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- Mattsson, Sören, et al.
(författare)
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Swedish Cancer Society radiation therapy research investigation
- 2002
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 41:7-8, s. 596-603
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Tidskriftsartikel (refereegranskat)abstract
- In an investigation by the Swedish Cancer Society, the present status, critical issues and future aspects and prospects were described by an expert group for each of nine major areas of radiation research. A summary of the investigation is presented in this report. A more extensive summary (in Swedish) can be found at www.Cancerfonden.se. It is concluded that radiation therapy plays an increasingly important role in curative and palliative tumour treatment and presents a considerable challenge to research. Several suggestions are made that could improve the possibilities for high-quality radiation therapy research in Sweden.
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| 3. |
- Denekamp, Juliana, et al.
(författare)
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Hyperfractionation as an effective way of overcoming radioresistance
- 1998
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Ingår i: International Journal of Radiation Oncology, Biology, Physics. - 0360-3016 .- 1879-355X. ; 42:4, s. 705-709
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To model the influence of hypoxic radioprotection in fractionated treatments over a range of fraction sizes. To determine whether there is a "therapeutic window" of dose per fraction where hypoxic radioresistance could be reduced, and if so, where it occurs in different cell lines. MATERIALS AND METHODS: A mathematical model has been used to simulate the response of cells to low doses of radiation, in the region of clinical interest. We have used the inducible repair variant of the linear quadratic (LQ) equation, with a hypersensitive region (alphaS) at low doses that gradually transforms to the accepted "resistance" in the shoulder region (alphaR). It contains two new parameters, the ratio alphaS/alphaR, and D(C). We have accepted that the "induction dose" D(C) is modified by anoxia to the same extent as the other parameters. We have initially modeled using theoretical parameters and then checked the conclusions with 14 sets of published experimental data for cell lines investigated for inducible repair. RESULTS: We have computed the clinical hypoxic protection (OER') as a function of dose per fraction in simulations of clinical fractionated schedules. We have identified a therapeutic window in terms of dose per fraction at about 0.5 Gy, where the OER' is minimized, regardless of the precise cell survival curve parameters. The minimum OER' varies from one cell line to another, falling to about 1.0 if alphaS/alphaR = 6-10 and even far below 1.0 if alphaS/alphaR > or = 20. DISCUSSION: Hyperfractionation using 0.5 Gy fractions may therefore be more effective than oxygen mimetic chemical sensitizers, since it could even make some tumor cells more sensitive than oxic normal tissues. The tumor lines that benefit most from this type of sensitization are those with the highest intrinsic oxic radioresistance, i.e. those with high SF2 values.
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| 5. |
- Franzén, Lars, et al.
(författare)
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Fractionated irradiation and early changes in noradrenaline induced potassium efflux(86Rb+) in rat parotid gland
- 1992
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Ingår i: Acta Oncologica. - 0284-186X .- 1651-226X. ; 31:3, s. 359-364
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Tidskriftsartikel (refereegranskat)abstract
- The effects of fractionated irradiation on the electrolyte fluid secretion from rat parotid gland were studied. Secretion was measured as noradrenaline stimulated potassium efflux in vitro with Rb-86+ as tracer for potassium. The irradiation was delivered either as a five-day schedule (total dose 20, 25, 30, 35, 40, 45 Gy) or a two-day schedule (total dose 24, 32 Gy). The noradrenaline stimulated efflux was decreased in comparison with contralateral controls 10 days after the last irradiation. The effect was dose-dependent. Based on the data available, alpha/beta ratio of the used system was calculated to about 20 Gy, which corresponds to other results regarding early radiation effects.
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| 6. |
- Franzén, Lars, et al.
(författare)
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Fractionated-irradiation and late changes in rat parotid-gland : effects on the number of acinar-cells, potassium efflux, and amylase secretion
- 1993
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Ingår i: International Journal of Radiation Biology. - : Informa UK Limited. - 0955-3002 .- 1362-3095. ; 64:1, s. 93-101
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Tidskriftsartikel (refereegranskat)abstract
- Irradiation of head- and neck cancer commonly results in oral dryness and discomfort for the patients due to salivary gland damage. The exact mechanisms behind the inherent radiosensitivity of salivary glands remain to be elucidated. In the present study, we used different in vitro secretory models and quantitative morphological characterization of rat parotid gland following fractionated unilateral irradiation to one gland on a 5-day fraction schedule (Monday-Friday) with 6 MV photons (total dose 30, 35, 40 and 45 Gy) or a two-fractions regimen in 5 days (Monday and Friday) with total dose of 24 and 32 Gy. The contralateral shielded gland served as control, and parallel analyses of irradiated and control glands were performed 180 days following the last irradiation treatment. The relative noradrenaline stimulated electrolyte secretion (rubidium-86 tracer for potassium) was decreased in the irradiated compared with control glands. The noradrenaline-stimulated exocytotic amylase release was not significantly affected by irradiation, but the gland content of amylase was decreased dose-dependently. The quantitative morphological analysis revealed a dose-dependent decline in the number of acinar cells, whereas the other parenchymal cells (intercalated, striated- and excretory duct cells) were un-, affected by the irradiation compared with control glands.
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| 7. |
- Hörnsten, Carl, et al.
(författare)
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High blood pressure as a risk factor for incident stroke among very old people : a population-based cohort study
- 2016
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Ingår i: Journal of Hypertension. - 0263-6352 .- 1473-5598. ; 34:10, s. 2059-2065
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: High blood pressure (BP) increases the risk of stroke, but there is limited evidence from studies including very old people. The aim was to investigate risk factors for incident stroke among very old people.METHODS: A prospective population-based cohort study was performed among participants aged at least 85 years in northern Sweden. The 955 participants were tested at their homes. BP was measured manually after 5-min supine rest. Incident stroke data were collected from medical charts guided by hospital registry, death records, and 5-year reassessments. Cox proportional hazards models were used.RESULTS: The stroke incidence was 33.8/1000 person-years (94 stroke events) during a mean follow-up period of 2.9 years. In a comprehensive multivariate model, atrial fibrillation [hazard ratio 1.85, 95% confidence interval (CI) 1.07-3.19] and higher SBP (hazard ratio 1.19, 95% CI 1.08-1.30 per 10-mmHg increase) were associated with incident stroke overall. However, higher SBP was not associated with incident stroke in participants with SBP less than 140 mmHg (hazard ratio 0.90, 95% CI 0.53-1.53 per 10-mmHg increase). In additional multivariate models, DBP at least 90 mmHg (hazard ratio 2.45, 95% CI 1.47-4.08) and SBP at least 160 mmHg (vs. <140 mmHg; hazard ratio 2.80, 95% CI 1.53-5.14) were associated with incident stroke. The association between BP and incident stroke was not affected by interactions related to sex, dependence in activities of daily living, or cognitive impairment.CONCLUSION: High SBP (≥160 mmHg) and DBP (≥90 mmHg) and atrial fibrillation appeared to be risk factors for incident stroke among very old people.
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| 10. |
- Weidung, Bodil, et al.
(författare)
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Blood Pressure, Gait Speed, and Mortality in Very Old Individuals : A Population-Based Cohort Study
- 2015
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Ingår i: Journal of the American Medical Directors Association. - : Elsevier BV. - 1525-8610 .- 1538-9375. ; 16:3, s. 208-214
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Clinical trials and observational studies have produced contradictory results regarding the association of blood pressure (BP) and mortality in people aged 80 years or older. Gait speed at usual pace has been shown to moderate this association in a population of noninstitutionalized people aged 65 years or older. The aims of this study were to investigate the association of BP with all-cause mortality in a representative sample of people aged 85 years or older and to assess whether gait speed moderates this association.Design, Setting, and Participants: A total of 806 participants in the population-based prospective Umeå 85+/GERDA study aged 85, 90, and 95 years or older.Measurements: Gait speed at usual pace was measured over 2.4 m. The main outcome was hazard ratios (HRs) for all-cause mortality according to systolic and diastolic BP categories in the total sample and in faster-walking (≥0.5 m/s, n = 312) and slower-walking (<0.5 m/s, n = 433) subcohorts; the latter also included habitually nonwalking participants. Comprehensive adjustments were made for sociodemographic and clinical characteristics associated with death.Results: Mean age and baseline systolic and diastolic BP were 89.6 ± 4.6 years, 146.8 ± 23.9 mm Hg, and 74.8 ± 11.1 mm Hg, respectively. Most (n = 561 [69%]) participants were women, 315 (39%) were care facility residents, and 566 (70%) were prescribed BP-lowering drugs. Within 5 years, 490 (61%) participants died. In the total sample and slower-walking subcohort, systolic BP appeared to be inversely associated with mortality, although not independent of adjustments. Among faster-walking participants, mortality risk after adjustment was more than 2 times higher in those with systolic BP of 140 to 149 mm Hg (HR = 2.25, 95% confidence interval [CI] = 1.03–4.94) and 165 mm Hg or higher (HR = 2.13, 95% CI = 1.01–4.49), compared with systolic BP of 126 to 139 mm Hg. Mortality risk was also independently higher in faster-walking participants with diastolic BP higher than 80 mm Hg, compared with diastolic BP of 75 to 80 mm Hg (HR = 1.76, 95% CI = 1.07–2.90).Conclusion: The gait speed threshold of 0.5 m/s may be clinically useful for the distinction of very old people with and without increased all-cause mortality risk due to elevated systolic and diastolic BP.
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