P11.50 The dielectric properties of brain tumor tissue

BACKGROUND

Recently, tumor treating fields (TTFields) were established for the treatment of newly diagnosed GBM. One of the most crucial parameters defining the treatment efficacy of TTFields is the electric field intensity. The dielectric properties of the normal intracranial compartments are well established, allowing the prediction of the electric field distribution. In contrast, there is no data available about the dielectric properties of brain tumor tissue. In this study we determined the dielectric properties of brain tumors by analyzing resected tissue following a fast acquisition protocol. To account for the intratumoral heterogeneity, different regions of the tumor were analyzed separately.

MATERIAL AND METHODS

A cohort of 84 patients with tumors of different histology and malignancy grade have been recruited (meningioma: n=26; brain metastases n=18; low grade glioma n=6; glioblastoma n=34). Tissue probes were acquired whenever possible from the vital tumor area, and perinecrotic compartment identified intraoperatively using neuronavigation, intraoperative ultrasound and fluorescence guidance. After acquisition, the tissue was measured immediately to avoid artifacts induced by temperature change, differences of fluid composition as well as post resection ischemia. A fragment was dissected from each tissue sample and was placed into a cylindrical cell with a known diameter. Two parallel electrodes were placed on both sides of the sample and the thickness of the tissue was measured using a micrometer. The impedance was recorded at frequencies 20Hz-1MHz using a software specifically developed for this study, which controls the LCR meter (Keysight Technologies, Santa Rosa, USA). The measured impedance was translated into dielectric properties of the sample (conductivity and relative permittivity) based on the parallel plate model, the recorded complex impedance and the geometry of the samples. Each tissue probe was fixed, H&E stained and histologically analyzed.

RESULTS

We found significant differences between the conductivity of different types of tumors with meningiomas showing the lowest conductivity (mean conductivity [S/m]: 0.193; range: 0.327 - 0.113) and GBM tissue exhibiting the highest conductivity values (mean conductivity [S/m]: 0.402; range: 0.893 - 0.157). Consistently, the perinecrotic areas of tumors displayed lower conductivity values compared to the solid tumor compartments. Also, we found a significant intratumoral heterogeneity in tumors of one specific histological diagnosis.

CONCLUSION

The dielectric properties of intracranial tumors appear to be depending on histological class and malignancy grade and show significant intratumoral heterogeneity. These results may allow a more precise modelling of electric field intensity distribution within the tumor.

Lebensqualit�t und Patientenzufriedenheit nach Kataraktchirurgie

BACKGROUND

Assessment of patient satisfaction and quality of life becomes increasingly important for the overall evaluation of therapy regimes. However, it is not certain whether standard quality of life questionnaires suffice to assess immediate changes in patient conditions such as induced by cataract surgery.

METHODS

The increase in visual acuity was observed in 152 cataract patients as an objective efficacy parameter. In addition, subjective patient satisfaction and quality of life was obtained from these patients by means of a cataract-specific questionnaire 1 day before and 4 weeks after surgery. The questionnaire concentrates on the patients' overall flexibility and mobility, their estimation of medical and nursing care, changes in ophthalmological conditions and on complications after surgery.

RESULTS

With an internal consistency of 82% the instrument can be regarded as moderately reliable but self-reported quality of life before surgery was found to be remarkably biased. None of the above quality of life determinants showed a clinically relevant correlation with the objective increase in visual acuity (absolute correlations <20%). Significant impact factors for overall quality of life satisfaction were the patients' overall flexibility ( p=0.049) and their estimation of medical and nursing care ( p=0.027).

CONCLUSIONS

Standard quality of life determinants provide independent subjective information in addition to the increase in visual acuity as an objective measure of clinical outcome. Overall assessment of patient satisfaction cannot be regarded as sufficient for the subjective evaluation of cataract surgery, since its estimation primarily depends on the patients' appreciation of medical and nursing care. An appropriately extensive means of quality of life assessment seems necessary and post-surgical data seems sufficient for the estimation of subjective therapy outcome measures in cataract patients.

[Genotoxic effect of the insecticides pentachlorophenol and lindane on human nasal mucosal epithelium]

BACKGROUND AND OBJECTIVE

In numerous experimental and epidemiologic studies Pentachlorphenol (PCP) and Hexachlorcyclohexan (Lindane) have been shown to be of potential carcinogenic risk for human epithelial cells. In the past, these two substances have been used for both, military and non-military purposes, e.g. for impregnation of textiles and uniforms. In this study we investigated the genotoxic effect of PCP and Lindane on human mucosal tissue from the middle and lower nasal turbinate.

METHODS

In biopsy samples obtained from nasal epithelia during surgery cell vitality was evaluated by trypan-blue-staining. The specimens were incubated for 60 minutes with PCP (0.3; 0.75 und 1.2 mumol/l) and Lindane (0.5; 0.75; and 1.0 mumol/ml). The induction of DNA-damage (single-strand-breaks and double-strand-breaks) caused by PCP and Lindane was measured using single-cell microgel electrophoresis. Evaluation was performed by fluorescence microscopy.

RESULTS

Especially in mucosa cells from the middle turbinate severe DNA-damages were recognized after exposition to PCP and Lindane proposing a strong genotoxic effect. In cells from the lower turbinate DNA-changes caused by PCP and Lindane were significantly lower. However a considerable genotoxic effect was also present.

CONCLUSION

This study shows for the first time that there are clear facts indicating mutagenic effects of PCP and Lindane on nasal epithelia. Furthermore, this is the first study showing different susceptibility of two anatomic subsites in the nose for different pesticides. Concerning the biological plausibility, this study offers important arguments for evaluating the role of PCP and Lindane in the induction of upper aerodigestive tract cancer.