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Prescribed Dose (prescribed + dose)
Selected AbstractsDefinitive radiotherapy in the management of chemodectomas arising in the temporal bone, carotid body, and glomus vagaleHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 5 2001Russell W. Hinerman MD Abstract Purpose To evaluate the results of treatment for 71 patients with 80 chemodectomas of the temporal bone, carotid body, or glomus vagale who were treated with radiation therapy (RT) alone (72 tumors in 71 patients) or subtotal resection and RT (8 tumors) at the University of Florida between 1968 and 1998. Methods and Materials Sixty-six lesions were previously untreated, whereas 14 had undergone prior treatment (surgery, 11 lesions; RT, 1 lesion; or both, 2 lesions) and were treated for locally recurrent disease. All three patients who received prior RT had been treated at other institutions. Patients had minimum follow-up times as follows: 2 years, 66 patients (93%); 5 years, 53 patients (75%); 10 years, 37 patients (52%); 15 years, 29 patients (41%); 20 years, 18 patients (25%); 25 years, 12 patients (17%); and 30 years, 4 patients (6%). Results There were five local recurrences at 2.6 years, 4.6 years, 5.3 years, 8.3 years, and 18.8 years, respectively. Four were in glomus jugulare tumors and one was a carotid body tumor. Two of the four patients with glomus jugulare failures were salvaged, one with stereotactic radiosurgery and one with surgery and postoperative RT at another institution. Two of the five recurrences had been treated previously at other institutions with RT and/or surgery. Treatment for a third recurrence was discontinued, against medical advice, before receiving the prescribed dose. There were, therefore, only 2 failures in 65 previously untreated lesions receiving the prescribed course of RT. The overall crude local control rate for all 80 lesions was 94%, with an ultimate local control rate of 96% after salvage treatment. The incidence of treatment-related complications was low. Conclusions Irradiation offers a high probability of tumor control with relatively minimal risks for patients with chemodectomas of the temporal bone and neck. There were no severe treatment complications. © 2001 John Wiley & Sons, Inc. Head Neck 23: 363,371, 2001. [source] Intensity-modulated radiotherapy with an integrated boost to the macroscopic tumor volume in the treatment of high-grade gliomasINTERNATIONAL JOURNAL OF CANCER, Issue 6 2001Christoph Thilmann M.D. Abstract Integrated boost radiotherapy (IBRT) delivers a higher fraction size to the gross tumor volume and a conventional fraction size to the surrounding tissue of microscopic spread. We compared stereotactic conformal radiotherapy (SCRT) and intensity-modulated radiotherapy (IMRT) with regard to their suitability for IBRT in the treatment of high-grade gliomas. In 20 patients treated with conventional radiotherapy, an additional treatment plan for IBRT [planning target volume (PTV1) defined as contrast-enhancing lesion plus margin due to setup errors 75 Gy, PTV2 defined as edema plus margin due to microscopic spread and setup error 60 Gy] with 7 non-coplanar beams for IMRT and for SCRT was carried out and compared. The part of the PTV2 irradiated with more than 107% of the prescribed dose was 13.9% for IMRT and 30.9% for SCRT (P < 0.001). Dose coverage of PTV2 (volume above 95% of the prescribed dose) was improved with IMRT (88.4% vs. 75.3% with SCRT, P < 0.001). Dose coverage of PTV1 was slightly higher with SCRT (93.7% vs. 87.5% with IMRT), but the conformity to the boost shape was improved by IMRT [conformity index (COIN95) = 0.85 vs. 0.69 with SCRT]. Simultaneously the brain volume irradiated with > 50 Gy was reduced from 60 to 33 cc (P < 0.001). We conclude that IMRT is suitable for local dose escalation in the enhancing lesion and for delivering a homogeneous dose to the PTV2 outside the PTV1 at the same time. Our encouraging results justify application of IMRT for IBRT in the treatment of high-grade gliomas. For clinical evaluation a phase III study has been initiated. © 2001 Wiley-Liss, Inc. [source] Comparison of intensity modulated radiation therapy (IMRT) treatment techniques for nasopharyngeal carcinomaINTERNATIONAL JOURNAL OF CANCER, Issue 2 2001Jason Chia-Hsien Cheng M.D. Abstract We studied target volume coverage and normal tissue sparing of serial tomotherapy intensity modulated radiation therapy (IMRT) and fixed-field IMRT for nasopharyngeal carcinoma (NPC), as compared with those of conventional beam arrangements. Twelve patients with NPC (T2-4N1-3M0) at Mallinckrodt Institute of Radiology underwent computed tomography simulation. Images were then transferred to a virtual simulation workstation computer for target contouring. Target gross tumor volumes (GTV) were primary nasopharyngeal tumor (GTVNP) with a prescription of 70 Gy, grossly enlarged cervical nodes (GTVLN) with a prescription of 70 Gy, and the uninvolved cervical lymphatics [designated as the clinical tumor volume (CTV)] with a prescription of 60 Gy. Critical organs, including the parotid gland, spinal cord, brain stem, mandible, and pituitary gland, were also delineated. Conventional beam arrangements were designed following the guidelines of Intergroup (SWOG, RTOG, ECOG) NPC Study 0099 in which the dose was prescribed to the central axis and the target volumes were aimed to receive the prescribed dose ± 10%. Similar dosimetric criteria were used to assess the target volume coverage capability of IMRT. Serial tomotherapy IMRT was planned using a 0.86-cm wide multivane collimator, while a dynamic multileaf collimator system with five equally spaced fixed gantry angles was designated for fixed-beam IMRT. The fractional volume of each critical organ that received a certain predefined threshold dose was obtained from dose-volume histograms of each organ in either the three-dimensional or IMRT treatment planning computer systems. Statistical analysis (paired t -test) was used to examine statistical significance. We found that serial tomotherapy achieved similar target volume coverage as conventional techniques (97.8 ± 2.3% vs. 98.9 ± 1.3%). The static-field IMRT technique (five equally spaced fields) was inferior, with 92.1 ± 8.6% fractional GTVNP receiving 70 Gy ± 10% dose (P < 0.05). However, GTVLN coverage of 70 Gy was significantly better with both IMRT techniques (96.1 ± 3.2%, 87.7 ± 10.6%, and 42.2 ± 21% for tomotherapy, fixed-field IMRT, and conventional therapy, respectively). CTV coverage of 60 Gy was also significantly better with the IMRT techniques. Parotid gland sparing was quantified by evaluating the fractional volume of parotid gland receiving more than 30 Gy; 66.6 ± 15%, 48.3 ± 4%, and 93 ± 10% of the parotid volume received more than 30 Gy using tomotherapy, fixed-field IMRT, and conventional therapy, respectively (P < 0.05). Fixed-field IMRT technique had the best parotid-sparing effect despite less desirable target coverage. The pituitary gland, mandible, spinal cord, and brain stem were also better spared by both IMRT techniques. These encouraging dosimetric results substantiate the theoretical advantage of inverse-planning IMRT in the management of NPC. We showed that target coverage of the primary tumor was maintained and nodal coverage was improved, as compared with conventional beam arrangements. The ability of IMRT to spare the parotid glands is exciting, and a prospective clinical study is currently underway at our institution to address the optimal parotid dose-volume needs to be spared to prevent xerostomia and to improve the quality of life in patients with NPC. © 2001 Wiley-Liss, Inc. [source] ORIGINAL ARTICLE: Sparing of the hippocampus and limbic circuit during whole brain radiation therapy: A dosimetric study using helical tomotherapyJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 4 2010JC Marsh Abstract Introduction:, The study aims to assess the feasibility of dosimetrically sparing the limbic circuit during whole brain radiation therapy (WBRT) and prophylactic cranial irradiation (PCI). Methods and Materials:, We contoured the brain/brainstem on fused MRI and CT as the target volume (PTV) in 11 patients, excluding the hippocampus and the rest of the limbic circuit, which were considered organs at risk (OARs). PCI and WBRT helical tomotherapy plans were prepared for each patient with a 1.0-cm field width, pitch = 0.285, initial modulation factor = 2.5. We attempted to spare the hippocampus and the rest of the limbic circuit while treating the rest of the brain to 30 Gy in 15 fractions (PCI) or 35 Gy in 14 fractions (WBRT) with V100 , 95%. The quality of the plans was assessed by calculating mean dose and equivalent uniform dose (EUD) for OARs and the % volume of the PTV receiving the prescribed dose, V100. Results:, In the PCI plans, mean doses/EUD were: hippocampus 12.5 Gy/14.23 Gy, rest of limbic circuit 17.0 Gy/19.02 Gy. In the WBRT plans, mean doses/EUD were: hippocampus 14.3 Gy/16.07 Gy, rest of limbic circuit 17.9 Gy/20.74 Gy. The mean V100 for the rest of the brain (PTV) were 94.7% (PCI) and 95.1% (WBRT). Mean PCI and WBRT treatment times were essentially identical (mean 15.23 min, range 14.27,17.5). Conclusions:, It is dosimetrically feasible to spare the hippocampus and the rest of the limbic circuit using helical tomotherapy while treating the rest of the brain to full dose. [source] Dosimetric implications of the addition of 18 fluorodeoxyglucose-positron emission tomography in CT-based radiotherapy planning for non-small-cell lung cancerJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 2 2010SK Vinod Summary The aim of this study was to assess the impact of F-18 fluorodeoxyglucose-positron emission tomography (FDG-PET) CT on radiotherapy planning parameters for patients treated curatively with radiotherapy for non-small-cell lung cancer (NSCLC). Five patients with stages I,III NSCLC underwent a diagnostic FDG-PET CT (dPET CT), planning FDG-PET CT (pPET CT) and a simulation CT (RTP CT). For each patient, three radiation oncologists delineated a gross tumour volume based on RTP CT alone, and fused with dPET CT and pPET CT. Standard expansions were used to generate PTVs, and a 3D conformal plan was created. Normal tissue doses were compared between plans. Coverage of pPET CT PTV by the plans based on RTP CT and dPET CT was assessed, and tumour control probabilities were calculated. Mean PTV was similar between RTP CT, dPET CT and pPET CT, although there were significant inter-observer differences in four patients. The plans, however, showed no significant differences in doses to lung, oesophagus, heart or spinal cord. The RTP CT plan and dPET CT plan significantly underdosed the pPET PTV in two patients with minimum doses ranging from 12 to 63% of prescribed dose. Coverage by the 95% isodose was suboptimal in these patients, but this did not translate into poorer tumour control probability. The effect of fused FDG-PET varied between observers. The addition of dPET and pPET did not significantly change the radiotherapy planning parameters. Although FDG-PET is of benefit in tumour delineation, its effect on normal tissue complication probability and tumour control probability cannot be predicted. [source] Centre credentialing for Trans Tasman Radiation Oncology Group trial 06.02: multicentre feasibility study of accelerated partial breast irradiationJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 4 2009T Kron Summary Introduction:, Inconsistencies in contouring target volumes for partial breast irradiation (PBI) may result in geographical misses and compromise treatment outcomes. The present study aimed to (1) determine the variability of the target volumes contoured and treatment plans generated by participating centres in credentialing for participation in a multicentre PBI trial; and (2) assess dosimetric changes when standardized target volumes were used. Methods:, The CT image sets of two de-identified patients post-breast conserving surgery were used. Contouring of the target volumes for the two cases was performed and a treatment plan as per protocol specifications was generated for each case by the seven participating centres. Planning of both cases was repeated by five centres using a set of standardized target volumes to evaluate resulting dosimetric changes in the treatment plans. Results:, The surgical cavity, the part of the planning target volume used for dose evaluation and ipsilateral whole breast volumes contoured by the centres varied by 25%, 16% and 21% (1 standard deviation), respectively. The dosimetric variations found when the standardized target volumes were used were smaller than those noted when centre-specific volumes were used. The volumes of the ipsilateral lungs receiving 30% of the prescribed dose and the volumes of the ipsilateral whole breasts receiving 95% and 50% of the prescribed dose were reduced in the treatment plans developed using the standardized target volumes. Conclusions:, Given the impact of contouring on dose distributions, quality assurance procedures in clinical trials of PBI need to take into account both the technical approaches and the contouring. [source] ,Boomerang' technique: An improved method for conformal treatment of locally advanced nasopharyngeal cancerJOURNAL OF MEDICAL IMAGING AND RADIATION ONCOLOGY, Issue 2 2004June Corry Summary The primary aim of the present study was to assess radiation dosimetry and subsequent clinical outcomes in patients with locally advanced nasopharyngeal cancer using a novel radiation technique termed the ,Boomerang'. Dosimetric comparisons were made with both conventional and intensity modulated radiation therapy (IMRT) techniques. This is a study of 22 patients treated with this technique from June 1995 to October 1998. The technique used entailed delivery of 36 Gy in 18 fractions via parallel opposed fields, then 24 Gy in 12 fractions via asymmetric rotating arc fields for a total of 60 Gy in 30 fractions. Patients also received induction and concurrent chemotherapy. The radiation dosimetry was excellent. Dose,volume histograms showed that with the arc fields, 90% of the planning target volume received 94% of the prescribed dose. Relative to other conventional radiation therapy off-cord techniques, the Boomerang technique results in a 27% greater proportion of the prescribed dose being received by 90% of the planning target volume. This translates into an overall 10% greater dose received for the same prescribed dose. At 3 years, the actuarial loco-regional control rate, the failure-free survival rate and the overall survival rate were 91, 75 and 91%, respectively. At 5 years, the actuarial loco-regional control rate, the failure-free survival rate and the overall survival rate were 74, 62 and 71%, respectively. The Boomerang technique provided excellent radiation dosimetry with correspondingly good loco-regional control rates (in conjunction with chemotherapy) and very acceptable acute and late toxicity profiles. Because treatment can be delivered with conventional standard treatment planning and delivery systems, it is a validated treatment option for centres that do not have the capability or capacity for IMRT. A derivative of the Boomerang technique, excluding the parallel opposed component, is now our standard for patients with locally advanced nasopharyngeal cancer when IMRT is not available. [source] A hierarchical modelling approach to analysing longitudinal data with drop-out and non-compliance, with application to an equivalence trial in paediatric acquired immune deficiency syndromeJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 1 2002Joseph W Hogan Longitudinal clinical trials with long follow-up periods almost invariably suffer from a loss to follow-up and non-compliance with the assigned therapy. An example is protocol 128 of the AIDS Clinical Trials Group, a 5-year equivalency trial comparing reduced dose zidovudine with the standard dose for treatment of paediatric acquired immune deficiency syndrome patients. This study compared responses to treatment by using both clinical and cognitive outcomes. The cognitive outcomes are of particular interest because the effects of human immunodeficiency virus infection of the central nervous system can be more acute in children than in adults. We formulate and apply a Bayesian hierarchical model to estimate both the intent-to-treat effect and the average causal effect of reducing the prescribed dose of zidovudine by 50%. The intent-to-treat effect quantifies the causal effect of assigning the lower dose, whereas the average causal effect represents the causal effect of actually taking the lower dose. We adopt a potential outcomes framework where, for each individual, we assume the existence of a different potential outcomes process at each level of time spent on treatment. The joint distribution of the potential outcomes and the time spent on assigned treatment is formulated using a hierarchical model: the potential outcomes distribution is given at the first level, and dependence between the outcomes and time on treatment is specified at the second level by linking the time on treatment to subject-specific effects that characterize the potential outcomes processes. Several distributional and structural assumptions are used to identify the model from observed data, and these are described in detail. A detailed analysis of AIDS Clinical Trials Group protocol 128 is given; inference about both the intent-to-treat effect and average causal effect indicate a high probability of dose equivalence with respect to cognitive functioning. [source] Influence of genetic variation in CYP3A4 and ABCB1 on dose decrease or switching during simvastatin and atorvastatin therapy,PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 1 2010Matthijs L. Becker PharmD Abstract Purpose Simvastatin and atorvastatin are metabolized by the CYP3A4 enzyme and transported by the ABCB1 transporter. We studied whether the polymorphism CYP3A4*1B and the polymorphisms C1236T, G2677A/T and C3435T in the ABCB1 gene were associated with a decrease of the prescribed dose or a switch to another cholesterol lowering drug during simvastatin and atorvastatin therapy. These events may indicate that statin plasma levels were too high and resulted in an adverse drug reaction or a too strong reduction in cholesterol level. Methods We identified 1239 incident simvastatin and atorvastatin users in the Rotterdam Study, a population-based cohort study. Associations between the polymorphisms in the CYP3A4 and ABCB1 gene and the time to a decrease in dose or a switch to another cholesterol lowering drug were studied using Cox proportional hazards. Results Simvastatin and atorvastatin users with the CYP3A4*1B variant G allele had a lower risk (HR 0.46; 95%CI 0.24,0.90) for these events than users with the wild-type AA genotype. No significant associations were found for the ABCB1 polymorphisms. The association with the CYP3A4*1B polymorphism was found in women (HR 0.33; 95%CI 0.12,0.89) and was non-significant in men (HR 0.69 95%CI 0.28,1.70). This association was stronger in patients with the ABCB1 3435T variant allele versus the G allele. Conclusion In simvastatin and atorvastatin users, the CYP3A4*1B G allele is associated with a lower risk of elevated statin plasma levels, particularly in women and in users with the ABCB1 3435T variant allele. Copyright © 2009 John Wiley & Sons, Ltd. [source] Long-term utility of measuring adherence by self-report compared with pharmacy record in a routine clinic settingHIV MEDICINE, Issue 5 2005CK Fairley Objectives To compare long-term adherence to antiretroviral therapy in an HIV service, as measured by self-report and by pharmacy records. To determine the level of adherence by each measure required to suppress viral load in a majority of patients. Methods The percentage of prescribed doses taken was calculated from (a) the number of missed doses in the previous 28 days reported by patients in a questionnaire at each clinic visit, and (b) pharmacy dispensing records. These were compared with each other and with HIV viral load data. Results Mean adherence was 96.2% by pharmacy record over 44 months and 98.6% by self-report over 25 months. The two methods correlated with each other (P<0.001) and the proportion of patients with viral load <400 HIV-1 RNA copies/mL increased with adherence as measured by self-report (P=0.001) and pharmacy record (P=0.004). Fewer than 60% of patients always had viral loads <400 copies/mL if adherence fell below 95% (pharmacy record) or 97% (self-report). Adherence was higher for once-daily than for twice-daily therapy (by pharmacy record: 97.2% vs. 96.0%; P<0.001). Adherence by both measures increased over time. Conclusions Self-reported antiretroviral adherence correlates with pharmacy dispensing records and predicts suppression of viral load at levels ,97%. It is practical to adopt this into routine HIV clinical care. [source] An unusual cause of dizziness in bulimia nervosa: A case reportINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 4 2005Randy A. Sansone MD Abstract Objective The current article describes the case of a 23<->year<->old female with purging<->type bulimia nervosa who was evaluated by her primary care physician for dizziness and lightheadedness. Methods After laboratory studies were performed by her primary care physician, the patient was admitted to the hospital because of severe anemia. The patient had been taking nonsteroidal antiinflammatory drugs <(>NSAIDS<)> at prescribed doses for shin splints that were secondary to jogging and developed gastric erosion. Results Endoscopic examination showed that she had diffuse gastritis with linear, streaky ulcerations throughout the body of the stomach. Discussion Lightheadedness is a common clinical symptom among individuals with eating disorders, but is typically related to dehydration, malnutrition, hypometabolism, andor combinations of these factors. Clinicians need to consider NSAID use, which may cause erosive gastritis, blood loss, and lightheadedness. © 2005 by Wiley Periodicals, Inc. [source] | ||||||||||