Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.3.1.51 (HDR)
 605 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The outcome of a course of radiotherapy is very dependent on the dose per fraction. The smaller the dose per fraction, as a general rule, the better the sparing of the late reacting normal tissues. 2. Overall treatment time is important, especially for tumours with a rapid doubling time. In such a case, the ideal of small doses per fraction (to save late reacting tissues) as well as a short overall treatment time (to offset the effect of repopulating) can be achieved by small doses per fraction applied two to three times per day, including Saturdays or weekends. 3. The BED (biologically effective dose) is a simple to use formula indicating the effects of fractionation. The most important term in the formula is the alpha/beta ratio which is available from experimental work for many tumours and tissues and can be looked up. As a guide, an alpha/beta ratio of 10 for early (acute) reaction and for tumour effects, and an alpha/beta ratio of 2 for late effects plus normal tissue complications can be used. 4. The application of the BED demonstrates that for HDR intracavitary therapy for cervical carcinoma, the biologically relevant dose lateral to point M(A) falls very much more rapidly than the nominal dose. Line sources are shown by comparison with other published reports, not to be intrinsically inferior to tandem ring/tandem ovoid systems and may have advantages the more cumbersome systems do not have, and may have the large advantage of allowing multiple small fractions without anaesthesia. For the particular line source system under discussion, water in a 40 cm3 Foleys bulb is used as the protecting medium for the posterior bladder wall and the anterior rectum. This particular system allows fraction sizes far smaller than 9.1 Gy at point (M)A, e.g. 3 Gy, which bestows an even greater benefit in terms of the therapeutic ratio according to BED10 and BED2 calculations.
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PMID:Radiation related prognostic factors in radiation oncology. 1072 10

The aim of this study was to evaluate the symptomatic and endoscopic responses as well as the toxicities in 158 patients with endobronchial lung cancer treated with high dose rate endobronchial brachytherapy (HDR-EB). Forty-three patients with stage III NSCLC were treated with 60Gy external beam radiotherapy (ERT) and three applications of 5Gy each of HDR-EB (group A). Seventy-four patients who did not receive previous RT were treated with 30Gy ERT and two applications of 7.5Gy HDR-EB with palliative intent (group B). Forty-one patients with recurrent tumor who were irradiated previously were treated with three applications of 7.5Gy HDR-EB, with palliative intent (group C). In group A, bronchoscopic complete (CR) and overall response rates (ORR) were 67% and 86%, respectively. Symptomatic improvement was obtained in 58% of patients with cough, 77% of patients with dyspnea and 100% of patients with hemoptysis. Two and 5-year survival rates were 25.5% and 9.5%, respectively and the median survival time (MST) was 11 months. In group B, the bronchoscopic CR and ORR were 39% and 77%, respectively and 28% and 72% in group C. The symptomatic response rates were 57% and 55% for cough, 90% and 78% for dyspnea and 94% and 77% for hemoptysis, with a MST of 7 and 6 months in Groups B and C, respectively. Eighteen patients (11%) died of fatal hemoptysis (FH) with the median time to this event of 7 months. Treatment intent (p<0.001), total BED (p<0.001) and the number of HDR-EB fractions (p<0.001) were significant prognostic factors for FH. HDR-EB provides effective palliation in relieving the symptoms of patients with endobronchial lung cancer, however, there is a risk of developing FH that is associated with a high BED and multiple HDR-EB applications.
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PMID:High dose rate endobronchial brachytherapy in the management of lung cancer: response and toxicity evaluation in 158 patients. 1848 80

The aim of this work is to examine the influence of the dose optimization procedure on the value of radiation doses in organs of risk and to compare value of doses measured in healthy tissues according to chosen different PDR brachytherapy (PDRBT) and HDR brachytherapy (HDRBT) fractionation schedule. Fifty one patients treated with PDRBT were qualified for calculations. This group included patients with head and neck cancer, brain tumor, breast cancer, sarcoma, penile cancer and rectal cancer. The doses were calculated in chosen critical points in surrounded healthy tissues. For all treatment plans the doses were compared with the use of the BED (Biologically Equivalent Dose) formula and PDR along with HDR values were calculated. Differences among total doses in PDRBT and different schemas of HDRBT in critical points before and after dose point and volume optimization, were analyzed. The same dependences were examined also for BEDs. One ascertained that in biologic equivalent (to PDR) HDRBT the increase of fraction dose from 4 Gy to 10 Gy caused the necessity of decrease of total dose in treatment area (p<0,001). The use of HDR instead of PDR essentially lowered physical and biological doses in examined organs of risk. In many examined critical points in organs of risk where biological equivalence dose in the treatment area was the same, one ascertained the decrease of total physical HDR dose according to the growth of the fraction dose. Similar dependences appeared also for biologically equivalent doses. The optimization process in PDRBT improved the dose homogeneity in the treatment area, but simultaneously induced unprofitable (essential statistically) increase of dose in some healthy organs of risk, what makes an increase risk for radiation-induced complications. The use of biologically equivalent HDRBT instead of PDRBT makes for the decrease of physical doses in the treatment area and the decrease of physical and biologically equivalent doses in healthy organs of risk.
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PMID:Optimization and it's influence on value of doses in HDR and PDR brachytherapy. 2042 30