Comparison of anatomy-based, fluence-based and aperture-based treatment planning approaches for VMAT

Volumetric modulated arc therapy (VMAT) has the potential to reduce treatment times while producing comparable or improved dose distributions relative to fixed-field intensity-modulated radiation therapy. In order to take full advantage of the VMAT delivery technique, one must select a robust inverse planning tool. The purpose of this study was to evaluate the effectiveness and efficiency of VMAT planning techniques of three categories: anatomy-based, fluence-based and aperture-based inverse planning. We have compared these techniques in terms of the plan quality, planning efficiency and delivery efficiency. Fourteen patients were selected for this study including six head-and-neck (HN) cases, and two cases each of prostate, pancreas, lung and partial brain. For each case, three VMAT plans were created. The first VMAT plan was generated based on the anatomical geometry. In the Elekta ERGO++ treatment planning system (TPS), segments were generated based on the beam's eye view (BEV) of the target and the organs at risk. The segment shapes were then exported to Pinnacle TPS followed by segment weight optimization and final dose calculation. The second VMAT plan was generated by converting optimized fluence maps (calculated by the Pinnacle TPS) into deliverable arcs using an in-house arc sequencer. The third VMAT plan was generated using the Pinnacle SmartArc IMRT module which is an aperture-based optimization method. All VMAT plans were delivered using an Elekta Synergy linear accelerator and the plan comparisons were made in terms of plan quality and delivery efficiency. The results show that for cases of little or modest complexity such as prostate, pancreas, lung and brain, the anatomy-based approach provides similar target coverage and critical structure sparing, but less conformal dose distributions as compared to the other two approaches. For more complex HN cases, the anatomy-based approach is not able to provide clinically acceptable VMAT plans while highly conformal dose distributions were obtained using both aperture-based and fluence-based inverse planning techniques. The aperture-based approach provides improved dose conformity than the fluence-based technique in complex cases.     

Merkel cell carcinoma

Merkel cell carcinoma is a rare, highly aggressive neuroendocrine cutaneous neoplasm with a variable clinical presentation. Histologically, it is a predominantly dermal-based lesion composed of monotonous small round cells with scanty cytoplasm, often difficult to differentiate from small round cell tumors, metastatic small cell carcinoma, blastic hematologic malignancies, and melanoma. The malignant cells express both epithelial and neuroendocrine immunohistochemical markers, a unique feature that helps differentiate this neoplasm from other entities. The pathogenesis of Merkel cell carcinoma has remained a mystery despite its association with various chromosomal abnormalities and with growth signaling and apoptotic pathways. The discovery of the Merkel cell polyomavirus suggests another clue to its pathogenesis. This virus integrates into band 3p14 and promotes carcinogenesis by altering the activity of tumor suppressor and cell cycle regulatory proteins. This discovery of the Merkel cell polyomavirus may greatly enhance our understanding of this rare aggressive neoplasm and allow further advancements in treatment.     

Small peptide analogue of SDF-1alpha supports survival of cord blood CD34+ cells in synergy with other cytokines and enhances their ex vivo expansion and engraftment into nonobese diabetic/severe combined immunodeficient mice

The SDF-1/CXCR4 axis has been implicated in the chemotaxis, homing, mobilization, and expansion of hematopoietic stem and progenitor cells. We studied the effects of a SDF-1 peptide analogue CTCE-0214 on the survival of cord blood CD34+ cells in culture, expansion, and engraftment of expanded cells in the nonobese diabetic/severe combined immunodeficient (NOD/SCID) mouse model. Our results demonstrated that CTCE-0214 synergized with thrombopoietin (TPO), stem cell factor (SCF), or flt-3 ligand (FL) on the survival of stem and progenitor cells in culture. Adding CTCE-0214 at a low concentration (0.01 ng/ml) for 4 days together with TPO, SCF, and FL significantly enhanced ex vivo expansion of CD34+ cells to subsets of primitive (CD34+CD38- cells, colony-forming unit-mixed [CFU-GEMMs]), erythroid (CFU-Es), myeloid (CFU-GMs), and megakaryocytic (CD61+CD41+ cells, CFU-MKs) progenitors, as well as their multilineage engraftment in NOD/SCID mice. Interestingly, the short exposure of expanded cells to CTCE-0214 (100 and 500 ng/ml) for 4 hours did not increase the quantity of progenitor cells but enhanced their engraftment capacity. The proportion of CD34+ cells expressing surface CXCR4 was decreased, but the overall number of this population increased upon expansion. The small peptide analogue of SDF-1 could be developed for ex vivo expansion and improving engraftment of cord blood transplantation.     

Gene-gene interactions for asthma and plasma total IgE concentration in Chinese children

BACKGROUND: Asthma is a complex disease resulting from interactions between multiple genes and environmental factors. Study of gene-gene interactions could provide insight into asthma pathophysiology. OBJECTIVE: We investigated the interaction among 12 different loci in 8 candidate genes and asthma and increased plasma total IgE concentrations in 240 Chinese asthmatic subjects and 140 control subjects. METHODS: Genotyping was performed by means of RFLP analysis. Multifactor dimensionality reduction and logistic regression were used to analyze gene-gene interactions. RESULTS: A significant interaction was found between R130Q in the IL-13 gene (IL13) and I50V in the IL-4 receptor alpha gene (IL4RA) on the risk of asthma, with a cross-validation consistency of 10 of 10 and a prediction error of 33.7% (P = .014). The odds ratio of the high-risk to low-risk group was 2.6 (95% CI, 1.4-5.0; P = .004). For increased plasma total IgE concentration, the best 2-locus model consisted of R130Q in IL13 and C-431T in the thymus and activation-regulated chemokine gene (TARC). This model showed a maximum cross-validation consistency of 10 and a minimum prediction error of 36.1% (P = .022). The odds ratio of the high-risk to low-risk group was 3.9 (95% CI, 2.0-7.7; P = .0001). Logistic regression revealed significant interactions between IL13 and IL4RA for asthma (P = .042) and IL13 and TARC for increased total IgE concentration (P = .012). CONCLUSIONS: Our data suggest significant interactions between IL13 and IL4RA for asthma and IL13 and TARC for increased plasma total IgE concentrations in Chinese children.     

No association between VNTR polymorphisms of dopamine transporter gene and attention deficit hyperactivity disorder in Chinese children.

Dopamine transporter (DAT) gene is implicated in the pathogenesis of attention deficit hyperactivity disorder (ADHD). Previously a meta-analysis concluded no association between the variable-number-of-tandem-repeats (VNTR) polymorphisms of the DAT gene and ADHD. However, significant heterogeneity was present among studies and no conclusion can be drawn about the association in any single ethnicity given the small number of studies. There were also conflicting results in Chinese populations. We therefore perform the present study to investigate the association in Chinese children in Hong Kong. In this prospective family-based and case-control study during January to June 2004, we recruited consecutive Chinese children diagnosed with ADHD by DSM-IV criteria, their family members, and sex-matched controls admitted for acute upper respiratory infection, excluding those with perinatal brain insults, mental retardation, or neurological deficits. VNTR polymorphisms of the DAT gene were determined by standard PCR followed by agarose gel electrophoresis. Sixty-four ADHD cases (52 boys, 12 girls), their family members and 64 normal controls were recruited. The 10-repeat allele (92.6%) and the 10/10 repeat genotype (85.2%) were the most prevalent. Both family-based and case-control analyses showed no association between the DAT gene polymorphisms and ADHD (transmission dysequilibrium test: P = 0.99; odds ratio of 10-repeat allele = 0.89 (95%CI 0.35-2.28), P = 0.81; odds ratio of 10/10 repeat genotype = 0.69 (95%CI 0.26-1.84), P = 0.46). We concluded that VNTR polymorphism of the DAT gene is not associated with ADHD in Chinese children, and further studies are needed to clarify the polygenic and environmental influences for pathogenesis of ADHD.     

Membrane potentials in Rana temporaria muscle fibres in strongly hypertonic solutions

Conventional microelectrode methods were used to measure variations in resting membrane potentials, E _m, of intact amphibian skeletal muscle fibres over a wide range of increased extracellular tonicities produced by inclusion of varying extracellular concentrations of sucrose. Moderate increases in extracellular tonicity to up to 2.6× normal (2.6τ) under Cl⁻ free conditions produced negative shifts in E _m that followed expectations for the K⁺ Nernst equation (E _K) applied to a perfect osmometer containing a conserved intracellular K⁺ content despite any accompanying cell volume change. In contrast, E _m remained stable in fibres studied in otherwise similar Cl⁻ containing solutions, consistent with E _m stabilization despite negative shifts in E _K through inward cation-Cl⁻ co-transport activity. Short exposures to higher tonicities (>3τ) similarly produced negative shifts in E _m in Cl⁻ free but not Cl⁻ containing solutions. However, prolonged exposures to solutions of >3τ caused gradual net positive changes in E _m in both Cl⁻ containing and Cl⁻ free solutions suggesting that these changes were independent of cation-Cl⁻ transport. Indeed, there was no evidence of cation-Cl⁻ co-transport activity in strongly hypertonic solutions despite its predicted energetic favourability, suggesting its possible regulation by E _m in muscle. Additional findings implicated a failure to maintain greatly increased transmembrane [K⁺] gradients in these E _m changes. Thus: (1) halving or doubling [K⁺]_e produced negative or positive shifts␣in E _m, respectively in isotonic or moderately hypertonic (<2.7τ), but not strongly hypertonic (>3τ) solutions; (2) subsequent restoration of isotonic extracellular conditions produced further positive changes in E _m consistent with a dilution of the depleted [K⁺]_i by fibres regaining their original resting volumes; (3) quantitative modelling similarly predicted a gradual net efflux of K⁺ as the balance between active and passive [K⁺] fluxes altered due to increased transmembrane [K⁺] gradients in hypertonic and low [K⁺]_e solutions. However, the observed positive changes in E _m in the most strongly hypertonic solutions eventually exceeded these predictions suggesting additional limitations on␣Na⁺/K⁺-ATPase activity in strongly hypertonic solutions.James A. Fraser and Kai Yuen Wong have equally contributed to this paper.     

Effect of local lignocaine gel application for pain relief during suction termination of first-trimester pregnancy: a randomized controlled trial

BACKGROUND: This study evaluated the effectiveness of local lignocaine gel application in pain control during first-trimester suction termination of pregnancy (STOP). METHODS: In this prospective randomized placebo-controlled double-blind trial, 131 women undergoing STOP between 7 and 10 weeks of gestation were studied. They were computer-randomized to receive 2% lignocaine gel or placebo (KY Jelly) locally applied to the cervix 1 min before cervical manipulation/dilatation. They all had cervical priming with misoprostol and premedication with diazepam and pethidine. Pain scores on a verbal analogue scale preoperative, at cervical manipulation/dilatation, intraoperative and 1 h post-operative, as well as the patients' satisfaction level towards pain control, were compared. RESULTS: The lignocaine gel group had significantly reduced overall intraoperative pain score compared with placebo group (P = 0.021). No significant difference in pain score between the two groups was demonstrated at other time points. Subgroup analysis revealed that the difference in overall intraoperative pain scores between the two groups was evident in the multiparous (P = 0.015) but not the nulliparous subjects. CONCLUSION: The use of local lignocaine gel application reduces overall intraoperative pain in multiparous women undergoing first-trimester STOP preceded by misoprostol cervical priming and premedication for conscious sedation.     

Molecular-clinical correlations in a family with variable tissue mitochondrial DNA T8993G mutant load

Unlike many pathogenic mitochondrial DNA mutations, the T8993G mutation associated with Leigh syndrome (LS) and neurogenic muscle weakness, ataxia, retinitis pigmentosa (NARP) typically shows little variation in mutant load between different tissue types. We describe the molecular and clinical findings in a family with variable disease severity and tissue T8993G mutant loads. Real-time ARMS qPCR testing showed that two brothers with features of NARP and LS had high mutant loads (>90%) in all tissues tested, similar to previously reported cases. Their sister, who has mild speech delay but attends normal school, was found to have a relatively high mutant load (mean 93%) in tissues derived from endoderm (buccal mucosa) and mesoderm (blood and skin fibroblasts). However, in tissue derived from ectoderm (hair bulbs), she carried a considerably lower proportion of mutant mtDNA. Because both surface ectoderm, which gives rise to outer epithelia and hair, and neuroectoderm, which gives rise to the central nervous system, are derived from ectoderm, it is tempting to speculate that the mutant load detected in the oligosymptomatic sister's hair bulbs is a reflection of the brain mutant load. We conclude that significant variation in tissue mutant load may occur in at least some individuals that harbor the T8993G mutation. This adds additional complexity to genetic counseling and prenatal diagnosis in such instances. Given the shared embryonic origin of hair bulbs and brain, we recommend performing hair bulb mtDNA analysis in asymptomatic or oligosymptomatic individuals that have high blood mutant loads in order to understand better the genotype-phenotype correlations related to the T8993G mutation.     

Effects of high dose of simvastatin on levels of dopamine and its reuptake in prefrontal cortex and striatum among SD rats

Statins are increasingly being used for the treatment of a variety of conditions beyond their original indication for cholesterol lowering. We previously reported that simvastatin increased dopamine receptors in the rat prefrontal cortex [Q. Wang, W.L. Ting, H. Yang, P.T. Wong, High doses of simvastatin upregulate dopamine D₁ and D₂ receptor expression in the rat prefrontal cortex: possible involvement of endothelial nitric oxide synthase, Br. J. Pharmacol. 144 (2005) 933–939] and restored its downregulation in a model of Parkinson's disease (PD) [Q. Wang, P.H. Wang, C. McLachlan, P.T. Wong, Simvastatin reverses the downregulation of dopamine D1 and D2 receptor expression in the prefrontal cortex of 6-hydroxydopamine-induced Parkinsonian rats, Brain Res. 1045 (2005) 229–233]. Here we explore the effects of simvastatin treatment on tissue dopamine content and reuptake. Sprague–Dawley rats were given simvastatin (1 and 10 mg kg⁻¹ day⁻¹, p.o.) for 4 weeks. Brain tissue from prefrontal cortex and striatum were taken out for dopamine content and its reuptake. Using high-performance liquid chromatographic-mass spectrometer (HPLC-MS), simvastatin (10 mg kg⁻¹ day⁻¹) was found to increase dopamine content by 110% in the striatum but decreased by 76% in the prefrontal cortex compared with the saline treated group. Dopamine (DA) reuptake was unchanged in both brain regions. These results suggest that chronic treatment with high dose of simvastatin may affect DA tissue level in prefrontal cortex and striatum without changing on DA reuptake. This may have important clinical implications in psychiatric and striatal dopaminergic disorders.     

Over-expression of c-erbB-2 correlates with nuclear morphometry and prognosis in breast carcinoma in Asian women

AIM: We aimed to investigate the immunohistochemical expression of c-erbB-2 in invasive breast carcinoma in Asian women and its correlations with clinicopathological parameters and nuclear morphometry. Patients were followed up for disease relapse and overall survival, and the data were reviewed in conjunction with c-erbB-2 over-expression. METHODS: Paraffin sections from 321 invasive breast cancers were immunohistochemically stained with anti-human c-erbB-2 antibody using the streptavidin-biotin technique. RESULTS: c-erbB-2 was over-expressed in 110 (34.3%) cases, with an inverse correlation with oestrogen receptor (ER) and progesterone receptor (PR) status (p=0.0001) and a positive correlation with histological grade (p=0.017). Nuclear morphometry in 96 cases revealed rounder nuclei in c-erbB-2 negative tumours (p=0.0322) when compared with c-erbB-2 positive tumours. Among c-erbB-2 positive cases, malignant cells of histological grade 3 tumours revealed larger nuclear area and perimeter than grade 1 and 2 cases (p=0.0095, p=0.03, respectively) while increasing tumour size correlated with greater nuclear perimeter (p=0.046). c-erbB-2 positivity was significantly associated with poor survival when all patients were included in the analysis (p=0.0166) and for subsets of node positive, histological grade 1 and 2, and ER positive tumours, and in women aged over 50 years (p=0.0047, p=0.0367, p=0.0092, p=0.0096, respectively). CONCLUSIONS: c-erbB-2 was independently prognostic when histological grade, nodal and ER status were considered. Our results show that c-erbB-2 over-expression correlates with poor histological grade and negative ER/PR status, and predicts poor overall survival in Asian women with breast cancer.