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At least 631 records · Page 35Linked to original sources
PubMed1990

Radiation therapy for early glottic cancer (T1N0M0): II. Prospective randomized study concerning radiation field.

A prospective randomized study to determine the effect of radiation field on the local control of early glottic cancer was performed. From May 1982 through December 1985, a total of 87 patients with early glottic cancer (T1N0M0) were treated at our department with an individualized wedge filter technique using a shell to improve the dose distribution and immobilization during radiotherapy with 4 MV X ray. Patients were randomly allocated to either treatment group A (radiation field size: 5 x 5 cm2) or B (6 x 6 cm2) using bilateral parallel opposed portals. Total radiation dose administered was 60 Gy in 30 fractions over a 6-week period. The 3-year recurrence-free survival rates were 93% in group A and 96% in group B (no significant difference). Comparison with historical control showed that both arms achieved better results. These results were mainly due to the improved local control of whole-length lesions of single vocal cords. Acute mucosal reaction (p less than 0.05) and persistent arytenoid edema lasting more than 6 months (p less than 0.02) were more frequently observed in group B than in group A. It is concluded that the critical factor in getting optimal results in the treatment of early glottic cancer is careful attention to the technique of treatment.

Adult↗
PubMed1994

Radiation induction of immediate early genes: effectors of the radiation-stress response.

Recent studies have demonstrated that the early response genes c-jun, Egr-1, c-fos, and NF kappa B are induced following exposure of mammalian cells to ionizing radiation. We propose that the products of these early response genes regulate downstream genes that are important in the adaptation of cells and tissues to radiation-induced stress. Potential downstream targets include cytokine and growth factor genes as well as deoxyribonucleic acid (DNA) repair genes. Early response gene products may also regulate cell cycle progression following cellular x-irradiation. Signal transduction pathways that allow cells to adapt to radiation may provide molecular targets to modify tumor and normal responses to radiotherapy.

Animals↗
PubMed2005

[New strategies to interfere with radiation response: "biomodulation" of radiation therapy].

The development of several new anti cancer agents has been made possible because of recent significant achievements in our global understanding of cancer biology. These new "targeted" agents selectively inhibit targets necessary for tumor cell growth and viability with little toxicity to normal cells compared to conventional cytotoxic agents. So far, the efficacy of many of these new promising agents when used alone treatment remains limited, it is likely that the optimal use of these agents could be obtained in combination with conventional agents such as radiation therapy. The potential benefit of these targeted therapies combined with irradiation seems important. They might offer the advantage of increasing the tumor response to radiation with no or little increase in normal tissue damage. Therefore, these new types of chemo-radiation approaches might respect the normal tissue versus tumor cell "therapeutic ratio". These approaches can be sub divided in three sub groups: 1) Therapeutics targeting selectively one tumor related biochemical activity such as EGFR inhibitors. These approaches are efficient but one mutation of the target might render them inefficient. 2) Therapeutics directed against a widely expressed target. This is the case for anti Insulin Growth Factor-1 (IGF1R) interventions: IGF1R inhibition seems to specifically alter tumor cell viability with a minimal effect on normal cells viability. 3) Strategies which are not targeted against the tumor but the microenvironment, especially angiogenesis. This type of approaches seems to be applicable independently of tumor intrinsic biologic related factors.

Angiogenesis Inhibitors↗
PubMed2005

Radiation oncology practice accreditation: the American College of Radiation Oncology, Practice Accreditation Program, guidelines and standards.

The American College of Radiation Oncology Practice Accreditation Program (ACRO PAP) is a process by which a medical practice is evaluated through an in depth external review to ascertain whether or not key components of the practice comply with existing regulations, rules, laws, practice guidelines and professional practice standards. In radiation oncology, like other fields, it is driven by the need or desire to demonstrate an identified level of patient care. The accreditation process adopted by the American College of Radiation Oncology (ACRO) is based on the parameters of quality care assessment outlined by the National Academy of Science's Institute of Medicine. Those practices that meet these criteria are eligible for recognition and accreditation by ACRO.

Accreditation↗
PubMed2004

The radiation doses to erectile tissues defined with magnetic resonance imaging after intensity-modulated radiation therapy or iodine-125 brachytherapy.

PURPOSE: To report penile bulb (PB) and corporal bodies (CB) doses during intensity-modulated radiation therapy (IMRT) and permanent (125)I prostate implant alone (BT) for favorable, early stage, clinically localized prostate cancer using computed tomography (CT) and magnetic resonance imaging (MRI) to provide a basis for comparison as the initial report of a comprehensive project to develop erectile tissues sparing techniques. METHODS AND MATERIAL: Prostate, PB and CB volumes were defined by a fused CT/MRI simulation study performed before treatment in 29 IMRT patients and verification study performed 30 days postimplant in 15 BT patients. The median prescribed prostate dose for the IMRT and BT groups was 74 Gy and 145 Gy, respectively. Dose volume histograms (DVHs) were generated to determine the dose characteristics for the PB, CB, and prostate for each patient. D(90), V(100), and V(50) were used, where D(i) was defined as the dose that covers i% of the prostate volume and V(i) is the fractional volume of the prostate that receives i% of the prescribed dose. The Wilcoxon rank sum test was used to evaluate significance between the groups. RESULTS: The median PB D(90), V(100), and V(50) values were 17.5 Gy, 0%, and 31.9% for the IMRT group; and 52.5 Gy, 21.5%, and 89.7% for the BT group. The median CB D(90), V(100), and V(50) values were 7.3 Gy, 0%, and 0.9% for the IMRT group; and 26.9 Gy, 2.4%, and 20.1% for the BT group. The differences between the IMRT vs. BT V(100) values, but not V(50), were statistically significant for the PB (p = 0.001) and CB (p = 0.001). CONCLUSIONS: Radiation dose to the PB and CB is low with IMRT or BT. Magnetic resonance imaging is superior to CT for the imaging of erectile tissues. Intensity-modulated radiation therapy may offer further reductions in the doses received by the PB and CB; however, at what cost to prostate coverage and normal tissue sparing will be the subject of a follow-up study.

Aged↗
PubMed2006

Cerebral radiation necrosis: incidence, outcomes, and risk factors with emphasis on radiation parameters and chemotherapy.

PURPOSE: To investigate radiation necrosis in patients treated for glioma in terms of incidence, outcomes, predictive and prognostic factors. METHODS AND MATERIALS: Records were reviewed for 426 patients followed up until death or for at least 3 years. Logistic regression analysis was performed to identify predictive and prognostic factors. Multivariate survival analysis was conducted using Cox proportional hazards regression. Separate analyses were performed for the subset of 352 patients who received a biologically effective dose (BED) > or =85.5 Gy2 (> or =45 Gy/25 fractions) who were at highest risk for radionecrosis. RESULTS: Twenty-one patients developed radionecrosis (4.9%). Actuarial incidence plateaued at 13.3% after 3 years. In the high-risk subset, radiation parameters confirmed as risk factors included total dose (p < 0.001), BED (p < 0.005), neuret (p < 0.001), fraction size (p = 0.028), and the product of total dose and fraction size (p = 0.001). No patient receiving a BED <96 Gy2 developed radionecrosis. Subsequent chemotherapy significantly increased the risk of cerebral necrosis (p = 0.001) even when adjusted for BED (odds ratio [OR], 5.8; 95% confidence interval [CI], 1.6-20.3) or length of follow-up (OR, 5.4; 95% CI, 1.5-19.3). Concurrent use of valproate appeared to delay the onset of necrosis (p = 0.013). The development of radionecrosis did not affect survival (p = 0.09). CONCLUSIONS: Cerebral necrosis is unlikely at doses below 50 Gy in 25 fractions. The risk increases significantly with increasing radiation dose, fraction size, and the subsequent administration of chemotherapy.

Adult↗
PubMed2004

Updated European core curriculum for radiotherapists (radiation oncologists). Recommended curriculum for the specialist training of medical practitioners in radiotherapy (radiation oncology) within Europe.

AIM: To produce updated state-of-the-art recommendations for harmonised medical specialist training in radiotherapy within Europe. MATERIAL AND METHODS: The Minimum Curriculum for the Theoretical Education in Radiation Oncology in Europe from 1991 was updated under consideration of new developments in medicine in general, and in radiotherapy and its basic sciences in particular. Recent medical developments, national guidelines and training programmes from European countries, as well as equivalent documents from the USA and Australia were reviewed by an expert panel jointly appointed by the European Society of Therapeutic Radiology and Oncology and the European Board of Radiotherapy. A draft document prepared by this group was circulated among the national and professional societies for radiotherapy in Europe for review before a European consensus conference took place in Brussels in December 2002. RESULTS: The updated European Core Curriculum for Radiotherapists (Radiation Oncologists) was endorsed by representatives of 35 European nations during the Brussels consensus conference on December 14, 2002. Compared to the earlier version the updated document contains specific recommendations not only for the 5 year training curriculum but also for organisatoric and infrastructural aspects of teaching departments, and for supplementation of the training by formal teaching courses. CONCLUSION: The updated European core curriculum is an important step on the way to fully harmonise medical specialist training in Europe and to guarantee equal access for all European citizens to highest quality medical care. The responsibility for the implementation of the standards and guidelines set in the updated Core Curriculum for radiotherapy (radiation oncology) will lie with the local and/or national training bodies and authorities.

Clinical Competence↗
PubMed2003

Radiation optic neuropathy after external beam radiation therapy for acromegaly: report of two cases.

For diagnosing radiation optic neuropathy (RON) ophthalmological and imaging data were evaluated from 63 acromegalic patients, irradiated between 1967 and 1998. Two patients developed RON: one patient in one optic nerve 10 years and another patient in both optic nerves 5 months after radiation therapy. RON is a rare complication after external beam radiation therapy for acromegaly, which can occur after a considerable latency period.

Acromegaly↗
PubMed2002

The impact of central lung distance, maximal heart distance, and radiation technique on the volumetric dose of the lung and heart for intact breast radiation.

PURPOSE: To investigate the impact of radiographic parameter and radiation technique on the volumetric dose of lung and heart for intact breast radiation. METHODS AND MATERIALS: Forty patients with both two-dimensional (2D) and computed tomographic (CT) simulations were enrolled in the study. Central lung distance (CLD), maximal heart distance (MHD), and maximal heart length (MHL) were measured under virtual simulation. Four plans were compared for each patient. Plan A used a traditional 2D tangential setup. Plan B used clinical target volume (CTV) based three-dimensional (3D) planning. Both plans C and D used a combination of a medial breast field with shallow tangents. Plan D is a further modification of plan C. RESULTS: Under the traditional tangential setup, the mean ipsilateral lung dose and volume at 20, 30, and 40 Gy correlated linearly with CLD (R = 0.85 approximately 0.91). The mean ipsilateral lung dose (Gy) approximated 4 times the CLD value (cm), whereas the percentage volume (%) of ipsilateral lung at 20, 30, and 40 Gy was about 10 times the CLD (cm). The mean heart dose and percentage volume at 20, 30, and 40 Gy correlated with MHD (R = 0.76 approximately 0.80) and MHL (R = 0.65 approximately 0.75). The mean heart dose (Gy) approximated 3 times the MHD value (cm), and the percentage volume (%) of the heart at 10, 20, 30, and 40 Gy was about 6 times MHD (cm). Radiation technique impacted lung and heart dose. The 3D tangential plan (plan B) failed to reduce the volumetric dose of lung and heart from that of the 2D plan (plan A). The medial breast techniques (plans C and D) significantly decreased the volume of lung and heart receiving high doses (30 and 40 Gy). Plan D further decreased the 20 Gy volumes. By use of the medial breast technique, the lung and heart dose were not impacted by original CLD and MHD/MHL. Therefore, the improvement from the tangential technique was more remarkable for patients with CLD >or= 3.0 cm (p < 0.001). CONCLUSIONS: The CLD and MHD impact the volumetric dose of lung and heart. The application of 3D planning for tangential breast irradiation does not decrease heart and lung dose. Adding a medial breast port significantly decreases percentage volume (PV) of lung and heart receiving high doses, especially when the CLD is excessive.

Breast Neoplasms↗
PubMed1999

Comparison of three-dimensional conformal radiation therapy and intensity-modulated radiation therapy systems.

The use of three-dimensional conformal radiation therapy (3DCRT) has now become common practice in radiation oncology departments around the world. Using beam's eye viewing of volumes defined on a treatment planning computed tomography scan, beam directions and beam shapes can be selected to conform to the shape of the projected target and minimize dose to critical normal structures. Intensity-modulated radiation therapy (IMRT) can yield dose distributions that conform closely to the three-dimensional shape of the target volume while still minimizing dose to normal structures by allowing the beam intensity to vary across those shaped fields. Predicted dose distributions for patients with tumors of the prostate, nasopharynx, and paraspinal region are compared between plans made with 3DCRT programs and those with inverse-planned IMRT programs. The IMRT plans are calculated for either static or dynamic beam delivery methods using multileaf collimators. Results of these comparisons indicate that IMRT can yield significantly better dose distributions in some situations at the expense of additional time and resources. New technologies are being developed that should significantly reduce the time needed to plan, implement, and verify these treatments. Current research should help define the future role of IMRT in clinical practice.

Costs and Cost Analysis↗
PubMed2003

Radiation-induced genomic instability and its implications for radiation carcinogenesis.

Radiation-induced genomic instability is characterized by an increased rate of genetic alterations including cytogenetic rearrangements, mutations, gene amplifications, transformation and cell death in the progeny of irradiated cells multiple generations after the initial insult. Chromosomal rearrangements are the best-characterized end point of radiation-induced genomic instability, and many of the rearrangements described are similar to those found in human cancers. Chromosome breakage syndromes are defined by chromosome instability, and individuals with these diseases are cancer prone. Consequently, chromosomal instability as a phenotype may underlie some fraction of those changes leading to cancer. Here we attempt to relate current knowledge regarding radiation-induced chromosome instability with the emerging molecular information on the chromosome breakage syndromes. The goal is to understand how genetic and epigenetic factors might influence the onset of chromosome instability and the role of chromosomal instability in carcinogenesis.

Chromosome Breakage↗
PubMed1999

Molecular biology in radiation oncology. Radiation oncology perspective of BRCA1 and BRCA2.

The breast cancer susceptibility genes, BRCA1 and BRCA2, are used to illustrate the application of molecular biology to clinical radiation oncology. Identified by linkage analysis and cloned, the structure of the genes and the numerous mutations are determined by molecular biology techniques that examine the structure of the DNA and the proteins made by the normal and mutant alleles. Mutations in the non-transcribed portion of the gene will not be found in protein structure assays and may be important in gene function. In addition to potential deleterious mutations, normal polymorphisms of the gene will also be detected, therefore not all differences in gene sequence may represent important mutations, a finding that complicates genetic screening and counseling. The localization of the protein in the nucleus, the expression in relation to cell cycle and the association with RAD51 led to the discovery that the two BRCA genes may be involved in transcriptional regulation and DNA repair. The defect in DNA repair can increase radiosensitivity which might improve local control using breast-conserving treatment in a tumor which is homozygous for the loss of the gene (i.e., BRCA1 and BRCA2 are tumor suppressor genes). This is supported by the early reports of a high rate of local control with breast-conserving therapy. Nonetheless, this radiosensitivity theoretically may also lead to increased susceptibility to carcinogenic effects in surviving cells, a finding that might not be observed for decades. The susceptibility to radiation-induced DNA damage appears also to make the cells more sensitive to chemotherapy. Understanding the role of the normal BRCA genes in DNA repair might help define a novel mechanism for radiation sensitization by interfering with the normal gene function using a variety of molecular or biochemical therapies.

BRCA2 Protein↗
PubMed2002

Radiation-induced up-regulation of telomerase in KG1a cells is influenced by dose-rate and radiation quality.

PURPOSE: To examine the influence of dose, dose-rate and radiation quality on telomerase activity (TA) in the KG1a hematopoietic cell line. MATERIALS AND METHODS: KG1a cells were irradiated with gamma-rays (0.5-5 Gy) at 0.025 Gy/min, 0.30 Gy/min and 1.57 Gy/min and with a neutron/gamma-ray field (5 Gy). Cell viability was determined by trypan blue exclusion. Apoptosis and cell cycle distribution were evaluated by flow cytometry. Proliferative capacity was studied by MTS assay and TA by PCR. Following 3Gy gamma-irradiation, the expression of hTERT, hTR and TP1 genes was evaluated by RT-PCR. RESULTS: Dose- and dose-rate-dependent telomerase activation with an increase in hTERT mRNA and a drop in hTP1 mRNA were observed after irradiation. Down-regulation of telomerase activity occurred in a dose-dependent manner. Although non-significant changes in short-term survival were observed after irradiation, late apoptosis became evident after G2/M arrest. Early repression of TA preceded telomerase activation in samples irradiated with a neutron/gamma-ray field, in which short-term survival was affected. CONCLUSIONS: Radiation-induced telomerase activation depends on dose-rate. High-LET and low-LET irradiations induce similar changes in TA that differ mainly in their kinetics and their magnitude. Changes in TA are not related to cell-cycle redistribution nor to the induction of cell death; they are the consequence of specific regulatory responses to ionizing radiation. Mechanisms including both transcriptional and post-translational control may be involved in this regulation.

Apoptosis↗
PubMed2006

Radiation-induced molecular changes in rat mammary tissue: possible implications for radiation-induced carcinogenesis.

PURPOSE: Ionizing radiation is a potent mammary gland carcinogen, yet the exact molecular etiology of radiation-induced breast cancer remains unknown. MATERIALS AND METHODS: Our study utilized a rat model of breast carcinogenesis to analyse the molecular and epigenetic changes induced in mammary gland tissue upon exposure to ionizing radiation (IR). Using a methylation-sensitive cytosine extension assay we studied the IR-induced changes in DNA methylation. In parallel, we analysed the expression of proteins involved in DNA methylation, DNA repair and cell proliferation control. Molecular changes were related to cellular proliferation and apoptosis. RESULTS: We found that IR led to a loss of genomic cytosine methylation in the exposed mammary tissue. Global DNA hypomethylation was paralleled by reduction in the levels of maintenance (DNMT1) and de novo (DNMT3a and 3b) DNA methyltransferases and methyl-binding protein MeCP2. The observed DNA hypomethylation was linked, at least in part, to activation of DNA repair processes. Concurrently, we observed increased levels of phosphorylated extracellular signal-regulated kinase (p-ERK1/2), phosphorylated AKT kinase (p-AKT), cyclin D1 and proliferating cells nuclear antigen (PCNA) proteins, suggesting IR alters intra-cellular signaling and cell cycle control mechanisms in mammary tissue. We also noted a significant induction of apoptosis in the exposed tissue 6 hours after irradiation. The observed apoptosis levels were paralleled by the slight elevation of cellular proliferation. CONCLUSIONS: We have demonstrated that a single exposure to 5 Gy of X rays leads to noticeable epigenetic changes in the rat mammary gland that occurred in the context of activation of DNA damage repair and alterations in the pro-survival growth-stimulatory cellular signaling pathways. The possible cellular repercussions of the observed changes in relationship to breast carcinogenesis are discussed.

Animals↗
PubMed1981

Effect of low dose ionizing radiation on the murine pericryptal fibroblast sheath: radiation damage in a mesenchymal system in vivo.

The effect of low dose ionizing radiation from a variety of sources on the murine small intestinal and colonic pericryptal fibroblast sheath (PCFS) has been investigated. Ultrastructural and light microscopic changes seen within 3 hours after radiation resembles the mode of cell death known as apoptosis. The apoptotic index (AI) was shown to rise steadily for 4 hours after irradiation, and then to return to control levels by 10 hours. 137Cs gamma-irradiation over a range of doses from 0-803 cGy caused an increase in AI from control values of 1-2 per cent to a plateau level of approximately 8.5 per cent for doses above 40 cGy. Investigation of the response of the PCFS to doses of 137Cs and 60Co gamma-irradiation and X-irradiation below 40 cGy demonstrated a steady increase with dose in AI. The survival curve for the radiosensitive subpopulation susceptible to death through apoptosis as a consequence of exposure to non-acute doses of radiation has a D0 of 10.6 cGy and an extrapolation number of 2.3.

Animals↗
PubMed1980

Free radical initiation in proteins and amino acids by ionizing and ultraviolet radiations and lipid oxidation--Part I: ionizing radiation.

Parallels and similarities in chemical and functional damage to proteins by ionizing and UV radiations and oxidizing lipids have been recognized for some time. However, only recently have oxidizing lipids been shown directly by electron spin resonance to be radiomimetic also in their capacity for protein free radical production. Free radicals play a key role in the transformation of energy to molecular and cellular damage. It is thus of critical importance to elucidate the general mechanisms of free radical formation and reactions in proteins in order to understand protein involvement in various pathological conditions and in food deterioration. Accordingly, this review is a detailed comparison of gamma radiation, UV radiation, and lipid oxidation for what is presently known concerning (1) the specific modes of energy deposition and free radical formation, (2) the free radicals formed in proteins and amino acids, and (3) the typical damage correlating with these radicals.

Amino Acids↗
PubMed1965

Effects of arginine deprivation, ultraviolet radiation, and x-radiation on cultured KB cells. A cytochemical and ultrastructural study.

CULTURED KB CELLS (DERIVED FROM A HUMAN ORAL CARCINOMA) GROWN IN MONOLAYERS WERE INJURED BY ONE OF THREE AGENTS: starvation by arginine deprivation or treatment with high doses of either ultraviolet radiation or x-radiation. The different agents produced changes in nucleolar structure and varying accumulations of triglyceride and glycogen. All three agents produced an increase in number and size of lysosomes. These were studied in acid phosphatase preparations, viewed by both light and electron microscopy, and, occasionally, in vital dye, esterase, and aryl sulfatase preparations. Ultrastructurally, alterations in lysosomes suggested that "residual bodies" developed in a variety of ways, i.e., from the endoplasmic reticulum, multivesicular bodies, or autophagic vacuoles. Following all three agents the endoplasmic reticulum assumed the form of "rough" or "smooth" whorls, and, after two of the agents, arginine deprivation or ultraviolet radiation, it acquired cytochemically demonstrable acid phosphatase activity. Near connections between the endoplasmic reticulum and lysosomes raise the possibility that in KB cells, at least when injured, the endoplasmic reticulum is involved in the formation of lysosomes and the transport of acid phosphatase to them.

Acid Phosphatase↗
PubMed1981

The influence of ultraviolet radiation on allergic contact dermatitis in the guinea-pig. I. UVB radiation.

Guniea-pigs were sensitized by percutaneous application of dinitrochlorobenzene and exposed to UVB (280-320 nm) radiation. The exposure to radiation diminished the response to an elicitation dose of the hapten administered 14 days later within the site of irradiation. The exposure dose of radiation required to produce this effect resulted in a marked erythemal response, but this response did not conceal the contact allergic reaction. The site of elicitation of the allergic response had to be included in the exposure field.

Animals↗