International journal of radiation oncology, biology, physics
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 1998
Case Reports Randomized Controlled Trial Clinical TrialTemporal lobe (TL) damage following surgery and high-dose photon and proton irradiation in 96 patients affected by chordomas and chondrosarcomas of the base of the skull.
To determine the temporal lobe (TL) damage rate in 96 patients treated with high-dose proton and photon irradiation for chordomas and chondrosarcomas of the base of the skull. ⋯ The 2- and 5-year cumulative TL damage rates were 7.6 and 13.2%, respectively. Despite the different TL damage rates related to age, tumor volume, number of surgical procedures prior to radiation therapy, and prescribed doses to the tumor, only gender was a significant predictor of damage (p = 0.0155) using a univariate (log rank) test. Chordomas and chondrosarcomas of the base of the skull may represent an interesting model to evaluate the TL damage rates because of their extradural origin, displacing the white matter instead of infiltrating it as gliomas do, because of their longer local recurrence-free survival other than gliomas and other brain tumors and because of the high doses of irradiation delivered to the target volume to obtain local control.
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 1998
Estimation of the incidence of late bladder and rectum complications after high-dose (70-78 GY) conformal radiotherapy for prostate cancer, using dose-volume histograms.
To investigate whether Dose-Volume Histogram (DVH) parameters can be used to identify risk groups for developing late gastrointestinal (GI) and genitourinary (GU) complications after conformal radiotherapy for prostate cancer. ⋯ These data show that dose escalation up to 78 Gy, using a conformal technique, is feasible. However, these data have also demonstrated that the incidence of severe late rectal bleeding is increased above certain dose-volume thresholds.
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No dose-response study has ever been performed for I-125 prostate implants using modern techniques of implant evaluation and modern treatment outcome end points. The amount of activity per volume implanted was increased over time based on review of postimplant dosimetry. This resulted in different delivered dose levels. This study explores the relationship between dose, biochemical failure, and biopsy results. ⋯ A dose response was observed at a level of 140 Gy. Adequate I-125 implants should deliver a dose of 140-160 Gy using TG43 guidelines.
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 1998
Pulse frequency in pulsed brachytherapy based on tissue repair kinetics.
Investigation of normal tissue sparing in pulsed brachytherapy (PB) relative to continuous low-dose rate irradiation (CLDR) by adjusting pulse frequency based on tissue repair characteristics. ⋯ Within the benchmark of the LQ model, advantage in normal tissue-sparing is expected when matching the pulse frequency to the repair kinetics of the normal tissue exposed. A period time longer than 1 h may lead to a reduction of late normal tissue complications. This theoretical advantage emphasizes the need for better knowledge of human tissue-repair kinetics.
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Int. J. Radiat. Oncol. Biol. Phys. · Apr 1998
Sublethal damage repair times for a late-responding tissue relevant to brachytherapy (and external-beam radiotherapy): implications for new brachytherapy protocols.
Data were analyzed from recent experiments with the end point of late rectal obstruction in rats, involving acute and various protracted radiation exposures. Because the end point is of direct relevance both for brachytherapy as well as external beam radiotherapy, the goal was to estimate the linear-quadratic (LQ) parameters alpha/beta and T1/2, which are of importance for designing improved protraction/fractionation schemes. ⋯ The long estimated repair time for a late-responding normal-tissue end point with direct relevance to brachytherapy suggests a variety of possible brachytherapy protocols that may be more efficacious than continuous low dose rate irradiation. Just as a difference in alpha/beta ratios between early- and late-responding tissues are a central tenet in radiotherapy, so corresponding differences in T1/2 values have the potential to be exploited, particularly for brachytherapy.