Biomedical subjects

M Bamberg

Publications and source records attributed to M Bamberg.

242 records · Page 14Linked to original sources

PubMedDate not supplied

An on-line phase measurement system for quality assurance of the BSD 2000. Part II: results of the phase measurement system.

Phase constancy and accuracy are significant for regional hyperthermia with phased array radiofrequency hyperthermia systems. They are both necessary for a precise target steering in therapy. For the BSD 2000 system (BSD Medical Corp. Salt Lake City, Utah, USA), the phase values of all channels are checked with a self-developed automatic on-line phase measurement system. On different days the phases are measured under identical conditions, where the output paths are cut off with 50 ohm dummy loads to suppress the influence of the radiation conditions of the antennae on the measurement values. The results show how the phase values of the four channels change in the first 30 min and from day to day. During this time interval after the start the phases drop down by up to 15 degrees. For the time later changes are very slight and the differences from day to day are negligible. The phase shift that occurs in the first 30 min is as high as a change of the target point by 1 cm. Earlier switching on of the amplifiers prevents this shift occurring during the treatment. The measurement system provides a good tool for determination of phase accuracy and is easy to realize.

Humans↗

PubMedDate not supplied

Thermoradiotherapy for locally recurrent breast cancer with skin involvement.

PURPOSE: This retrospective analysis investigated the effectiveness and side-effects of combined hyperthermia and radiation therapy in locally recurrent breast cancer after primary modified radical mastectomy. The aim of the thermoradiotherapy was to reduce the substantial risk of symptomatic chest wall disease. MATERIALS AND METHODS: Between May 1995-August 1998, 39 extensively pre-treated women with progressive locoregional chest wall tumours were treated with local radiofrequency hyperthermia, given twice a week immediately before radiotherapy. Sixty-two per cent of the patients had received previous radiotherapy, with a median dose of 50 Gy, 64% had received chemotherapy, 36% hormonal therapy, and 13% local therapy with miltefosin, respectively. Nine patients were treated for microscopic residual disease after local tumour excision (R1-resection) and 30 patients for gross macroscopic nodular recurrences. Twenty-seven patients had two adjacent hyperthermia fields at the ipsilateral chest wall to cover the whole irradiation area. Each field received a median of seven local hyperthermia sessions (range 2-12, average 5.6 sessions) just before radiation therapy, with a median dose of 60 Gy (range 30-68 Gy). The monitored maximum(average) and average(average) epicutaneous temperatures were 42.1 degrees C and 41.0 degrees C, respectively. Maximum(average) and average(average) intratumoural temperatures of 43.0 degrees C and 41.1 degrees C, respectively, were achieved in nine chest wall recurrences with intratumoural temperature probes. Concurrent hormonal therapy was administered in 48%, and concurrent chemotherapy in 10% of patients. RESULTS: Median overall survival time was 28 months (Kaplan Meier), with 71% and 54% of patients living 1 and 2 years after thermoradiotherapy. The median time to local failure has not been reached, local tumour control after 2 years being 53%. Actuarial 1 and 2 year local tumour controls for microscopic residual disease were 89%, and for macroscopic nodular recurrences 71% and 46%, respectively (p = 0.09). Actuarial 1 and 2 year local tumour controls after treatment with a total dose of less than 60 Gy were 51% and 38%, respectively, and, after a total dose greater than 60 Gy, 84% and 60% (p = 0.01), respectively. Actuarial 1 year local tumour control was 92% after complete tumour remission, versus 57% after partial remission (p = 0.002). Three of the 39 patients died of cancer en cuirasse, 13 patients due to distant metastases. Acute thermoradiotherapy related erythema, dry desquamation and moist desquamation were seen in 28.2%, 30.7%, and 30.7% of patients, respectively. Soft tissue necrosis occurred in two patients with previous post-operative delayed wound healing, and in one patient above a silicon implant. CONCLUSION: This study showed that, in extensively pre-treated patients with locally recurrent breast cancer, local tumour control after thermoradiotherapy depended on tumour resectability, response of macroscopic tumour to thermoradiotherapy, and total irradiation dose.

Adult↗

PubMedDate not supplied

Appendicitis during locoregional thermoradiotherapy of advanced or recurrent rectal and cervical cancer, a report of two cases.

INTRODUCTION: Local tumour control after irradiation alone for advanced, inoperable carcinomas of the bladder and rectum or inoperable recurrent cervical carcinoma is usually disappointing. Both preclinical and clinical studies reported improvements by adding hyperthermia to radiotherapy. Reports for phase II/III trials do not indicate any enhanced side effects. However, two cases of acute suppurating appendicitis were observed in a series of patients treated with deep regional hyperthermia. MATERIALS, METHODS AND RESULTS: Eighty patients with advanced, inoperable, or recurrent rectal or recurrent cervical tumours were treated with deep regional hyperthermia (313 sessions) in addition to radiotherapy between September 1995 and October 1998. The treatment for two of these patients (2.5%) had to be discontinued after the fourth/second hyperthermia treatments at 19.8/10.8 Gy total dose, respectively, for symptoms of pain in the right pelvis and elevated rectal temperature. Both patients underwent laparotomy and were found to have suppurative appendicitis. In addition to the retrocoecal location in both patients, evidence of preexisting chronic appendicitis, and appendiceal faecalith were observed in each patient. CONCLUSION: The development of acute appendicitis in 2.5% of patients during a course of deep regional thermoradiotherapy for pelvic tumour is much higher than the expected incidence of appendicitis in the general population (< 1/1000) (Korner et al. 1997). An enhanced risk of suppurative appendicitis in patients undergoing pelvic thermoradiotherapy cannot be excluded, especially in retrocoecal located appendices with obstructed appendix lumen from preexisting chronic appendicitis or faecalith.

Appendicitis↗

PubMedDate not supplied

Future strategies in external radiation therapy of renal cell carcinoma.

The advantage of external radiation therapy in renal cell carcinoma is controversial. High complication rates reported in previous trials of postoperative radiation therapy can now be avoided by using contemporary modern treatment techniques. Based on both prospective and retrospective data the following indications for adjuvant radiation therapy should be considered and tested in phase III trials: a) unresectable non-metastatic tumours (preoperative irradiation), b) incomplete resection with gross or macroscopically positive margins, c) locally advanced tumour with perinephric fat extension or adrenal invasion.

Carcinoma, Renal Cell↗

PubMedDate not supplied

Radiosurgery for the treatment of brain metastases in renal cell carcinoma.

BACKGROUND: In the treatment of brain metastases using a stereotactically modified linear accelerator it could be shown that a single dose between 15 and 25 Gy leads to partial or complete remission of so-called radioresistant metastases from melanoma and hypernephroma. Radiosurgery of brain metastases then started in centers all over the world, however, experiences with brain metastases of renal cell carcinoma are yet limited. The aim of this analysis is therefore to present the treatment results of radiosurgery of brain metastases. Furthermore, in this paper prognostic subgroups shall be defined, in order to establish guidelines for an optimal therapy strategy. MATERIALS AND METHODS: Radiosurgery means stereotactically guided high-precision irradiation methods by extremely focussing ionizing radiation within the target volume as a single dose application. The characteristic steep dose decrease allows the selective destruction of small intracranial lesions, while the surrounding brain tissue is optimally protected. Two methods, Gamma Knife and stereotactic modified linear accelerator are clinically available. RESULTS: In larger studies from different groups all over the world, local tumor control rates from 85% to 95%, recurrence rates from 6% to 15% and side effects between 3% and 15% have been attained, independent of the system used. Prognostic factors, like volume of metastases < 10 ml, applied dose > 18 Gy, one or two metastases, absence of extracranial metastases, good patient performance with a Karnofsky score > 70%, primary treatment and more than one year between primary diagnosis and brain metastases showed a trend toward improved survival. Depending on the prognostic factors the median survival after radiosurgery ranged from 6 to 12 months. Retrospective comparison of radiosurgery and surgical series suggest that both modalities attain similar results. The dose can be applied with an accuracy of 0.3 mm. DISCUSSION: Based on these experiences, brain metastases can be treated by radiosurgery, primarily in patients with one or two metastases or in combination with whole brain irradiation as a boost in patients with more than two metastases. Furthermore with radiosurgery a new treatment modality exists to re-irradiate patients who have been failed after surgery or whole brain irradiation.

Bone Neoplasms↗

PubMedDate not supplied

Irradiation induced clonogenic cell death of human malignant glioma cells does not require CD95/CD95L interactions.

BACKGROUND: Radiotherapy is the single most effective therapy for malignant gliomas. Targeting the CD95 apoptotic pathway is a promising experimental approach to these neoplasms. Here, we asked whether irradiation modulates CD95-mediated apoptosis of human malignant glioma cells in vitro. MATERIALS AND METHODS: LN-18, LN-229 and T98G human malignant glioma cell lines were irradiated with dosages from 0-8 Gy and treated with CD95L (CD95 ligand). CD95 expression was assessed by flow cytometry. Caspase activity was determined by DEVD cleavage. Cytotoxic effects were assessed by crystal violet staining of cells in a 96-well plate assay. Clonogenic cell death was determined by a standard colony forming assay. RESULTS: We find that (i) CD95L-induced apoptosis, but not irradiation-induced clonogenic cell death, involves caspase 3 activation and is blocked by the viral caspase inhibitor, crm-A. (ii) Irradiation does not modulate CD95 expression either in p53 wild-type or in p53 mutant glioma cell lines, and does not enhance CD95L-evoked caspase 3 activity or CD95L-induced clonogenic cell death. CONCLUSIONS: We conclude that endogenous CD95/CD95L interactions are not involved in radiation-induced clonogenic cell death and that the killing cascades of CD95L and irradiation are independent in human malignant glioma cells.

Apoptosis↗

PubMedDate not supplied

Soluble levels of CD-95, CD 95-L and various cytokines after exposing human leukocytes to ionizing radiation.

BACKGROUND: Local radiotherapy induces systemic effects and influences the immune system. Some of these effects can hardly be explained by direct cellular reactions, but might be triggered by humoral factors. MATERIALS AND METHODS: In seminoma patients we measured the influence of radiotherapy on various lymphocyte subsets by FACS-analysis. We analysed the release of cytokines, CD95 (Apo-1/Fas) and CD 95-L (Fas-Ligand) of human blood cells after exposure to ionizing radiation in vitro and in vivo by ELISA-technique. RESULTS: Although radiation leads to a differential and sustained reduction of all lymphocytes subsets in vivo no increase of cytokine levels, or of levels of CD95 or CD 95-L could be detected by ELISA in vivo or in vitro. On the contrary mitogen-induced cytokine production in vitro was inhibited by radiation. CONCLUSIONS: Local radiation induced a significant systemic decrease of all lymphocyte subsets, but neither a systemic release of cell death mediators like CD95 or various cytokines, nor a release in the extracellular space in vitro were detectable.

Adult↗

PubMedDate not supplied

MEK1 and Erk1/2 kinases as targets for the modulation of radiation responses.

BACKGROUND: The activation of mitogenic cascades via Ras, c-Raf-1, MEK-1, Erk1/2 is a hall- mark of oncogenic transformation. The cascade is also anti-apoptotic by modulation of Bcl-2, Bcl-xL and BAD function. The impact of MEK-1 on radiation resistance and the role of drugs targeting MEK-1 for the modulation of resistance is unclear. MATERIALS AND METHODS: Activation of MEK-1 in four carcinoma cell lines was analyzed using Erk1/2 phosphospecific antibodies. MEK-1 was blocked by PD98059 (2-amino-3methoxyflavin) and influence on radiation responses was determined by apoptotic morphology, caspase-3 activation and colony formation assays. RESULTS: MEK-1 kinase was constitutively active and inhibitable by PD98059. The low radiation induced apoptosis rate was not increased by MEK inhibition. PD98059 did not influence cell growth and radiation induced clonogenic cell death. CONCLUSION: Since PD98059 did not alter radiation responses despite blocking MEK-1 kinase, MEK-1 and Erk1/2 are not involved in radiation resistance. Thus PD98059 has no potential in the modulation of radiation responses.

Apoptosis↗