Base de dados : MEDLINE
Pesquisa : E02.815.635.700.700 [Categoria DeCS]
Referências encontradas : 7425 [refinar]
Mostrando: 1 .. 10   no formato [Longo]

página 1 de 743 ir para página                         

  1 / 7425 MEDLINE  
              next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:29505510
Autor:Chen XR; Dong JN; Zhang F; Yao TL
Endereço:Department of Ultrasound, The Second Affiliated Hospital of Mudanjiang Medical University.
Título:Efficacy and safety of image-guidance radiotherapy by helical tomotherapy in patients with lung cancer.
Fonte:Medicine (Baltimore); 97(1):e9243, 2018 Jan.
ISSN:1536-5964
País de publicação:United States
Idioma:eng
Resumo:This study aimed to explore the efficacy and toxicity of image-guided stereotactic body radiotherapy (IGSBR) by helical tomotherapy in patients with lung cancer among Chinese Han population.A total of 21 patients with stage I lung cancer were included. They received a total of 60 Gy factions IGSBR. The outcomes included complete response (CR), partial response (PR), stable disease (SD), progress disease (PD), overall response rate (ORR), and overall survival (OS). In addition, toxicities were also recorded in this study.Three-year CR, PR, SD, PD, ORR, and OS were 47.6%, 38.1%, 9.5%, 4.8%, 85.7%, and 48.0 months, respectively. Additionally, mild toxicities were found in this study.This study demonstrated that IGSBR is efficacious for patients with stage I lung cancer with mild toxicities among Chinese Han population.
Tipo de publicação: JOURNAL ARTICLE


  2 / 7425 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28741600
Autor:Mescher H; Ulrich S; Bangert M
Endereço:Department of Medical Physics in Radiation Oncology, German Cancer Research Center-DKFZ, Im NeuenheimerFeld 280, D-69120 Heidelberg, Germany. Heidelberg Institute for Radiation Oncology-HIRO, Im Neuenheimer Feld 280, D-69120, Germany.
Título:Coverage-based constraints for IMRT optimization.
Fonte:Phys Med Biol; 62(18):N460-N473, 2017 Sep 05.
ISSN:1361-6560
País de publicação:England
Idioma:eng
Resumo:Radiation therapy treatment planning requires an incorporation of uncertainties in order to guarantee an adequate irradiation of the tumor volumes. In current clinical practice, uncertainties are accounted for implicitly with an expansion of the target volume according to generic margin recipes. Alternatively, it is possible to account for uncertainties by explicit minimization of objectives that describe worst-case treatment scenarios, the expectation value of the treatment or the coverage probability of the target volumes during treatment planning. In this note we show that approaches relying on objectives to induce a specific coverage of the clinical target volumes are inevitably sensitive to variation of the relative weighting of the objectives. To address this issue, we introduce coverage-based constraints for intensity-modulated radiation therapy (IMRT) treatment planning. Our implementation follows the concept of coverage-optimized planning that considers explicit error scenarios to calculate and optimize patient-specific probabilities [Formula: see text] of covering a specific target volume fraction [Formula: see text] with a certain dose [Formula: see text]. Using a constraint-based reformulation of coverage-based objectives we eliminate the trade-off between coverage and competing objectives during treatment planning. In-depth convergence tests including 324 treatment plan optimizations demonstrate the reliability of coverage-based constraints for varying levels of probability, dose and volume. General clinical applicability of coverage-based constraints is demonstrated for two cases. A sensitivity analysis regarding penalty variations within this planing study based on IMRT treatment planning using (1) coverage-based constraints, (2) coverage-based objectives, (3) probabilistic optimization, (4) robust optimization and (5) conventional margins illustrates the potential benefit of coverage-based constraints that do not require tedious adjustment of target volume objectives.
Tipo de publicação: JOURNAL ARTICLE


  3 / 7425 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28463164
Autor:Penninkhof J; Spadola S; Breedveld S; Baaijens M; Lanconelli N; Heijmen B
Endereço:Department of Radiation Oncology, Erasmus M.C. Cancer Institute, Rotterdam, The Netherlands. Electronic address: j.penninkhof@erasmusmc.nl.
Título:Individualized Selection of Beam Angles and Treatment Isocenter in Tangential Breast Intensity Modulated Radiation Therapy.
Fonte:Int J Radiat Oncol Biol Phys; 98(2):447-453, 2017 06 01.
ISSN:1879-355X
País de publicação:United States
Idioma:eng
Resumo:PURPOSE AND OBJECTIVE: Propose a novel method for individualized selection of beam angles and treatment isocenter in tangential breast intensity modulated radiation therapy (IMRT). METHODS AND MATERIALS: For each patient, beam and isocenter selection starts with the fully automatic generation of a large database of IMRT plans (up to 847 in this study); each of these plans belongs to a unique combination of isocenter position, lateral beam angle, and medial beam angle. The imposed hard planning constraint on patient maximum dose may result in plans with unacceptable target dose delivery. Such plans are excluded from further analyses. Owing to differences in beam setup, database plans differ in mean doses to organs at risk (OARs). These mean doses are used to construct 2-dimensional graphs, showing relationships between: (1) contralateral breast dose and ipsilateral lung dose; and (2) contralateral breast dose and heart dose (analyzed only for left-sided). The graphs can be used for selection of the isocenter and beam angles with the optimal, patient-specific tradeoffs between the mean OAR doses. For 30 previously treated patients (15 left-sided and 15 right-sided tumors), graphs were generated considering only the clinically applied isocenter with 121 tangential beam angle pairs. For 20 of the 30 patients, 6 alternative isocenters were also investigated. RESULTS: Computation time for automatic generation of 121 IMRT plans took on average 30 minutes. The generated graphs demonstrated large variations in tradeoffs between conflicting OAR objectives, depending on beam angles and patient anatomy. For patients with isocenter optimization, 847 IMRT plans were considered. Adding isocenter position optimization next to beam angle optimization had a small impact on the final plan quality. CONCLUSION: A method is proposed for individualized selection of beam angles in tangential breast IMRT. This may be especially important for patients with cardiac risk factors or an enhanced risk for the development of contralateral breast cancer.
Tipo de publicação: JOURNAL ARTICLE


  4 / 7425 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28463160
Autor:Olsen JR; Moughan J; Myerson R; Abitbol A; Doncals DE; Johnson D; Schefter TE; Chen Y; Fisher B; Michalski J; Narayan S; Chang A; Crane CH; Kachnic L
Endereço:University of Colorado Denver, Aurora, Colorado. Electronic address: Jeffrey.R.Olsen@ucdenver.edu.
Título:Predictors of Radiation Therapy-Related Gastrointestinal Toxicity From Anal Cancer Dose-Painted Intensity Modulated Radiation Therapy: Secondary Analysis of NRG Oncology RTOG 0529.
Fonte:Int J Radiat Oncol Biol Phys; 98(2):400-408, 2017 06 01.
ISSN:1879-355X
País de publicação:United States
Idioma:eng
Resumo:PURPOSE: NRG Oncology RTOG 0529 assessed the feasibility of dose-painted intensity modulated radiation therapy (DP-IMRT) to reduce the acute morbidity of chemoradiation with 5-fluorouracil (5FU) and mitomycin-C (MMC) for T2-4N0-3M0 anal cancer. This secondary analysis was performed to identify patient and treatment factors associated with acute and late gastrointestinal (GI) adverse events (AEs). METHODS AND MATERIALS: NRG Oncology RTOG 0529 treatment plans were reviewed to extract dose-volume data for tightly contoured small bowel, loosely contoured anterior pelvic contents (APC), and uninvolved colon outside the target volume (UC). Univariate logistic regression was performed to evaluate association between volumes of each structure receiving doses ≥5 to 60 Gy (V5-V60) in 5-Gy increments between patients with and without grade ≥2 acute and late GI AEs, and grade ≥3 acute GI AEs. Additional patient and treatment factors were evaluated in multivariate logistic regression (acute AEs) or Cox proportional hazards models (late AEs). RESULTS: Among 52 evaluable patients, grade ≥2 acute, grade ≥2 late, and grade ≥3 acute GI AEs were observed in 35, 17, and 10 patients, respectively. Trends (P<.05) toward statistically significant associations were observed between grade ≥2 acute GI AEs and small bowel dose (V20-V40), grade ≥2 late GI AEs and APC dose (V60), grade ≥3 acute GI AEs and APC dose (V5-V25), increasing age, tumor size >4 cm, and worse Zubrod performance status. Small bowel volumes of 186.0 cc, 155.0 cc, 41.0 cc, and 30.4 cc receiving doses greater than 25, 30, 35, and 40 Gy, respectively, correlated with increased risk of acute grade ≥2 GI AEs. CONCLUSIONS: Acute and late GI AEs from 5FU/MMC chemoradiation using DP-IMRT correlate with radiation dose to the small bowel and APC. Such associations will be incorporated in the dose-volume normal tissue constraint design for future NRG oncology anal cancer studies.
Tipo de publicação: JOURNAL ARTICLE; RESEARCH SUPPORT, N.I.H., EXTRAMURAL
Nome de substância:0 (Antineoplastic Agents); 50SG953SK6 (Mitomycin); U3P01618RT (Fluorouracil)


  5 / 7425 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28463155
Autor:Nanda RH; Ganju RG; Schreibmann E; Chen Z; Zhang C; Jegadeesh N; Cassidy R; Deng C; Eaton BR; Esiashvili N
Endereço:Department of Radiation Oncology, Winship Cancer Institute, Emory University College of Medicine, Atlanta, Georgia. Electronic address: rhazari@emory.edu.
Título:Correlation of Acute and Late Brainstem Toxicities With Dose-Volume Data for Pediatric Patients With Posterior Fossa Malignancies.
Fonte:Int J Radiat Oncol Biol Phys; 98(2):360-366, 2017 06 01.
ISSN:1879-355X
País de publicação:United States
Idioma:eng
Resumo:PURPOSE: Radiation-induced brainstem toxicity after treatment of pediatric posterior fossa malignancies is incompletely understood, especially in the era of intensity modulated radiation therapy (IMRT). The rates of, and predictive factors for, brainstem toxicity after photon RT for posterior fossa tumors were examined. METHODS AND MATERIALS: After institutional review board approval, 60 pediatric patients treated at our institution for nonmetastatic infratentorial ependymoma and medulloblastoma with IMRT were included in the present analysis. Dosimetric variables, including the mean and maximum dose to the brainstem, the dose to 10% to 90% of the brainstem (in 10% increments), and the volume of the brainstem receiving 40, 45, 50, and 55 Gy were recorded for each patient. Acute (onset within 3 months) and late (>3 months of RT completion) RT-induced brainstem toxicities with clinical and radiographic correlates were scored using Common Terminology Criteria for Adverse Events, version 4.0. RESULTS: Patients aged 1.4 to 21.8 years underwent IMRT or volumetric arc therapy postoperatively to the posterior fossa or tumor bed. At a median clinical follow-up period of 2.8 years, 14 patients had developed symptomatic brainstem toxicity (crude incidence 23.3%). No correlation was found between the dosimetric variables examined and brainstem toxicity. Vascular injury or ischemia showed a strong trend toward predicting brainstem toxicity (P=.054). Patients with grade 3 to 5 brainstem toxicity had undergone treatment to significant volumes of the posterior fossa. CONCLUSION: The results of the present series demonstrate a low, but not negligible, risk of brainstem radiation necrosis for pediatric patients with posterior fossa malignancies treated with IMRT. No specific dose-volume correlations were identified; however, modern treatment volumes might help limit the incidence of severe toxicity. Additional work investigating inherent biologic sensitivity might also provide further insight into this clinical problem.
Tipo de publicação: JOURNAL ARTICLE


  6 / 7425 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
Texto completo
PMID:29360138
Autor:Lawrie TA; Green JT; Beresford M; Wedlake L; Burden S; Davidson SE; Lal S; Henson CC; Andreyev HJN
Endereço:Cochrane Gynaecological, Neuro-oncology and Orphan Cancer Group, 1st Floor Education Centre, Royal United Hospital, Combe Park, Bath, UK, BA1 3NG.
Título:Interventions to reduce acute and late adverse gastrointestinal effects of pelvic radiotherapy for primary pelvic cancers.
Fonte:Cochrane Database Syst Rev; 1:CD012529, 2018 Jan 23.
ISSN:1469-493X
País de publicação:England
Idioma:eng
Resumo:BACKGROUND: An increasing number of people survive cancer but a significant proportion have gastrointestinal side effects as a result of radiotherapy (RT), which impairs their quality of life (QoL). OBJECTIVES: To determine which prophylactic interventions reduce the incidence, severity or both of adverse gastrointestinal effects among adults receiving radiotherapy to treat primary pelvic cancers. SEARCH METHODS: We conducted searches of CENTRAL, MEDLINE, and Embase in September 2016 and updated them on 2 November 2017. We also searched clinical trial registries. SELECTION CRITERIA: We included randomised controlled trials (RCTs) of interventions to prevent adverse gastrointestinal effects of pelvic radiotherapy among adults receiving radiotherapy to treat primary pelvic cancers, including radiotherapy techniques, other aspects of radiotherapy delivery, pharmacological interventions and non-pharmacological interventions. Studies needed a sample size of 20 or more participants and needed to evaluate gastrointestinal toxicity outcomes. We excluded studies that evaluated dosimetric parameters only. We also excluded trials of interventions to treat acute gastrointestinal symptoms, trials of altered fractionation and dose escalation schedules, and trials of pre- versus postoperative radiotherapy regimens, to restrict the vast scope of the review. DATA COLLECTION AND ANALYSIS: We used standard Cochrane methodology. We used the random-effects statistical model for all meta-analyses, and the GRADE system to rate the certainty of the evidence. MAIN RESULTS: We included 92 RCTs involving more than 10,000 men and women undergoing pelvic radiotherapy. Trials involved 44 different interventions, including radiotherapy techniques (11 trials, 4 interventions/comparisons), other aspects of radiotherapy delivery (14 trials, 10 interventions), pharmacological interventions (38 trials, 16 interventions), and non-pharmacological interventions (29 trials, 13 interventions). Most studies (79/92) had design limitations. Thirteen studies had a low risk of bias, 50 studies had an unclear risk of bias and 29 studies had a high risk of bias. Main findings include the following:Radiotherapy techniques: Intensity-modulated radiotherapy (IMRT) versus 3D conformal RT (3DCRT) may reduce acute (risk ratio (RR) 0.48, 95% confidence interval (CI) 0.26 to 0.88; participants = 444; studies = 4; I = 77%; low-certainty evidence) and late gastrointestinal (GI) toxicity grade 2+ (RR 0.37, 95% CI 0.21 to 0.65; participants = 332; studies = 2; I = 0%; low-certainty evidence). Conformal RT (3DCRT or IMRT) versus conventional RT reduces acute GI toxicity grade 2+ (RR 0.57, 95% CI 0.40 to 0.82; participants = 307; studies = 2; I = 0%; high-certainty evidence) and probably leads to less late GI toxicity grade 2+ (RR 0.49, 95% CI 0.22 to 1.09; participants = 517; studies = 3; I = 44%; moderate-certainty evidence). When brachytherapy (BT) is used instead of external beam radiotherapy (EBRT) in early endometrial cancer, evidence indicates that it reduces acute GI toxicity (grade 2+) (RR 0.02, 95% CI 0.00 to 0.18; participants = 423; studies = 1; high-certainty evidence).Other aspects of radiotherapy delivery: There is probably little or no difference in acute GI toxicity grade 2+ with reduced radiation dose volume (RR 1.21, 95% CI 0.81 to 1.81; participants = 211; studies = 1; moderate-certainty evidence) and maybe no difference in late GI toxicity grade 2+ (RR 1.02, 95% CI 0.15 to 6.97; participants = 107; studies = 1; low-certainty evidence). Evening delivery of RT may reduce acute GI toxicity (diarrhoea) grade 2+ during RT compared with morning delivery of RT (RR 0.51, 95% CI 0.34 to 0.76; participants = 294; studies = 2; I = 0%; low-certainty evidence). There may be no difference in acute (RR 2.22, 95% CI 0.62 to 7.93, participants = 110; studies = 1) and late GI toxicity grade 2+ (RR 0.44, 95% CI 0.12 to 1.65; participants = 81; studies = 1) between a bladder volume preparation of 1080 mls and that of 540 mls (low-certainty evidence). Low-certainty evidence on balloon and hydrogel spacers suggests that these interventions for prostate cancer RT may make little or no difference to GI outcomes.Pharmacological interventions: Evidence for any beneficial effects of aminosalicylates, sucralfate, amifostine, corticosteroid enemas, bile acid sequestrants, famotidine and selenium is of a low or very low certainty. However, evidence on certain aminosalicylates (mesalazine, olsalazine), misoprostol suppositories, oral magnesium oxide and octreotide injections suggests that these agents may worsen GI symptoms, such as diarrhoea or rectal bleeding.Non-pharmacological interventions: Low-certainty evidence suggests that protein supplements (RR 0.23, 95% CI 0.07 to 0.74; participants = 74; studies = 1), dietary counselling (RR 0.04, 95% CI 0.00 to 0.60; participants = 74; studies = 1) and probiotics (RR 0.43, 95% CI 0.22 to 0.82; participants = 923; studies = 5; I = 91%) may reduce acute RT-related diarrhoea (grade 2+). Dietary counselling may also reduce diarrhoeal symptoms in the long term (at five years, RR 0.05, 95% CI 0.00 to 0.78; participants = 61; studies = 1). Low-certainty evidence from one study (108 participants) suggests that a high-fibre diet may have a beneficial effect on GI symptoms (mean difference (MD) 6.10, 95% CI 1.71 to 10.49) and quality of life (MD 20.50, 95% CI 9.97 to 31.03) at one year. High-certainty evidence indicates that glutamine supplements do not prevent RT-induced diarrhoea. Evidence on various other non-pharmacological interventions, such as green tea tablets, is lacking.Quality of life was rarely and inconsistently reported across included studies, and the available data were seldom adequate for meta-analysis. AUTHORS' CONCLUSIONS: Conformal radiotherapy techniques are an improvement on older radiotherapy techniques. IMRT may be better than 3DCRT in terms of GI toxicity, but the evidence to support this is uncertain. There is no high-quality evidence to support the use of any other prophylactic intervention evaluated. However, evidence on some potential interventions shows that they probably have no role to play in reducing RT-related GI toxicity. More RCTs are needed for interventions with limited evidence suggesting potential benefits.
Tipo de publicação: JOURNAL ARTICLE; META-ANALYSIS; REVIEW
Nome de substância:0 (Gastrointestinal Agents)


  7 / 7425 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:29182384
Autor:King RB; Osman SO; Fairmichael C; Irvine DM; Lyons CA; Ravi A; O'Sullivan JM; Hounsell AR; Mitchell DM; McGarry CK; Jain S
Endereço:1 Centre for Cancer Research and Cell Biology, Queen's University Belfast , Belfast , Ireland.
Título:Efficacy of a rectal spacer with prostate SABR-first UK experience.
Fonte:Br J Radiol; 91(1083):20170672, 2018 Feb.
ISSN:1748-880X
País de publicação:England
Idioma:eng
Resumo:OBJECTIVE: This study assessed the use of implanted hydrogel rectal spacers for stereotactic ablative radiotherapy-volumetric modulated arc therapy (SABR-VMAT) patients, investigating practicality, dosimetric impact, normal tissue complication probability (NTCP) and early toxicity. METHODS: Data from the first 6 patients treated within a prostate SABR and rectal spacer trial were examined to determine spacer insertion tolerability, resultant changes in treatment planning and dosimetry and early toxicity effects. CT scans acquired prior to spacer insertion were used to generate SABR plans which were compared to post-insertion plans. Plans were evaluated for target coverage, conformity, and organs at risk doses with NTCPs also determined from resultant dose fluences. Early toxicity data were also collected. RESULTS: All patients had successful spacer insertion under local anaesthetic with maximal Grade 1 toxicity. All plans were highly conformal, with no significant differences in clinical target volume dose coverage between pre- and post-spacer plans. Substantial improvements in rectal dose metrics were observed in post-spacer plans, e.g. rectal volume receiving 36 Gy reduced by ≥42% for all patients. Median NTCP for Grade 2 + rectal bleeding significantly decreased from 4.9 to 0.8% with the use of a rectal spacer (p = 0.031). To date, two episodes of acute Grade 1 proctitis have been reported following treatment. CONCLUSION: The spacer resulted in clinically and statistically significant reduction in rectal doses for all patients. Advances in knowledge: This is one of the first studies to investigate the efficacy of a hydrogel spacer in prostate SABR treatments. Observed dose sparing of the rectum is predicted to result in meaningful clinical benefit.
Tipo de publicação: JOURNAL ARTICLE
Nome de substância:25852-47-5 (Hydrogel, Polyethylene Glycol Dimethacrylate)


  8 / 7425 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28449713
Autor:Liu X; Huang E; Wang Y; He Y; Luo H; Zhong M; Qiu D; Li C; Yang H; He G; Zhou J; Jin F
Endereço:Department of Radiation Oncology, Chongqing Cancer Institute & Hospital & Cancer Center, Shapingba District, Chongqing, 400030, China.
Título:Dosimetric comparison of helical tomotherapy, VMAT, fixed-field IMRT and 3D-conformal radiotherapy for stage I-II nasal natural killer T-cell lymphoma.
Fonte:Radiat Oncol; 12(1):76, 2017 Apr 27.
ISSN:1748-717X
País de publicação:England
Idioma:eng
Resumo:BACKGROUND: The aim of this study was to compare radiotherapy plans for Stage I-II nasal natural killer/T-cell lymphoma (NNKTL) using helical tomotherapy (HT), volumetric-modulated arc therapy (VMAT), Fixed-Field intensity-modulated radiotherapy (IMRT), and three-dimensional conformal radiotherapy (3D-CRT). METHODS: Eight patents with Stage I-II NNKTL treated with IMRT were re-planned for HT, VMAT (two full arcs), and 3D-CRT. The quality of target coverage, the exposure of normal tissue and the efficiency of radiation delivery were analyzed. RESULTS: HT showed significant improvement over IMRT in terms of D , cold spot volume and homogeneity index (HI) of planning target volume (PTV). VMAT provided best dose uniformity (p = 0.000) to PTV, while HT had best dose homogeneity among the four radiotherapy techniques (p = 0.000) to PTV. VMAT obviously reduced treatment time (p = 0.010; 0.000) compared to HT and IMRT. Mean dose of left and right optic nerve was significantly reduced by IMRT compared to HT (19.86%, p = 0.000; 21.40%, p = 0.002) and VMAT (8.97%, p = 0.002; 9.35%, p = 0.001), and maximum dose of left lens of VMAT increased over the HT (36.25%, p = 0.043) and IMRT (40.65%, p = 0.001). CONCLUSION: The unexpected results show that both HT and VMAT can achieve higher conformal treatment plans while getting worse organs at risk (OARs) sparing than IMRT for patients with Stage I-II NNKTL. VMAT requires the shortest delivery time, and IMRT delivers the lowest dose to most OARs. The results could provide guidance for selecting proper radiation technologies for different cases.
Tipo de publicação: COMPARATIVE STUDY; JOURNAL ARTICLE


  9 / 7425 MEDLINE  
              first record previous record next record last record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28449704
Autor:Fogliata A; Reggiori G; Stravato A; Lobefalo F; Franzese C; Franceschini D; Tomatis S; Mancosu P; Scorsetti M; Cozzi L
Endereço:Humanitas Research Hospital and Cancer Center, Radiotherapy and Radiosurgery Department, Milan, Rozzano, Italy. Antonella.Fogliata@humanitas.it.
Título:RapidPlan head and neck model: the objectives and possible clinical benefit.
Fonte:Radiat Oncol; 12(1):73, 2017 Apr 27.
ISSN:1748-717X
País de publicação:England
Idioma:eng
Resumo:BACKGROUND: To evaluate a knowledge based planning model for RapidPlan (RP) generated for advanced head and neck cancer (HNC) patient treatments, as well its ability to possibly improve the clinical plan quality. The stability of the model was assessed also for a different beam geometry, different dose fractionation and different management of bilateral structures (parotids). METHODS: Dosimetric and geometric data from plans of 83 patients presenting HNC were selected for the model training. All the plans used volumetric modulated arc therapy (VMAT, RapidArc) to treat two targets at dose levels of 69.96 and 54.45 Gy in 33 fractions with simultaneous integrated boost. Two models were generated, the first separating the ipsi- and contra-lateral parotids, while the second associating the two parotids to a single structure for training. The optimization objectives were adjusted to the final model to better translate the institutional planning and dosimetric strategies and trade-offs. The models were validated on 20 HNC patients, comparing the RP generated plans and the clinical plans. RP generated plans were also compared between the clinical beam arrangement and a simpler geometry, as well as for a different fractionation scheme. RESULTS: RP improved significantly the clinical plan quality, with a reduction of 2 Gy, 5 Gy, and 10 Gy of the mean parotid, oral cavity and laryngeal doses, respectively. A simpler beam geometry was deteriorating the plan quality, but in a small amount, keeping a significant improvement relative to the clinical plan. The two models, with one or two parotid structures, showed very similar results. NTCP evaluations indicated the possibility of improving (NTCP decreasing of about 7%) the toxicity profile when using the RP solution. CONCLUSIONS: The HNC RP model showed improved plan quality and planning stability for beam geometry and fractionation. An adequate choice of the objectives in the model is necessary for the trade-offs strategies.
Tipo de publicação: JOURNAL ARTICLE


  10 / 7425 MEDLINE  
              first record previous record
seleciona
para imprimir
Fotocópia
Texto completo
PMID:28449708
Autor:Schneider U; Ernst M; Hartmann M
Endereço:Department of Physics, Science Faculty, University of Zürich, Zürich, Switzerland. uwe.schneider@uzh.ch.
Título:The dose-response relationship for cardiovascular disease is not necessarily linear.
Fonte:Radiat Oncol; 12(1):74, 2017 Apr 27.
ISSN:1748-717X
País de publicação:England
Idioma:eng
Resumo:The probability for a complication after radiotherapy is usually a function of dose and volume in the organ or tissue of interest. In most epidemiological studies the risk for a complication is stratified in terms of dose, but not irradiated volume. We show that the obtained risk cannot generally be applied to radiotherapy patients.The epidemiological data of Darby et al. (N Engl J Med 368:2527, 2013) who found a linear relationship between the excess relative risk of major coronary events as function of mean heart dose in patients treated with tangential breast irradiation are analyzed. We have used the relative seriality model for a partly irradiated heart ("a lot to a little") which models radiation therapy using two tangential fields. The relative seriality model was then used to predict NTCP of cardiovascular disease for a homogenously irradiated heart ("a little to a lot"). The relative seriality model was fitted to the data of Darby et al. (N Engl J Med 368:2527, 2013) for tangential breast irradiation. For the situation "a little to a lot" it was found that the dose-response relationship is sigmoidal and contradicts the findings of Darby et al. (N Engl J Med 368:2527, 2013). It was shown in this work that epidemiological studies which predict a linear dose-response relationship for cardiovascular disease can be reproduced by bio-physical models for normal tissue complication. For irradiation situations which were not included in the epidemiological studies, e.g. a homogenous irradiation of the heart ("a little to a lot") the dose-response curve can be different. This could have consequences whether or not IMRT should be used for treating breast cancer. We believe that the results of epidemiological studies should not be generally used to predict normal tissue complications. It is better to use such data to optimize bio-physical models which can then be applied (with caution) to general treatment situations.
Tipo de publicação: LETTER



página 1 de 743 ir para página                         
   


Refinar a pesquisa
  Base de dados : MEDLINE Formulário avançado   

    Pesquisar no campo  
1  
2
3
 
           



Search engine: iAH v2.6 powered by WWWISIS

BIREME/OPAS/OMS - Centro Latino-Americano e do Caribe de Informação em Ciências da Saúde