Incorporating an improved dose-calculation algorithm in conformal radiotherapy of lung cancer: re-evaluation of dose in normal lung tissue.

BACKGROUND AND PURPOSE: The low density of lung tissue causes a reduced attenuation of photons and an increased range of secondary electrons, which is inaccurately predicted by the algorithms incorporated in some commonly available treatment planning systems (TPSs). This study evaluates the differences in dose in normal lung tissue computed using a simple and a more correct algorithm. We also studied the consequences of these differences on the dose-effect relations for radiation-induced lung injury. MATERIALS AND METHODS: The treatment plans of 68 lung cancer patients initially produced in a TPS using a calculation model that incorporates the equivalent-path length (EPL) inhomogeneity-correction algorithm, were recalculated in a TPS with the convolution-superposition (CS) algorithm. The higher accuracy of the CS algorithm is well-established. Dose distributions in lung were compared using isodoses, dose-volume histograms (DVHs), the mean lung dose (MLD) and the percentage of lung receiving >20 Gy (V20). Published dose-effect relations for local perfusion changes and radiation pneumonitis were re-evaluated. RESULTS: Evaluation of isodoses showed a consistent overestimation of the dose at the lung/tumor boundary by the EPL algorithm of about 10%. This overprediction of dose was also reflected in a consistent shift of the EPL DVHs for the lungs towards higher doses. The MLD, as determined by the EPL and CS algorithm, differed on average by 17+/-4.5% (+/-1SD). For V20, the average difference was 12+/-5.7% (+/-1SD). For both parameters, a strong correlation was found between the EPL and CS algorithms yielding a straightforward conversion procedure. Re-evaluation of the dose-effect relations showed that lung complications occur at a 12-14% lower dose. The values of the TD(50) parameter for local perfusion reduction and radiation pneumonitis changed from 60.5 and 34.1 Gy to 51.1 and 29.2 Gy, respectively. CONCLUSIONS: A simple tissue inhomogeneity-correction algorithm like the EPL overestimates the dose to normal lung tissue. Dosimetric parameters for lung injury (e.g. MLD, V20) computed using both algorithms are strongly correlated making an easy conversion feasible. Dose-effect relations should be refitted when more accurate dose data is available.     

First results of a phase I/II dose escalation trial in non-small cell lung cancer using three-dimensional conformal radiotherapy.

PURPOSE: To evaluate the feasibility of dose escalation in non-small cell lung cancer (NSCLC) using three-dimensional conformal radiation therapy. PATIENTS AND METHODS: The main eligibility criteria of the trial were: pathologically proven inoperable NSCLC, ECOG performance status or=grade 3 (SWOG), grade 3 early and grade 2 late esophageal toxicity or any other (RTOG) grade 3 or 4 complications). RESULTS: Fifty-five patients were included. Tumor stage was I/II in 47%, IIIA in 33% and IIIB in 20%. The majority of the patients received a dose of 74.3 Gy (n=17) or 81.0 Gy (n=23). Radiation pneumonitis occurred in seven patients: four patients developed a grade 2, two patients grade 3 and one patient a grade 4. Esophageal toxicity was mild. In 50 patients tumor response at 3 months follow-up was evaluable. In six patients a complete response was recorded, in 38 a partial response, five patients had stable disease and one patient experienced progressive disease. Only one patient developed an isolated failure in an uninvolved nodal area. So far the radiation dose was safely escalated to 87.8 Gy in group 1 (lowest rMLD), 81.0 Gy in groups 2 and 3 and 74.3 Gy in group 4. CONCLUSION: Three-dimensional conformal radiotherapy enables significant dose escalation in NSCLC. The maximum tolerable dose has not yet been reached in any risk group.     

Early versus late parenteral nutrition in ICU patients: cost analysis of the EPaNIC trial

ABSTRACT: INTRODUCTION: The EPaNIC randomized controlled multicentre trial showed that postponing initiation of parenteral nutrition (PN) in ICU-patients to beyond the first week (Late-PN) enhanced recovery, as compared with Early-PN. This was mediated by fewer infections, accelerated recovery from organ failure and reduced duration of hospitalization. Now, the trial's preplanned cost analysis (N = 4640) from the Belgian healthcare payers' perspective is reported. METHODS: Cost data were retrieved from individual patient invoices. Undiscounted total healthcare costs were calculated for the index hospital stay. A cost tree based on acquisition of new infections and on prolonged length-of-stay was constructed. Contribution of 8 cost categories to total hospitalization costs was analyzed. The origin of drug costs was clarified in detail through the Anatomical Therapeutic Chemical (ATC) classification system. The potential impact of Early-PN on total hospitalization costs in other healthcare systems was explored in a sensitivity analysis. RESULTS: ICU-patients developing new infection (24.4%) were responsible for 42.7% of total costs, while ICU-patients staying beyond one week (24.3%) accounted for 43.3% of total costs. Pharmacy-related costs represented 30% of total hospitalization costs and were increased by Early-PN (+608.00 EUR/patient, p = 0.01). Notably, costs for ATC-J (anti-infective agents) (+227.00 EUR/patient, p = 0.02) and ATC-B (comprising PN) (+220.00 EUR/patient, p = 0.006) drugs were increased by Early-PN. Sensitivity analysis revealed a mean total cost increase of 1,210.00 EUR/patient (p = 0.02) by Early-PN, when incorporating the full PN costs. CONCLUSIONS: The increased costs by Early-PN were mainly pharmacy-related and explained by higher expenditures for PN and anti-infective agents. The use of Early-PN in critically ill patients can thus not be recommended for both clinical (no benefit) and cost-related reasons. TRIAL REGISTRATION: ClinicalTrials.gov NCT00512122.     

Patterns in the prevalence of diabetes and incidence of diabetic complications in people with and without an intellectual disability in Dutch primary care: Insights from a population-based data-linkage study

AimsTo conduct an epidemiological analysis of patterns observed in diabetes care provided to individuals with and without intellectual disabilities (ID) in primary care settings.MethodsAn ID-cohort (N = 21,203) was compared with a control group of similar age and sex from the general Dutch population (N = 267,628). Distinctive data for diabetes (both type 1 and type 2) and related complications were retrieved from national databases.ResultsThe prevalence of diabetes was higher in people with ID than in the general population (9.9% versus 6.6%). Largest differences were seen in younger age groups. Women with ID had diabetes more often than men with ID. Complications were less common in people with ID than in the general population (IR 58.6 vs. 70.4). In particular, cardiological complications were noted less, while surgical interventions and hospitalization occurred more often.ConclusionsAlthough diabetes was 1.5 times more prevalent in people with ID than in other people, related complications were less common, followed different patterns and were more severe than in the general population. Future research is needed to understand of the underlying causal mechanisms and to lower the risk of severe diabetic complications among people with ID.     

Synthesis and Characterization of Holmium-Doped Iron Oxide Nanoparticles

Rare earth atoms exhibit several interesting properties, for example, large magnetic moments and luminescence. Introducing these atoms into a different matrix can lead to a material that shows multiple interesting effects. Holmium atoms were incorporated into an iron oxide nanoparticle and the concentration of the dopant atom was changed in order to determine its influence on the host crystal. Its magnetic and magneto-optical properties were investigated by vibrating sample magnetometry and Faraday rotation measurements. The luminescent characteristics of the material, in solution and incorporated in a polymer thin film, were probed by fluorescence experiments.     

Plant cytokinin analogues with inhibitory activity on cyclin-dependent kinases exert their antiproliferative effect through induction of apoptosis initiated by the mitochondrial pathway: determination by a multiparametric flow cytometric analysis

OBJECTIVE: Regulation of the cell cycle by cyclin-dependent kinase (CDK) activity occurs at multiple levels and is often altered in human cancers. Therefore, CDK activity has been targeted for drug discovery, and a number of small molecules have now been identified as CDK inhibitors. Plant cytokinin analogues with CDK inhibitory activity and antiproliferative effects were studied to characterize the cellular basis of the cytotoxic effect. METHODS: The IC(50) value (concentration at which 50% of the cell proliferation is inhibited) and AC(50) value (concentration at which 50% of the cell population is apoptotic) were determined by flow cytometry and microscopy, respectively. A new multiparametric flow cytometric analysis was used to study the sequence of different apoptotic events. In this assay, analysis of phosphatidylserine exposure, mitochondrial membrane depolarization, activation of caspases and DNA condensation were combined. RESULTS: Treatment of Jurkat and KG1 cells with the CDK inhibitors results in a decrease of viable cells and a parallel increase in percentage of apoptotic cells. Apoptosis was accompanied by a rapid decrease of mitochondrial membrane potential, which precedes DNA condensation, exposure of phosphatidylserine and activation of caspases. CONCLUSIONS: The main cellular mechanism of the antiproliferative effect of plant cytokinin analogues with CDK inhibitory activity is the induction of apoptosis. The multiparametric flow cytometric technique allowed to follow the kinetics of various aspects of apoptotic cell changes and demonstrated that cytokinin analogue-induced apoptosis starts through the mitochondrial pathway. This technique could also become of value for the rapid screening of pro-apoptotic properties of chemotherapeutic compounds.     

Lower anticoagulation for mechanical heart valves: experience with the ATS bileaflet valve

Background: The design of the bileaflet ATS (ATS Medical Inc., Minneapolis, USA) mechanical valve incorporates an open pivot at the hinge mechanism. Total washout of the blood at the pivot area was observed using 3-D computational fluid dynamics modelling. This phenomenon could make the valve less vulnerable to clot formation in patients without major thromboembolic risk factors.

Methods: From January 1993 to June 1999, 286 consecutive patients had the ATS valve inserted in the aortic position. Patients were divided into two groups. Group 1 comprised all patients in regular sinus rhythm with good left ventricular function (144 patients). Group 2 included patients in non-sinus rhythm and/or with large hypocontractile left ventricles (142 patients). The anticoagulation regime in group 1 was used to obtain an international normalised ratio (INR) between 1.5 and 2.5. This contrasts with our regular aim to maintain the INR strictly between 2.5 and 3.5 for all mechanical valves, as achieved in group 2.

Results: The follow-up period (99% completeness) ranged from 18 to 84 months. Survival (Kaplan-Meier) was 97 and 98% and 92 and 81% at 1 and 5 years in group 1 and group 2, respectively (P = 0.12). Log rank analysis failed to detect a statistical difference in thromboembolism or bleeding between both groups (P > 0.05). However, trends were in favour of group 1. Univariate analysis selected poor ventricular function and an ‘erratic’ INR value (P = 0.002) as risk factors for death. The sole independent risk factor for bleeding was the use of aspirin (P = 0.025).

Conclusions: The excellent group 1 data and outcome encouraged us to continue our low intensive anticoagulation regime and perhaps should be regarded as a new concept for treatment of selected mechanical valve patients.