International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Mar 2001
The local field in infratentorial ependymoma: does the entire posterior fossa need to be treated?
In the past decade, there have been multiple reports indicating that the predominant problem in the curative treatment of intracranial ependymoma is local failure. As a result, many have recommended local field radiotherapy. For infratentorial ependymoma, there is controversy regarding what constitutes the local field. Some radiation oncologists advocate coverage of the entire posterior fossa, whereas others recommend radiotherapy to the tumor bed and a safety margin. ⋯ For nondisseminated, low-grade infratentorial ependymoma, the radiotherapy volume does not need to include the entire posterior fossa. This information can be used to minimize late effects of RT in the era of three-dimensional (conformal) radiotherapy. No conclusion can be reached regarding the appropriate local field for high-grade infratentorial ependymoma because of the small number of patients.
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Int. J. Radiat. Oncol. Biol. Phys. · Feb 2001
Individualization of dose prescription based on normal-tissue dose-volume and radiosensitivity data.
The aim of this paper is to illustrate the potential gain in tumor control probability (TCP) of prostate cancer patients by individualizing the prescription dose according to both normal-tissue (N-T) dose-volume and radiosensitivity data. ⋯ There is a potential gain (increase in local tumor control) from dose individualisation strategies based on both N-T dose-volume data and radiosensitivity (assuming that this is available). Dose prescription individualization based only on dose-volume data can be exploited provided that reliable N-T response models are available. There will be additional gains if some estimate of N-T radiosensitivity is available to allow further patient stratification, identification of patients with high radiosensitivity being particularly important.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 2001
High-dose-rate brachytherapy may be radiobiologically superior to low-dose rate due to slow repair of late-responding normal tissue cells.
Recent analysis of morbidity for patients treated with the continuous hyperfractionated accelerated radiotherapy (CHART) regimen demonstrates that repair half-times for late-reacting normal tissue cells are of the order of 4-5 h, which is considerably longer than previously believed. This would reduce repair of these tissue cells during a course of low-dose rate (LDR) brachytherapy, but have no effect at high-dose-rate (HDR), where there is no repair during, and full repair between fractions, regardless of repair half-time. The effect this has upon radiobiologic comparison of LDR and HDR is the topic of this paper. ⋯ The previously held belief that LDR must be inherently superior radiobiologically to HDR is wrong if the long repair times demonstrated in the recent CHART study are applicable to other late-reacting normal tissues. This could explain why HDR has been so successful in clinical practice, especially for the treatment of cervical cancer, despite previous convictions of radiobiologic inferiority of this modality.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 2001
Clinical TrialPhase II prospective study of the use of conformal high-dose-rate brachytherapy as monotherapy for the treatment of favorable stage prostate cancer: a feasibility report.
To evaluate the technical feasibility and tolerance of image-guided transperineal conformal high-dose-rate (C-HDR) brachytherapy as the sole treatment modality for favorable, localized cancer of the prostate, and to analyze possible intrafraction and interfraction volume changes in the prostate gland which may affect dosimetric quality. ⋯ Our protocol using C-HDR interstitial brachytherapy as monotherapy for early cancer of the prostate was feasible and well tolerated by 41 patients treated. Changes in interfraction prostate volume do not appear to be significant enough to warrant modification of dosimetry for each fraction. Both excellent dose coverage of the prostate gland and low urethral dose are achieved as measured by DVH. However, paramount attention should be given to needle displacement before each fraction. Needle movement is most significant between fractions 1 and 2. Acute toxicity (RTOG) has been modest. Late toxicity and tumor control rates will be reported as longer follow-up allows.
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Int. J. Radiat. Oncol. Biol. Phys. · Jan 2001
Extracranial radiosurgery: immobilizing liver motion in dogs using high-frequency jet ventilation and total intravenous anesthesia.
Extracranial radiosurgery requires control of organ motion. The purpose of this study is to quantitatively determine the extent of liver motion in anesthetized dogs with continuous i.v. propofol infusion with or without muscle relaxants and high-frequency jet ventilation. ⋯ The liver motion in each anesthetized dog was controlled under 3.0 mm in all directions with the use of high-frequency jet ventilation. No detectable advantage was identified by the injection of muscle relaxant in terms of further reducing the liver motion. The preclinical animal study indicated that the use of high-frequency jet ventilation (HFJV) would be able to limit the liver motion to an extent acceptable for the application of extracranial radiosurgery in humans. Radiosurgery for localized liver tumors warrants further investigation.