the past 10 years

Introducción: Los sarcomas mandibulares representan una entidad de difícil estudio por su escasa incidencia e histopatología. Pacientes y métodos: Presentamos la experiencia del servicio de Cirugía Oral y Maxilofacial del Hospital Vall d’Hebron de Barcelona en los últimos 10 años (2001-2010) en el manejo de los sarcomas mandibulares, realizando una revisión retrospectiva de 12 casos de pacientes afectos por este tipo de tumor. Resultados: La técnica más utilizada para la reconstrucción fue el colgajo microvascularizado (hueso peroné: 8/12), recibiendo tratamiento adyuvante (quimioterapia y/o radioterapia) el 82% de los pacientes. Cinco pacientes fallecieron (42%), 2 se encuentran con progresión de la enfermedad (16%) y 5 sobreviven libres de enfermedad (42%) hasta la finalización del seguimiento. Conclusiones: Los casos descritos representan una serie singular debido a la localización mandibular, no antes publicadas en la literatura. Aún así, los resultados obtenidos en términos de supervivencia y factores pronóstico son similares a los descritos para los sarcomas de cabeza y cuello. La consecución de márgenes libres con la cirugía es la clave del tratamiento, siendo necesario el tratamiento complementario para mejorar el pronóstico(AU)

Introduction: Sarcomas located in the mandible are difficult to study due to their relatively rare appearance and histology. Patients and Methods: We present the experience of the Oral and Maxillofacial Surgery Department of the Vall d’Hebron Hospital in Barcelona over the last 10 years (2001-2010) in the management of jaw sarcomas, performing a retrospective review of 12 cases of patients affected by this type of tumour. Results: The technique mostly used for the reconstruction was the microvascularised bone graft (fibula: 8/12), with 82% of the patients receiving adjuvant therapy (chemotherapy and radiotherapy). Five of the patients died (42%), twowere found with disease progression (16%), and 5 survived free of disease (42%) until the end of follow-up. Conclusions: The cases described are a unique series due to the mandibular location. Prognostic factors and survival rates are similar to those described for head and neck sarcomas. Free margin during surgery must be the goal of treatment, additional chemotherapy or radiotherapy or both being required to improve the survival rates(AU)

Whole body hyperthermia by extracorporeal circulation in spontaneously breathing sarcoma patients: hemodynamics and oxygen metabolism.

PURPOSE: This phase I study was performed to evaluate the feasibility and toxicity of a new method of extracorporeal perfusion-induced whole body hyperthermia (WBHT) in patients with advanced sarcoma avoiding the need of intubation and general anesthesia. METHODS: One double-lumen femoral venous access was inserted by Seldinger's technique to obtain WBHT (41.8°C for 120 minutes) via an extracorporeal circuit. No concomitant chemotherapy was applied. Up to 4 treatments of WBHT were performed under moderate sedation in 6 spontaneously breathing patients. Invasive hemodynamic monitoring was performed by use of a pulmonary artery catheter. RESULTS: After their first WBHT session, 2 patients were excluded from further treatment due to transient liver toxicity or catheter-related complication, so a total of 12 cycles remained for analyses. In all patients, conscious sedation resulted in sufficient spontaneous respiration without the need for mandatory ventilation. Median time to reach the target temperature was 84 minutes (range 60-142). Hemodynamic changes revealed the expected hyperdynamic state: heart rate, cardiac index, and stroke volume index significantly increased (p<0.05), whereas blood pressure and systemic and pulmonary vascular resistance index significantly decreased (p<0.05). A net fluid balance of 5822±1766 mL as well as norepinephrine (mean; 0.062 µg·kg¹·min⁻¹) were necessary to maintain the mean arterial blood pressure >60 mmHg. CONCLUSION: Our data demonstrate the feasibility of this method of extracorporeal WBHT without mandatory ventilation. Hemodynamic side effects in spontaneously breathing patients during perfusion-induced WBHT seem less severe than those observed in radiant heat WBHT.

Immunomodulatory and antitumor activities of grape seed proanthocyanidins.

Proanthocyanidins are naturally occurring compounds that are widely available in many kinds of plants; particularly, the grape seeds are a rich source of proanthocyanidins. Grape seed proanthocyanidins (GSPs) have been demonstrated to possess a wide range of health beneficial properties. This study was carried out to elucidate the molecular mechanisms involved in the antitumor therapeutic and immunomodulating effects of GSPs through in vivo and in vitro models. The results showed that GSPs could significantly inhibit the growth of Sarcoma 180 tumor cells in vivo and remarkably increase thymus and spleen weight of Sarcoma 180-bearing mice and upgrade the secretion level of tumor necrosis factor-α (TNF-α) in serum. Moreover, GSPs could stimulate lymphocyte transformation, enhance lysosomal enzyme activity and phagocytic capability of peritoneal macrophages, and remarkably promote the production of TNF-α. These results suggested that GSPs could improve functional activation of the immune system, and the antitumor effects of GSPs were achieved by immunostimulating properties.

Palifosfamide, a bifunctional alkylator for the treatment of sarcomas.

Ifosfamide is a chemotherapeutic prodrug used in the treatment of several tumor entities, including bone and soft-tissue sarcoma. However, the application of high-dose ifosfamide is not feasible because of severe side effects caused by metabolites. The active metabolite isophosphoramide mustard is not suitable for administration because of chemical instability. ZIOPHARM Oncology Inc, under license from Dekk-Tec Inc, is developing palifosfamide, a formulation of isophosphoramide mustard with tris(hydroxymethyl)aminomethane salt-stabilization (palifosfamide-tris) and previously with lysine-stabilization (palifosfamide-lys). Preclinical studies and phase I and I/II clinical trials demonstrated that palifosfamide-tris had an antitumor efficiency comparable or superior to that of ifosfamide. Patients treated with palifosfamide-tris did not display any of the neurotoxic or nephrotoxic side effects associated with ifosfamide. At the time of publication, data from phase II trials were being evaluated and phase III trials were being planned. palifosfamide-tris is expected to be a safer and less toxic alternative to ifosfamide; however, considering other new approaches under investigation for tumors such as sarcoma, such as molecular-based treatment strategies, it is unclear what position palifosfamide-tris might occupy on the market.

Hyperthermia as an adjunctive treatment for soft-tissue sarcoma.

The treatment for high-risk soft-tissue sarcomas (STSs) in adults remains a challenge for the multidisciplinary approach. Despite aggressive local treatment, high-risk STSs have a tendency for hematogenous spread, which is related, for each histologically distinct sarcoma, to risk factors, such as pathologic grade, size and location. The multimodality approach focuses on the combination of radiochemotherapy in a neoadjuvant or adjuvant setting, surgery being considered the mainstay of local treatment. Therefore, current clinical research aims include preoperative treatment to control systemic microscopic disease and to downsize the primary tumor mass. Within the past 20 years, the application of hyperthermia has been integrated in multimodal treatment strategies in several forms of advanced malignant tumors, as well as in STSs. Hyperthermia is of clinical interest in the temperature range of 40-43 degrees C. Higher temperatures of 44-46 degrees C are not clinically realistic. The rationale for the combination of cytotoxic drugs with regional hyperthermia in the treatment of STS is based upon experimental and clinical evidence that heat increases the killing of tumor cells by direct thermal toxicity and enhances the efficacy of some drugs, such as alkylating agents and platinum analogs. Moreover, recent results show that hyperthermia may be able to modulate the immune system by inducing the expression of heat-shock proteins. The approach of multimodality treatment in STS has used regional hyperthermia with systemic chemotherapy within a preoperative and postoperative strategy. The synergistic effect of hyperthermia with chemotherapy is also used in locoregional treatments, such as isolated limb perfusion and intraperitoneal chemotherapy.

Noninvasive magnetic resonance thermography of soft tissue sarcomas during regional hyperthermia: correlation with response and direct thermometry.

BACKGROUND: The objective of this study was to evaluate noninvasive magnetic resonance (MR) thermography for the monitoring of regional hyperthermia (RHT) in patients with soft tissue sarcomas of the lower extremities and pelvis. METHODS: Noninvasive MR monitoring during RHT was performed in 9 patients who had high-risk soft tissue sarcomas of the lower extremities or pelvis during neoadjuvant chemotherapy plus RHT in the scope of the European Organization for Research and Treatment of Cancer 62961/European Society for Hyperthermic Oncology RHT-95 study. Anatomic and temperature-sensitive data sets were acquired every 10 minutes before and during RHT (using gradient-echo-sequences with variable echo times). MR temperature distributions were derived from the phase differences by using the proton-resonance frequency shift method. A phase convolution setting phase shifts to zero in the fat tissue was performed as a drift correction. The mean MR temperatures in the tumor and muscles and the index temperatures (e.g., T90, which covers 90% of the target volume) and thermal doses were determined and compared with pathohistologic responses and direct temperature measurements if available. RESULTS: Thirty of 72 MR-thermography data sets (>40% of heat sessions) were evaluable. A significant correlation was observed between pathohistologic response (defined as a necrosis rate >or=90%) and standardized thermal parameters, such as thermal dose cumulative equivalent minutes at 43 degrees C to 90% of the target volume (T90) (P = .050), mean T90 (P = .048), or T50 (P = .050). The correlation of 13 conventional temperature measurements performed in selected patients and sessions invasively in the tumor or noninvasively in rectum and bladder revealed an excellent correlation with MR temperatures (R2 = .96). CONCLUSIONS: Noninvasive MR thermography of soft tissue sarcoma was feasible and suitable for validating the quality of heating during RHT.

Inhibition of chemical carcinogenesis by berberine in rats and mice.

Berberine, an alkaloid isolated from the plant Berberis aristata, has been found to inhibit significantly the carcinogenesis induced by 20-methylcholanthrene (200 microg/0.1 mL/mouse) or N-nitrosodiethylamine (NDEA; 0.02% NDEA in distilled water, 2.5 mL/animal by gavage, five days a week for 20 weeks) in a dose-dependent manner in small animals. Administration of berberine (0.5, 2.5 or 5.0 mg kg(-1)) could reduce significantly the incidence of tumour in animals after an injection of 20-methylcholanthrene and increased their life span compared with the control. When berberine (10, 25 or 50 mg kg(-1)) was administered simultaneously with NDEA, the markers of liver injury (liver weight, gamma-glutamyl transpeptidase activity and glutathione S-transferase level) were reduced significantly compared with animals treated with NDEA only, which resulted in all the values being elevated. A similar decrease was noted in the serum levels of lipid peroxide, bilirubin and glutamate pyruvate transaminase. Morphology of liver tissue and levels of marker enzymes indicated that berberine offered protection against chemical carcinogenesis.

Effects of hyperthermic isolated limb perfusion with tumor necrosis factor-alpha and melphalan on pulmonary function assessments.

High doses of tumor necrosis factor-alpha (TNF) seem to be effective in the treatment of solid tumors in the extremities. By applying current intensive care technology, systemic administration of high doses of TNF levels might be feasible for the treatment of cancer in other localizations. To establish the early and late effects of high systemic TNF levels on the lungs, we determined lung function parameters in 12 patients before and after hyperthermic isolated limb perfusion (HILP) with TNF and melphalan. Because of leakage during perfusion, mean maximum systemic TNF levels of 60.0 ng/ml (range, 0.3-356 ng/ml) were obtained. Significant alterations in the vital capacity (VC), the capillary blood volume (Vc), the diffusing capacity of the alveolocapillary membrane (Dm), and the transfer capacity of the lungs for carbon monoxide per unit alveolar volume (KCO) were observed 1 week after HILP. Eight weeks after HILP, they returned to pretreatment value. Alterations in lung functions were not related to the maximum systemic TNF level. In conclusion, disturbances in pulmonary functions are observed in patients after HILP with TNF and melphalan. These disturbances, which are probably partly caused by high systemic TNF levels, are reversible and would not preclude administration of systemic TNF in high doses.

[O2 utilization during hyperthermic extremity perfusion with rhTNF alpha and melphalan]. / O2-Utilisation während und nach hyperthermer Extremitätenperfusion mit rhTNF alpha und Melphalan.

During isolated limb perfusion (ILP) severe metabolic impairment with a subsequent alteration in oxygen consumption can be observed. The mechanisms responsible for this may be extracorporeal circulation, hyperthermia, and application of cytostatic drugs and cytokines. Thirty-three patients underwent ILP with rhTNF alpha and melphalan for melanoma or soft-tissue sarcoma. Cardiopulmonary monitoring consisted of arterial and mixed venous blood-gas analysis and a Swan-Ganz catheter was inserted after induction of general anesthesia prior to any surgical intervention. Arterial (SaO2) and mixed venous (SvO2) oxygen saturation, serum lactate and end-expiratory CO2 concentration were determined peri- and postoperatively for 72 h. Oxygen supply and consumption rates were measured systemically (DO2I, VO2I) and in the extracorporeal circuit ('DO2I, 'VO2I). For statistical analysis we used the t-test. During extracorporal circulation an increase of DO2I and VO2I was observed. A slight increase of lactate values began during the wash-out phase. Immediately after reperfusion. DO2I, VO2I and lactate increased significantly with normalization until the 2nd postoperative day. SaO2 and SvO2 remained unchanged. A significant correlation between regional toxicity and the postoperative maximum of serum lactate values was found. The increase of DO2I and VO2I in the tissues during ILP and after reperfusion was achieved by a significant increase in cardiac output while the oxygen extraction rate was not altered. Elevation of lactate values after reperfusion and the increase in oxygen utilization might be due to oxygen depletion in the perfused limb. This could contribute to the development of lactacidosis or rhabdomyolysis. Therefore, to minimize toxicity it seems to be mandatory to measure adequate tissue oxygen supply during ILP.

Intracompartmental pressure during hyperthermic isolated limb perfusion for melanoma and sarcoma.

Side effects of isolated limb perfusion (ILP) include rhabdomyolysis, paresthesia, or nerve palsy. The increase in intracompartmental pressure during ILP is thought to be linked to neuro- and muscular toxicity, and fasciotomy is recommended for protection. In 24 patients, intracompartmental pressure was measured. A flexible 5 F probe was placed into the non-tumour-bearing compartment of the perfused limb. Interstitial fluid pressure was measured using a piezoresistant tip. Compartmental pressure values were continuously recorded during and after ILP. The drugs used were a combination of doxorubicin, cisplatinum and melphalan or rhTNF-alpha combined with melphalan. The median overall compartmental pressure prior to ILP was 13 mmHg (range: 11-21 mmHg); during the heat-up phase the median pressure rose to 28 mmHg. During therapeutic perfusion a further increase could be documented and the maximum pressure measured was 90 mmHg; the median of the pressure maxima of all patients was 34 mmHg. During wash-out, at the end of the perfusion, a clear reduction in compartment pressures could be observed and the median dropped to a value of 27 mmHg. In all patients a continuous decrease in compartmental pressure could be recorded, reaching the pre-ILP values by 48 h post-operatively. A dramatic increase in compartmental pressure during ILP can be observed by continuous monitoring. Because of our observation that during the wash-out phase elevated compartmental pressures return to normal, there is no general indication for a fasciotomy. However, for patients maintaining a peak compartmental pressure above a critical threshold of 35 to 40 mmHg fasciotomy may be indicated.

A three-dimensional thermal and electromagnetic model of whole limb heating with a MAPA.

Previous studies by the authors have shown that if properly implemented, the Pennes assumptions can be applied to quantify bioheat transfer during extremity heating. Given its relative numerical simplicity and its ability to predict temperatures in thermoregulated tissue, the Pennes model of bioheat transfer was utilized in a three-dimensional thermal model of limb heating. While the arterial blood temperature was assumed to be radially uniform within a cross section of the limb, axial gradients in the arterial and venous blood temperatures were computed with this three-dimensional model. A realistically shaped, three-dimensional finite element model of a tumor-bearing human lower leg was constructed and was "attached" mathematically to the whole body thermal model of man described in previous studies by the authors. The central as well as local thermoregulatory feedback control mechanisms which determine blood perfusion to the various tissues and rate of evaporation by sweating were input into the limb model. In addition, the temperature of the arterial blood which feeds into the most proximal section of the lower leg was computed by the whole body thermal model. The variations in the shape of the tissues which comprise the limb were obtained from computerized tomography scans. Axial variations in the energy deposition patterns along the length of the limb exposed to a miniannular phased array (MAPA) applicator were also input into this model of limb heating. Results indicate that proper positioning of the limb relative to the MAPA is a significant factor in determining the effectiveness of the treatment. A patient-specific hyperthermia protocol can be designed using this coupled electromagnetic and thermal model.

Effects of hyperthermia and/or hyperglycemia on pH and pO2 in well oxygenated xenotransplanted human sarcoma.

The heat-induced interdependent changes of tumor blood flow, pO2, and pH decisively influence the therapeutic effect of hyperthermia (HT). This fact has induced us to determine simultaneously the frequency distribution of local pO2 values and the intratumoral pH in a xenotransplanted human sarcoma cell line at a normal blood glucose level and under hyperglycemic conditions before, during, and after HT. Two groups, one of 10 and one of 9 congenitally athymic nude rats with a subcutaneously implanted S117 human sarcoma into the right hind paw (mean tumor volume 5.3 cm3) were treated with local waterbath HT (tumor temperature 43 degrees C, 1 hr) alone or in combination with i.p. glucose injections (6 g/kg, 2 hr before the onset of HT). Tumor oxygenation remained improved throughout HT. Tumor pH did not decrease during HT. Hyperglycemia alone elicited a decrease of intratumoral pH and pO2, probably mainly due to hemoconcentration. The additional warming of the tumors (43 degrees C) during hyperglycaemia did not further decrease pO2 and pH. Silver stained sections of the tumors showed only a few very small necrotic areas, even in tumors of volumes up to 8 cm3. Our results indicate a well oxygenated tumor. In contrast to most tumors studied so far, hyperthermia in this tumor induces not only an initial increase of oxygenation but a lasting elevation of mean tumor pO2 for the duration of HT (up to 60 min).

Local RF capacitive hyperthermia: thermal profiles and tumour response.

At the Cancer Institute we are using RF capacitive hyperthermia as an adjuvant to radiotherapy and/or chemotherapy in the local control of soft tissue sarcomas. We have studied the influence of bolus conductivity, electrode and phantom sizes on the rate of heating of agar phantoms. We have varied the bolus conductivity by varying the saline concentration in the bolus bags from zero to 2.0 per cent, during heating. We found that the rate of heating of phantoms increases and that of the bolus decreases with the increase in the saline concentration of bolus up to 1 per cent, irrespective of phantom and electrode sizes. However, for a given size of electrodes the rate of heating decreased with the increase in the phantom size. When the diameter and height of the phantom were equal to the diameters of electrodes the rate of heating of the phantom was nearly uniform. However, when the diameter of the phantom was larger than that of electrodes the rate of heating in the radial axis decreased with the increase in the radial distance. On the basis of this data we suggest the use of electrodes larger in size by 1.0-3.0 cm than the size of the tumour, where the size of the anatomical site to be heated is larger than the electrode size to be used. Phantom and clinical data have indicated that the presence of bone in the field of heating can lead to hot spots. Preliminary clinical results have shown that the response of sarcomas to thermo-chemo-radiotherapy was superior to that of either thermo-radiotherapy or radiotherapy alone.

pH distribution in human tumors.

The effectiveness of hyperthermia in tumor therapy may depend on a lower extracellular pH of tumor compared to that of normal tissue. A technique for measuring extracellular pH in human tumors has been devised to test the usefulness of this parameter as prognostic indicator of tumor hyperthermia response. In a preliminary study 50 of 53 pH readings from 14 human tumors (both heated and unheated) were below normal physiological pH. Tumor pH values ranged between 5.55-7.69 (average for unheated tumors 6.81 +/- 0.09, SEM, only one determination was above 7.40). Although there was considerable heterogeneity of pH within tumors, the accuracy and drift of the 21 gauge needle electrode were not a problem. Fifteen minutes were required for pH stabilization after insertion of an 18 gauge open-ended catheter, and less than 5 min for equilibration after electrode insertion into the catheter. A saline wheal was used for anesthesia to preclude modification of pH by anesthetics. Central portions of tumors were no more acidic than peripheral regions, but large tumors tended to be more acidic than small tumors. The pH of several tumors of various sizes and histologies was also determined immediately before subsequent treatment sessions. These measurements were made by reinsertion of catheters in approximately the same locations at each session. The trend appeared to be that pH increased with the number of treatment sessions. Measurements of pH were made in four patients immediately prior to and at the termination of a heating session (same locations since catheter remained in place during heating sessions). Three of the four tumors showed increased pH readings of 0.25-0.54 units during heating. However, none of the four tumors achieved temperatures exceeding 42 degrees C. The pH measurement technique developed provides a safe and relatively easy method for determining extracellular pH in human tumors. There appears to be a correlation of pH values with tumor size, treatment session, and possibly blood flow.