| 61. |
- Daşu, Alexandru, et al.
(författare)
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Superfractionation as a potential hypoxic cell radiosensitizer: prediction of an optimum dose per fraction
- 1999
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Ingår i: International Journal of Radiation Oncology, Biology, Physics. - 0360-3016 .- 1879-355X. ; 43:5, s. 1083-1094
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: A dose "window of opportunity" has been identified in an earlier modeling study (1) if the inducible repair variant of the LQ model is adopted instead of the pure LQ model, and if all survival curve parameters are equally modified by the presence or absence of oxygen. In this paper we have extended the calculations to consider survival curve parameters from 15 sets of data obtained for cells tested at low doses using clonogenic assays.METHODS AND MATERIALS: A simple computer model has been used to simulate the response of each cell line to various doses per fraction in multifraction schedules, with oxic and hypoxic cells receiving the same fractional dose. We have then used pairs of simulated survival curves to estimate the effective hypoxic protection (OER') as a function of the dose per fraction.RESULTS: The resistance of hypoxic cells is reduced by using smaller doses per fraction than 2 Gy in all these fractionated clinical simulations, whether using a simple LQ model, or the more complex LQ/IR model. If there is no inducible repair, the optimum dose is infinitely low. If there is inducible repair, there is an optimum dose per fraction at which hypoxic protection is minimized. This is usually around 0.5 Gy. It depends on the dose needed to induce repair being higher in hypoxia than in oxygen. The OER' may even go below unity, i.e. hypoxic cells may be more sensitive than oxic cells.CONCLUSIONS: If oxic and hypoxic cells are repeatedly exposed to doses of the same magnitude, as occurs in clinical radiotherapy, the observed hypoxic protection varies with the fractional dose. The OER' is predicted to diminish at lower doses in all cell lines. The loss of hypoxic resistance with superfractionation is predicted to be proportional to the capacity of the cells to induce repair, i.e. their intrinsic radioresistance at a dose of 2 Gy.
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| 62. |
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| 63. |
- Denekamp, Juliana, et al.
(författare)
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Inducible repair and the two forms of tumour hypoxia--time for a paradigm shift
- 1999
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 0284-186X .- 1651-226X. ; 38:7, s. 903-918
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Tidskriftsartikel (refereegranskat)abstract
- Clinical experience shows that there is a therapeutic window between 60 and 70 Gy where many tumours are eradicated, but the function of the adjacent normal tissues is preserved. This implies much more cell kill in the tumour than is acceptable in the normal tissue. An SF2 of 0.5 or lower is needed to account for the eradication of all tumour cells, while an SF2 of 0.8 or higher is needed to explain why these doses are tolerated by normal tissues. No such systematic difference is known between the intrinsic sensitivity of well-oxygenated normal and tumour cells. The presence of radioresistant hypoxic cells in tumours makes it even more difficult to understand the clinical success. However, there is experimental evidence that starved cells lose their repair competence as a result of the depletion of cellular energy charge. MRS studies have shown that low ATP levels are a characteristic feature of solid tumours in rodents and man. In this paper we incorporate the concept of repair incompetence in starving, chronically hypoxic cells. The increased sensitivity of such cells has been derived from an analysis of mammalian cell lines showing inducible repair. It is proportional to the SF2 and highest in resistant cells. The distinction between acutely hypoxic radioresistant cells and chronically hypoxic radiosensitive cells provides the key to the realistic modelling of successful radiotherapy. It also opens new conceptual approaches to radiotherapy. We conclude that it is essential to distinguish between these two kinds of hypoxic cells in predictive assays and models.
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| 64. |
- Ekblom, J, et al.
(författare)
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Elevated activity of semicarbazide-sensitive amine oxidase in blood from patients with skeletal metastases of prostate cancer.
- 1999
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Ingår i: Clinical science (London, England : 1979). - 0143-5221. ; 97:1, s. 111-5
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Tidskriftsartikel (refereegranskat)abstract
- The semicarbazide-sensitive amine oxidases constitute a group of copper-containing enzymes whose physiological function is unclear. The enzymes are present in various tissues, including blood plasma. At present, the source of the plasma enzyme in humans is not known. Results of a recent study suggested that semicarbazide-sensitive amine oxidase is expressed in the skeleton, e.g. in the spine. Using an indirect autoradiographic method in mice, we provide evidence that semicarbazide-sensitive amine oxidase is present in high abundance in bone tissue. Specific activities of semicarbazide-sensitive amine oxidase were estimated in blood samples from subjects with femoral bone fractures. Moreover, enzyme activities were also measured in patients suffering from prostate cancer with skeletal metastases. The level of specific semicarbazide-sensitive amine oxidase activity in serum was significantly elevated in patients with skeletal metastases compared with both healthy controls and patients having prostate cancer without signs of skeletal metastases. Based on the results of the present study, we propose that semicarbazide-sensitive amine oxidase in blood plasma may originate, at least in part, from the skeleton.
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| 65. |
- Ekström, Anna Mia, et al.
(författare)
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Occupational exposures and risk of gastric cancer in a population-based case-control study
- 1999
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Ingår i: Cancer Research. - 0008-5472. ; 59:23, s. 5932-5937
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Tidskriftsartikel (refereegranskat)abstract
- Gastric cancer trends seem to follow improvements in the environment of blue-collar workers, but the etiological role of occupational exposures in gastric carcinogenesis is scantily investigated. The risk of gastric adenocarcinoma in 10 common occupational industries, and particularly the long-term effects of asbestos, organic solvents, impregnating agents, insecticides, and herbicides, were evaluated in a population-based case- control study, including data on most established risk factors. The study base included all individuals of ages 40-79, born in Sweden and living in either of two areas (total population, 1.3 million) with differing gastric cancer incidences, from February 1989 through January 1995. We interviewed 567 cases classified to site (cardia/noncardia) and histological type, and 11(15 population-based controls, frequency-matched for age and sex. Metal workers had a 46% excess gastric cancer risk [adjusted odds ratio (OR), 1.46; 95% confidence interval (CI), 1.10-1.94], increasing to 1.65 (95% CI, 1.17- 2.32) for >10 years in the industry. The elevated risk after exposure to herbicides (OR, 1.56; 95% CI, 1.13-2.15) was attributable to phenoxyacetic acids (adjusted OR, 1.70; 95% CI, 1.16-2.48), similarly across tumor subtypes, and not modified by smoking, body mass index, or Helicobacter pylori. The absence of interaction was demonstrated by the pure multiplicative effect found among those exposed to both H. pylori and phenoxyacetic acids (OR, 3.42; 95% CI, 1.41-8.26). Organic solvents, insecticides, impregnating agents, and asbestos were not associated with gastric cancer risk. Employment in the metal industry and exposure to phenoxyacetic acids were both positively and independently associated with gastric cancer risk. The fractions of all gastric cancers attributable to these job-related exposures were small but not negligible (7 and 5%, respectively) in the Swedish population.
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| 66. |
- Elmroth, Kerstin, 1970, et al.
(författare)
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Influence of temperature on radiation-induced inhibition of DNA supercoiling
- 1999
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Ingår i: Radiat Res. - 0033-7587. ; 152:2, s. 137-43
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Tidskriftsartikel (refereegranskat)abstract
- The influence of subnormal temperatures (2, 15 and 28 degrees C) on the effects of radiation in MCF-7 cell cultures was studied using the fluorescent (halo) nucleoid assay. Increasing the propidium iodide (PI) concentration (0.5-7.5 microgram/ml PI) resulted in relaxation, i.e. in increasing nucleoid area; higher concentrations up to 50 microgram/ml caused rewinding that resulted in nucleoid contraction. Rewinding was inhibited by X irradiation (2, 4 and 8 Gy) in a dose-dependent way. Incubation at subnormal temperature did not influence the nucleoid area but did reduce radiation-induced inhibition of rewinding after 4 Gy. The low temperature (2 degrees C) during rather than prior to irradiation appeared to protect from radiation-induced inhibition of nucleoid rewinding. Decreased temperature during irradiation may change the conditions so as to reduce DNA- matrix damage induced by radiation.
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| 67. |
- Elomaa, I, et al.
(författare)
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Chemotherapy in Ewing's sarcoma. The Scandinavian Sarcoma Group experience
- 1999
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Ingår i: Acta Orthopaedica Scandinavica. Supplementum. - 0300-8827. ; 70:285, s. 69-73
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Tidskriftsartikel (refereegranskat)abstract
- During the past 15 years the Scandinavian Sarcoma Group has treated 140 patients with Ewing's sarcoma. Two protocols have been used. SSG IV included 52 patients between 1984 and 1990 and SSG IX, 88 patients since 1990. After 5 years of treatment, local recurrences occurred in 19% of the patients (M0 + M1) in the SSG IV group and 10% in the SSG IX group. Distant metastases developed in 57% of the M0-patients in the SSG IV group and in 33% in the SSG IX group. Tumor-related survival (overall) of M0-patients was 49% in SSG IV and 70% in SSG IX, and the metastasis-free survival rate 45% and 58%, respectively. Patients having a localized extremity tumor had a survival rate of 90% (SSG IX). In both treatment groups, good responders to chemotherapy had a better survival rate than poor ones (SSG IV, p < 0.02, GI-II vs. G II-IV and SSG IX, p < 0.003, GI-III vs. G IV). In conclusions local control and survival rates were better with SSG IX than SSG IV.
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| 68. |
- Fransson, Per, et al.
(författare)
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Late side effects unchanged 4-8 years after radiotherapy for prostate carcinoma : A comparison with age-matched controls
- 1999
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Ingår i: Cancer. - : John Wiley & Sons. - 0008-543X .- 1097-0142. ; 85:3, s. 678-688
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND. The authors of this study previously evaluated pelvic irradiation-induced late side effects in patients with localized prostatic carcinoma 4 years after external irradiation by administering a validated self-assessment questionnaire (QUFW94), and compared the results with those of age-matched controls. The current study was designed to evaluate prospectively the patients' problems 8 years after radiotherapy and to compare them with those reported by the same controls. METHODS. The questionnaire was sent out at a mean of 8 years (range, 72-104 months) after irradiation to 120 patients and 125 controls. For analysis of sexual function, the patient group was divided into two subgroups, one treated with radiotherapy only (RT) and one group treated with radiotherapy plus castration (RT+A). A value of >1 on a 0-10 scale indicated that the patient was having a problem. RESULTS, The mean age was 73 years for both patients and controls. No changes in urinary problems were seen between the 4-year and the 8-year follow-up in the 2 groups. Sixty percent and 54% of the patients (P = 0.096) and 24% and 31% of the controls (P = 0.988) reported urinary problems at the 4-year and 8-year follow-ups, respectively. No changes in gastrointestinal late side effects in the patient group were seen between the 4-year (65%) and the 8-year (62%) follow-ups (P = 0.490). However, there was a decrease in intestinal problems in the control group between the 4-year (12%) and the 8-year (9%) follow-ups (P = 0.001). The sexual problems did not change during the two periods, in the patient groups or in the control groups. Fifty-six percent and 65% of the RT group (P = 0.052), 67% and 54% of the RT + A group (P = 0.555), and 27% and 33% of the control group (P = 0.243) indicated some kind of sexual problem at the 4-year and 8-year follow-ups, respectively. CONCLUSIONS. The amount of pelvic irradiation-induced urinary late side effects, intestinal late side effects, and sexual function, evaluated with a self-assessment questionnaire, did not change between 4 and 8 years after RT. The age-matched controls reported no change in urinary or sexual problems despite advanced age, but there was a reported decrease in intestinal problems, Cancer 1999;85:678-88. (C) 1999 American Cancer Society.
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| 69. |
- Gestblom, C, et al.
(författare)
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The basic helix-loop-helix transcription factor dHAND, a marker gene for the developing human sympathetic nervous system, is expressed in both high- and low-stage neuroblastomas
- 1999
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Ingår i: Laboratory Investigation. - 1530-0307 .- 0023-6837. ; 79, s. 67-
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Tidskriftsartikel (refereegranskat)abstract
- Neuroblastoma is derived from the sympathetic nervous system and might arise as a result of impaired differentiation, retaining the neuroblastic tumor cells in the cell cycle. Thus, to understand the genesis of neuroblastoma, the study of mechanisms and genes regulating normal sympathetic development is of potential interest. The basic helix-loop-helix transcription factors human achaete-scute homolog-1 (HASH-1) and deciduum, heart, autonomic nervous system, and neural crest derivatives (dHAND) are expressed in the sympathetic nervous system of embryonic mice and chicken, with undetectable postnatal expression. By in situ hybridization technique, we show that dHAND was expressed by human sympathetic neuronal and extra-adrenal chromaffin cells throughout embryonic and fetal life, and was initially expressed in immature chromaffin cells of the adrenal gland. With overt chromaffin differentiation, dHAND was down-regulated. HASH-1, in contrast, was expressed in human sympathetic cells only at the earliest embryonic ages examined (Week 6.5 to 7). All examined neuroblastoma specimens (25/25) and all cell lines (5/5) had detectable dHAND mRNA levels. HASH-1 expression in tumor specimens was more restricted, although all cell lines (5/5) were HASH-1-positive. These results show that neuroblastoma tumors have retained embryonic features, suggesting that many neuroblastomas are blocked at an early stage of normal development when HASH-1 and dHAND are expressed. dHAND also appears to be a reliable and potentially useful clinical diagnostic marker for neuroblastoma, because expression was not dependent on tumor or differentiation stages and other pediatric tumors were dHAND-negative.
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| 70. |
- Gustafson, Pelle, et al.
(författare)
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Prognostic implications of various models for calculation of S-phase fraction in 259 patients with soft tissue sarcoma
- 1999
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Ingår i: British Journal of Cancer. - : Springer Science and Business Media LLC. - 1532-1827 .- 0007-0920. ; 79, s. 1205-1209
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Tidskriftsartikel (refereegranskat)abstract
- The S-phase fraction (SPF) in flow cytometric DNA histograms in soft tissue sarcoma (STS) can be calculated in various ways. The traditional planimetric method of Baisch has been shown to be prognostic, but is hampered by a failure rate of around 40%. We therefore tested other models to see if this rate could be decreased with retained prognostic value. In 259 STS of the locomotor system the SPF was calculated according to Baisch and with commercial parametric MultiCycle software using different corrections for background. Using the Baisch model, 159 histograms could be evaluated for SPF. The 5-year metastasis-free survival rate (MFSR) was 0.94 for the low-risk group (defined with SPF), and 0.53 for the high-risk group. In the low-risk group, four of the seven patients who developed metastasis did so after 5 years Using the MultiCycle software, SPF could be calculated in 253 tumours. Depending on type of background correction used, the 5-year MFSR varied between 0.67 and 0.82 for the low-risk group, and between 0.47 and 0.53 for the high-risk group. The late metastasis pattern in the low-risk group was never seen using the MultiCycle software. We conclude that in paraffin archival material, calculation of SPF according to Baisch is preferable in clinical use due to better separation between low-risk and high-risk groups, and also the possibility to identify patients who metastasize late.
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