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Biomedical subjects

J G Wolbers

Publications and source records attributed to J G Wolbers.

At least 19 recordsLinked to original sources
PubMed2001

['Benign' meningioma].

Meningioma was diagnosed in four women, aged 40, 24, 41 and almost 75 years, respectively. The first of these patients was treated with surgery, the second and third patients underwent surgery followed by conventional radiotherapy because of a tumour residue or dural tail, and the last patient was treated with stereotactic radiosurgery. They recovered well and were followed by means of regular outpatient check-ups. Twenty percent of all primary brain tumours are meningiomas, over 90% of which are benign. Nevertheless, a large hospital-based population study showed a 5-year survival rate of only 70%. Microsurgery is usually the treatment of first choice. However, in about 25% of cases, excision is incomplete and tumour growth almost always continues. Further surgery influences prognosis unfavourably. New sophisticated radiation techniques help to control tumour progression in about 80-90% of cases. This success, however, may be associated with new cranial nerve deficits or panhypopituitarism. Prospective, comparative studies are not available.

Adult↗
PubMed2001

[Meningiomas: prognostic relevance of histopathologic and genetic markers].

The majority of meningiomas are histologically benign tumours. Location and invasion of tumour tissue in adjacent structures may hamper radical resections and give rise to recurrences. The rise in human life expectancy has prolonged the postoperative period and thus the risk of tumour recurrence has increased markedly. Infiltration in brain tissue and mitotic activity are important histologic features which negatively influence the disease-free duration of the postoperative period. Molecular studies of relevant genetic defects involved in meningioma are currently underway, but as yet these are of little clinical relevance.

Biomarkers, Tumor↗
PubMed2000

[Stereotaxic irradiation of vestibular schwannoma (acoustic neuroma)].

A vestibular schwannoma (acoustic neurinoma) is a benign tumour localized in the cerebellopontine angle; it can give rise to cranial nerve symptoms. In recent years stereotactic irradiation has become an alternative to radical surgery. Stereotactic irradiation is administered with a gamma knife unit or with an adapted linear accelerator, as a single fraction (radiosurgery) or fractionated (stereotactic radiation therapy). Stereotactic irradiation gives local control rates of over 90%. Post treatment hearing preservation rate is over 60% and treatment related toxicity is low. Comparable treatment results are also found in the Netherlands at the VU-Ziekenhuis in Amsterdam.

Computer Simulation↗
PubMed2000

Fractionated stereotactic radiation therapy and single high-dose radiosurgery for acoustic neuroma: early results of a prospective clinical study.

PURPOSE: To prospectively assess the local control and toxicity rate in acoustic neuroma patients treated with linear accelerator-based radiosurgery and fractionated stereotactic radiation therapy. METHODS AND MATERIALS: We evaluated 37 consecutive patients treated with stereotactic radiation therapy for acoustic neuroma. All patients had progressive tumors, progressive symptoms, or both. Mean tumor diameter was 2.3 cm (range 0.8-3.3) on magnetic resonance (MR) scan. Dentate patients were given a dose of 5x4 Gy or 5x5 Gy and edentate patients were given a dose of 1x10 Gy or 1x12.50 Gy prescribed to the 80% isodose. All patients were treated with a single isocenter. RESULTS: With a mean follow-up period of 25 months (range 12-61), the actuarial local control rate at 5 years was 91% (only 1 patient failed). The actuarial rate of hearing preservation at 5 years was 66% in previously-hearing patients. The actuarial rate of freedom from trigeminal nerve toxicity was 97% at 5 years. No patient developed facial nerve toxicity or other complications. CONCLUSION: In this unselected series, fractionated stereotactic radiation therapy and linear accelerator-based radiosurgery give excellent local control in acoustic neuroma. It combines a high rate of preservation of hearing with a very low rate of other toxicity, although follow-up is relatively short.

Adult↗
PubMed2000

Additive cytotoxic effect of cisplatin and X-irradiation on human glioma cell cultures derived from biopsy-tissue.

PURPOSE: Investigation of the in vitro cytotoxic effect of X-rays, either alone or combined with cisplatin on early passage cell cultures derived from human glioblastoma multiforme biopsy tissue. MATERIALS AND METHODS: Fresh tumour specimens from four patients were processed to cell cultures. The U373 glioma cell line was used as a reference. Early passage cell cultures were X-irradiated (0-8 Gy) either alone or in combination with cisplatin (0.5-1 microgram/ml). Cell survival was determined by either clonogenic assay or the colorimetric MTT assay. Survival curves were generated and mathematically analysed using the linear quadratic model, to obtain the radiosensitivity parameters alpha, beta, and SF2, i.e., the Surviving Fraction after 2 Gy. RESULTS: Two patient-derived glioma cell cultures and the U373 cell line showed rather high SF2 values of 0.61-0.72 in the clonogenic assay, indicating relative high radiation resistance. Cisplatin alone (1 microgram/ml) reduced cell survival by 10-30% (n = 4). When combined with irradiation, a clear additive cytotoxic effect of cisplatin was demonstrated by the unaltered value of the alpha-parameter for reproductive cell death. CONCLUSION: Cisplatin exerted an additive rather than radiosensitising cytotoxic effect in uncharacterised patient derived glioma cell cultures.

Adult↗
PubMed2000

Bleeding risk of cerebrovascular malformations in hereditary hemorrhagic telangiectasia.

OBJECT: Hereditary hemorrhagic telangiectasia (HHT) is a rare autosomal-dominant vascular dysplasia with a high prevalence of cerebrovascular malformations (CVMs), mostly manifested as arteriovenous malformations (AVMs). The natural history and bleeding risk of these CVMs is unknown. The authors investigated the risk of bleeding in conjunction with clinical and radiological features in patients with HHT and proven CVMs. METHODS: Intravenous digital subtraction (DS) angiography was used to screen 196 patients with HHT for the presence of CVMs. Patients with abnormal results on DS angiography were asked to undergo a conventional cerebral angiographic study. All patients with a proven CVM were assessed by a neurologist. The bleeding risk was retrospectively and prospectively calculated for patients with AVMs only, as well as for the whole cohort of patients with CVMs. Twenty-four patients (12.2%; 16 female and eight male), aged 14 to 66 years (mean 35.4 years) with one or more CVMs were identified. Fifteen patients (62.5%) had a CVM and a pulmonary AVM. Eleven patients (45.8%) exhibited no neurological signs of their CVM; six (25%) had headache or migraine; four (16.7%) had seizures; and three (12.5%) had an intracranial hemorrhage. Twenty-two patients had at least one AVM (with a total of 28 AVMs), whereas two patients only had telangiectases. Twenty-seven AVMs were small (96%), 36% were located in eloquent areas of the brain, and 82% had superficial venous drainage. One third of the patients had multiple CVMs. The bleeding risk for patients with at least one AVM ranged from 0.41 to 0.72% per year, and for the whole cohort the range was 0.38 to 0.69% per year. Calculation of the bleeding risk as determined by lesion-years ranged from 0.36 to 0.56% per year for patients with AVMs and from 0.27 to 0.46% per year for all patients with CVMs. CONCLUSIONS: Patients with HHT have a high risk of harboring a CVM, especially in the presence of a pulmonary AVM. These CVMs are mostly low-grade AVMs (Spetzler-Martin Grade I or II), are frequently multiple, and have a lower risk of bleeding than that associated with sporadic AVMs. Female patients are more often affected than male patients. The inherent low sensitivity of DS angiography screening for CVMs may yield false negative results.

Adolescent↗
PubMed1999

[Stereotactic radiosurgery with adjusted linear accelerator for cerebral arteriovenous malformations: preliminary results in the Netherlands].

OBJECTIVE: To assess the effects of stereotactic radiosurgery of a cerebral arteriovenous malformation (AVM). DESIGN: Prospective. METHOD: In November 1991-December 1995 linear acceleration radiosurgery was performed on 29 patients for their 30 cerebral AVMs in the University Hospital Vrije Universiteit, Amsterdam, the Netherlands. There were 15 females and 14 males with a mean age of 37.1 years (range: 13-58). Generally one isocentre was used and 15 Gy was given to the margins of the AVM at the 80% isodose. The mean target volume was 2.4 ml (range; 0.5-8.2). After 6 months, one year and thereafter every year, neurological and MRI-controls took place, in the outpatient ward. Angiography was performed after an average of 35 months (range: 24-70) to check if the AVM had obliterated. RESULTS: Angiographic post-treatment results were available in 27 patients and MRI information in one. Angiographic obliteration occurred in 20 patients (71%). No permanent radiation-induced neurological deficit was seen, nor did any hemorrhage occur during the interval between irradiation and obliteration.

Adolescent↗
PubMed1999

Organisation and management of the first clinical trial of BNCT in Europe (EORTC protocol 11961).EORTC BNCT study group.

Boron Neutron Capture Therapy is based on the ability of the isotope 10B to capture thermal neutrons and to disintegrate instantaneously producing high LET particles. The only neutron beam available in Europe for such a treatment is based at the European High Flux Reactor HFR at Petten (The Netherlands). The European Commission, owners of the reactor, decided that the potential benefit of the facility should be opened to all European citizens and therefore insisted on a multinational approach to perform the first clinical trial in Europe on BNCT. This precondition had to be respected as well as the national laws and regulations. Together with the Dutch authorities actions were undertaken to overcome the obvious legal problems. Furthermore, the clinical trial at Petten takes place in a nuclear research reactor, which apart from being conducted in a non-hospital environment, is per se known to be dangerous. It was therefore of the utmost importance that special attention is given to safety, beyond normal rules, and to the training of staff. In itself, the trial is an unusual Phase I study, introducing a new drug with a new irradiation modality, with really an unknown dose-effect relationship. This trial must follow optimal procedures, which underscore the quality and qualified manner of performance.

Boron Neutron Capture Therapy↗
PubMed1998

Damage to tumour and brain by interstitial photodynamic therapy in the 9L rat tumour model comparing intravenous and intratumoral administration of the photosensitiser.

In the 9L rat brain tumour model the damage to tumour and normal brain by photodynamic therapy after intratumoural photosensitizer administration (intratumoural PDT) was studied. Twenty four rats received an intratumoural injection of 4 or 40 mm3 haematoporphyrin derivative (HpD, 5 mg ml-1), followed by interstitial irradiation with 20 Joule (J) (630 nm) 5 h later. For comparison, seven rats were treated with 20 Joule 24 h after an intravenous injection of 10 mg kg-1 HpD (intravenous PDT). With the chosen PDT parameters there was no important difference between the damaged areas produced by intratumoural PDT or intravenous PDT. No selective tumour kill was observed. Even though normal brain tissue was heavily damaged, vital tumour parts were still present. Intravenous PDT caused extensive diffuse damage to small blood vessels in tumour and surrounding normal brain. Intratumoural PDT was characterised by an infiltration of polymorphonuclear cells into damaged tissue, dilatation of larger blood vessels and gross haemorrhage. These results suggest an immediate vascular shutdown in the intravenous approach, while in the intratumoural approach the vasculature remained patent initially. Because of the severe side effects observed, the use of HpD seems not advisable for intratumoural PDT of brain tumours.

Animals↗
PubMed1998

5-Aminolevulinic acid induced endogenous porphyrin fluorescence in 9L and C6 brain tumours and in the normal rat brain.

A new approach in photodynamic therapy is the use of endogenous porphyrins for sensitisation of tumours to light. The induction of endogenous porphyrins after intravenous injection of 5-aminolevulinic acid (ALA, 200 mg kg-1) was studied in 23 rats, bearing intracranial 9L or C6 tumours. After 0, 2, 4, 6, 8, and 22 hours the rats were sacrificed and the fluorescence distribution of endogenous porphyrins was studied in brain tissue sections with a standard fluorescence microscope and a confocal laser scanning microscope. The role of blood-brain barrier disruption on porphyrin production was studied in 2 rats with a cryo-lesion of the cortex. Additionally, 9L and C6 tumour cell cultures were incubated with ALA for 8 hours in vitro. Fluorescence was measured with a fluorescence spectrophotometer in cell cultures and in the brain sections. Porphyrins were detected in vitro in the tumour cells from 2 hours onwards and ex vivo in the tumour sections mainly from 2 to 8 hours, by 22 hours porphyrin fluorescence had almost disappeared. The contralateral brain showed low fluorescence levels between 2 and 6 hours after ALA administration. At the site of the cryo-lesions low fluorescence was measured 6 hours after ALA administration. The 9L tumours fluoresced homogeneously, with a sharp demarcation towards normal brain tissue. Fluorescence in the C6 tumours was patchy, with a poorly fluorescing edge. In both tumour models fluorescence was also detected in brain surrounding the tumour and sometimes in contralateral white matter and ventricle ependyma and pia mater. The slight increase of porphyrin fluorescence in the normal brain of tumour bearing rats, compared to the absence of this in rats without a tumour, was attributed to transport by bulk flow of porphyrins made in the tumours, and possibly also of circulating porphyrins or ALA leaking from the tumour vessels.

Aminolevulinic Acid↗
PubMed1998

Thallium-201 SPECT as response parameter for PCV chemotherapy in recurrent glioma.

Combination chemotherapy with procarbazine, CCNU and vincristine (PCV) may be effective in patients with recurrent glioma. Response monitoring is mandatory, but radiological response evaluation is often difficult. We evaluated Thallium-201 (201Tl) SPECT as a response parameter in ten patients treated with intensive PCV chemotherapy for recurrent glioma. 201Tl-SPECT studies showed early changes (decreasing volume and intensity) in nine patients and these changes were more pronounced than radiological findings. 201Tl-SPECT results after completion of chemotherapy seemed to correlate with clininal findings during follow up. We conclude that 201Tl-SPECT may contribute to the assessment of response in patients treated with PCV chemotherapy for recurrent glioma.

Adult↗