Search PubMed⌕ Search

Biomedical subjects

F W Kreth

Publications and source records attributed to F W Kreth.

At least 37 records · Page 2Linked to original sources
PubMed1999

Surgery and radiotherapy compared with gamma knife radiosurgery in the treatment of solitary cerebral metastases of small diameter.

OBJECT: The aim of this retrospective study was to compare treatment results of surgery plus whole-brain radiation therapy (WBRT) with gamma knife radiosurgery alone as the primary treatment for solitary cerebral metastases suitable for radiosurgical treatment. METHODS: Patients who had a single circumscribed tumor that was 3.5 cm or smaller in diameter were included. Treatment results were compared between microsurgery plus WBRT (52 patients, median tumor dose 50 Gy) and radiosurgery alone (56 patients, median prescribed tumor dose 22 Gy). In case of local/distant tumor recurrence in the radiosurgery group, additional radiosurgical treatment was administered in patients with stable systemic disease. Survival time was analyzed using the Kaplan-Meier method, and prognostic factors were obtained from the Cox model. The patient groups did not differ in terms of age, gender, pretreatment Karnofsky Performance Scale (KPS) score, duration of symptoms, tumor location, histological findings, status of the primary tumor, time to metastasis, and cause of death. Patients who suffered from larger lesions underwent surgery (p < 0.01). The 1-year survival rate (median survival) was 53% (68 weeks) in the surgical group and 43% (35 weeks) in the radiosurgical group (p = 0.19). The 1-year local tumor control rates after surgery and radiosurgery were 75% and 83%, respectively (p = 0.49), and the 1-year neurological death rates in these groups were 37% and 39% (p = 0.8). Shorter overall survival time in the radiosurgery group was related to higher systemic death rates. A pretreatment KPS score of less than 70 was a predictor of unfavorable survival. Perioperative morbidity and mortality rates were 7.7% and 1.6% in the resection group, and 8.9% and 1.2% in the radiosurgery group, respectively. Four patients presented with transient radiogenic complications after radiosurgery. CONCLUSIONS: Radiosurgery alone can result in local tumor control rates as good as those for surgery plus WBRT in selected patients. Radiosurgery should not be routinely combined with radiotherapy.

Adolescent↗
PubMed1997

Supratentorial World Health Organization Grade 2 astrocytomas and oligoastrocytomas. A new pattern of prognostic factors.

BACKGROUND: Prognostic factors for adult patients with supratentorial World Health Organization (WHO) Grade 2 astrocytomas and poorly defined. METHODS: The prognostic importance of pretreatment patient- and tumor-related factors was analyzed retrospectively in 197 adult patients with supratentorial astrocytomas (n = 153) or oligoastrocytomas (n = 44) using the multivariate Cox proportional hazards model. Endpoints were death and date of malignant transformation. All patients were treated similarly between 1979 and 1992 with iodine-125 implants as the primary treatment. RESULTS: A new prognostic pattern was detected. Unfavorable prognostic factors with regard to survival were 1) a tumor volume > or = 20 mL; 2) a performance status < or = 80; and 3) age > or = 40 years for the female subpopulation. Midline shift (another important tumor-related factor after univariate analysis) was highly correlated with tumor volume and therefore not included in the multivariate model. Risk factors of malignant transformation were 1) a tumor volume > or = 20 mL; 2) an enhancement in the computed tomography scan; and 3) age > or = 40 years for the female subpopulation. Prognostic factors created subsets of patients with 5-year survival rates ranging from as low as 5% to as high as 79%. CONCLUSIONS: Any treatment decision or evaluation of treatment efficacy should take into account the strong influence of both patient- and tumor-related factors. Any further study design should consider the detected interaction between gender and age and the importance of tumor volume.

Adult↗
PubMed1997

The risk of interstitial radiotherapy of low-grade gliomas.

BACKGROUND AND PURPOSE: The risk of side effects of low activity (i.e. <20 mCi) Iodine-125I (125I) interstitial radiotherapy was analyzed in patients with low-grade gliomas. MATERIALS AND METHODS: Permanent (247 patients) or temporary 125I-implants (268 patients) were used with a median reference dose of 60 Gy and 100 Gy, respectively, which was calculated to the outer rim of the tumour. The mean dose rate for temporary implants was low (median, 10 cGy/h). Risk factors were obtained from the multivariate proportional-hazards model. RESULTS: Radiogenic complications occurred in 39/515 patients (28 patients with transient symptoms and 11 patients with progressive symptoms). The most important risk factor was the volume of the intratumoural 200 Gy isodose. Available experimental data have associated a high dose zone in this range with the size of the treatment induced radionecrosis. Rapid tumour shrinkage (decrease of the tumour volume > or =50%) within the first 6 months with subsequent centripetal movement of non-pathologic tissue into the high dose zone and a reimplantation were additional risk factors. Radiation injury after rapid tumour shrinkage could be better avoided with temporary implants. A 200 Gy isodose volume <4.5 ml corresponded to an estimated risk of radiogenic complications <3%. There was a steep increase of the risk beyond this limit. Translation of the 200 Gy isodose volume in terms of the treatment volume and the reference dose allows rational treatment planning. The estimated risk of a temporary implant with an applied reference dose of 60 Gy and a treatment volume <23 ml was <3%. CONCLUSIONS: The intratumoural necrotizing effect of a low activity 125I implant limits its application to small treatment volumes. Radiation injury outside the treatment volume can be better avoided with temporary implants in the case of rapid tumour shrinkage.

Adolescent↗
PubMed1996

Stereotactic management of lesions of the pineal region.

OBJECTIVE: The relevance of the computed tomography-guided stereotactic approach for the management of lesions of the pineal region is analyzed. METHODS: In a retrospective analysis conducted between 1985 and 1993, the risk profile, the diagnostic accuracy, and the therapeutic relevance of the stereotactic approach in 106 patients was studied. Survival analysis was used to assess the reliability of the stereotactically obtained diagnosis in terms of follow-up observation. RESULTS: A histological diagnosis was obtained in 103 of the 106 patients. In three patients, a conclusive diagnosis could not be established because of intraoperative complications. One lesion was misdiagnosed as a pineocytoma instead of a pineoblastoma. Two of the 106 patients died; 9 patients experienced perioperative morbidity. In 38 patients, the stereotactic approach was also useful for therapy. Cyst aspiration and/or internal drainage was performed in 18 patients with symptomatic cystic lesions, and radiosurgical treatment with use of interstitial 125iodine was performed in 16 patients with low-grade tumors and in 4 patients with solitary metastases. In 12 patients, the obtained tissue diagnosis was the basis for deferring additional therapy. In 43 patients with germ-cell tumors, pineoblastomas, or malignant gliomas, a stereotactic biopsy was the starting point for additional radiotherapy/chemotherapy. Open tumor resection played a minor role (five patients). CONCLUSION: The stereotactic approach to the pineal region is a relatively safe procedure in experienced hands. The diagnosis obtained by computed tomography-guided stereotactic biopsy is a valid basis for treatment decisions. Long-term follow-up observation of the benign lesions is necessary for a definite confirmation of diagnostic accuracy.

Adolescent↗
PubMed1995

Interstitial iodine-125 radiosurgery for cerebral metastases.

The current study evaluates the efficacy of interstitial 125-iodine radiosurgery (brachytherapy) in 93 patients with circumscribed, spherical, mostly solitary metastases. In all patients the histological diagnosis was established by stereotactic biopsy. The treatment results of three therapeutic regimens have been examined retrospectively: Group A (38 patients) had interstitial radiosurgery with a reference tumour dose of 60 Gy in combination with percutaneous radiotherapy (40 Gy). Group B (34 patients) was treated by interstitial radiosurgery alone (reference dose 60 Gy). Group C (21 patients with recurrent metastases after previous radiotherapy/surgery) was treated by interstitial radiosurgery alone (reference dose 60 Gy). Median survival after interstitial radiosurgery was 17 months in group A, 15 months in group B, 6 months in group C. Favourable prognostic factors were a Karnofsky performance rating > or = 70, solitary metastasis, absence of disseminated disease, and a time interval > 1 year between diagnosis of the primary tumour and diagnosis of the cerebral metastases. Interstitial radiosurgery plus percutaneous radiotherapy did not prove to be superior to interstitial radiosurgery alone. No patient died of a locally irradiated metastasis. We conclude that interstitial radiosurgery achieves control of the growth of solitary spherical cerebral metastases in any location without radiation toxicity.

Adult↗
PubMed1995

Interstitial radiosurgery of low-grade gliomas.

The treatment of patients with low-grade gliomas remains a subject of controversy, especially with respect to new treatment modalities such as interstitial radiosurgery (brachytherapy), radiosurgery, and stereotactic radiotherapy. In a retrospective analysis conducted between 1979 and 1991, the authors studied the results of interstitial radiosurgery in 455 patients with low-grade gliomas (World Health Organization (WHO) Grade I+WHO Grade II) with regard to survival time, quality of life, the risk of malignant transformation, and the risk profile of the treatment concept. Interstitial radiosurgery with iodine-125 was performed using permanent (1979-1985) or temporary implants (after 1985) with low-dose rates (< or = 10 cGy/hr) and a reference dose of 60 to 100 Gy calculated to the outer rim of the tumor. The 5- and 10-year survival rates in patients with pilocytic astrocytomas (97 patients) were 84.9% and 83%, and in patients with WHO Grade II astrocytomas (250 patients) 61% and 51%, respectively. Five-year survival rates for patients with oligoastrocytomas (60 patients), oligodendrogliomas (27 patients), and gemistocytic astrocytomas (21 patients) were 49%, 50%, and 32%, respectively. In the group with WHO Grade II gliomas, young age and a good performance status were associated with a better prognosis. Unfavorable factors were midline shift, enhancement on computerized tomography (CT) scan, and tumor recurrence after previous radiotherapy or surgery. Tumor location had no influence on the prognosis (247 patients in this series had deep-seated tumors). Malignant transformation was the major cause of death. Important risk factors for malignancy were the patient's age, tumor enhancement in CT scan, and tumor recurrence after previous surgery or radiotherapy. Perioperative mortality was 0.9% and perioperative morbidity was 1.7%. Radiogenic complications were observed in 2.7% of all patients, most often in larger tumors and after using permanent implants. The authors conclude that interstitial radiosurgery represents a specific treatment modality for selected patients with unifocal circumscribed low-grade gliomas with a diameter of less than 4 cm in any location. The efficacy of this treatment lies in the same range as the best results after surgery and radiotherapy.

Adolescent↗
PubMed1994

Interstitial 125-iodine radiosurgery of low-grade gliomas of the insula of Reil.

Between 1979 and 1991 67 patients with low-grade gliomas of the insula (of Reil) were treated with 125-iodine interstitial radiosurgery. Retrospective analysis with a median follow-up of 55 months demonstrated a 5- and 10-year survival rate of 54% and 47%, respectively, for all low-grade gliomas treated and a 5- and 10-year survival rate of 57% for 49 patients with astrocytomas WHO grade II analysed separately. The median Karnofsky performance status of survivors was 90%. Malignant change was the cause of death in 85%, failure to control tumour growth in the remaining cases. Multivariate analysis with a Cox proportional hazard model identified solely the pre-operative Karnofsky performance score of 70-80 vs. 90% as a prognostic factor for outcome (p = 0.001, risk ratio 3.62), but not age, gender, tumour volume, length of disease before treatment, mode of implantation, or major vs. moderate or no shrinkage of tumour volume after interstitial radiosurgery. Thus, 125-iodine radiosurgery yielded survival rates in these deep-seated insular gliomas comparable to those reported after surgery and radiation therapy of lobar tumours. This was achieved with a low peri-operative mortality and morbidity and at low costs.

Adolescent↗