'I Don't Like Uncertainty, I Like to Know': How and why uveal melanoma patients consent to life expectancy prognostication.

BACKGROUND: Technological advances have led to cancer prognostication that is increasingly accurate but often unalterable. However, a reliable prognosis of limited life expectancy can cause psychological distress. People should carefully consider offers of prognostication, but little is known about how and why they decide on prognostication. Using uveal melanoma (UM) patients, we aimed to identify (i) how and why do people with UM decide to accept prognostication and (ii) alignment and divergence of their decision-making from conceptualizations of a 'well-considered' decision. METHODS: UM provides a paradigm to elucidate clinical and ethical perspectives on prognostication, because prognostication is reliable but prognoses are largely nonameliorable. We used qualitative methods to examine how and why 20 UM people with UM chose prognostication. We compared findings to a template of 'well-considered' decision-making, where 'well-considered' decisions involve consideration of all likely outcomes. RESULTS: Participants wanted prognostication to reduce future worry about uncertain life expectancy. They spontaneously spoke of hoping for a good prognosis when making their decisions, but largely did not consider the 50% possibility of a poor prognosis. When pressed, they argued that a poor outcome at least brings certainty. CONCLUSIONS: While respecting decisions as valid expressions of participants' wishes, we are concerned that they did not explicitly consider the realistic possibility of a poor outcome and how this would affect them. Thus, it is difficult to see their decisions as 'well-considered'. We propose that nondirective preference exploration techniques could help people to consider the possibility of a poor outcome. PATIENT OR PUBLIC CONTRIBUTION: This paper is a direct response to a patient-identified and defined problem that arose in therapeutic and conversational discourse. The research was informed by the responses of patient participants, as we used the material from interviews to dynamically shape the interview guide. Thus, participants' ideas drove the analysis and shaped the interviews to come.

Prediction of all-cause mortality from 24 month trajectories in patient-reported psychological, clinical and quality of life outcomes in uveal melanoma patients.

A number of patient-reported outcomes (PROs) predict increased mortality after primary cancer treatment. Studies, though, are sometimes affected by methodological limitations. They often use control variables that poorly predict life expectancy, examine only one or two PROs thus not controlling potential confounding by unmeasured PROs, and observe PROs at only a single point in time. To predict all-cause mortality, this study used control variables affording good estimates of life expectancy, conducted multivariate analyses of multiple PROs to identify independent predictors, and monitored PROs two years after diagnosis. We recruited a consecutive sample of 824 patients with uveal melanoma between April 2008 and December 2014. PROs were variables shown to predict mortality in previous studies; anxiety, depression, visual and ocular symptoms, visual function impairment, worry about cancer recurrence, and physical, emotional, social and functional quality of life (QoL), measured 6, 12 and 24 months after diagnosis. We conducted Cox regression analyses with a census date of December 2018. Covariates were age, gender, marital and employment status, self-reported co-morbidities, tumor diameter and thickness, treatment modality and chromosome 3 mutation status, the latter a genetic mutation strongly associated with mortality. Single predictor analyses (with covariates), showed 6-month depression and poorer functional QoL predicting mortality, as did 6-12 month increases in anxiety and 6-12 month decreases in physical and functional QoL. Multivariate analyses using all PROs showed independent prediction by 6-month depression and decreasing QoL over 6-12 months and 12-24 months. Elevated depression scores six months post-diagnosis constituted an increased mortality risk. Early intervention for depressive symptoms may reduce mortality.

Imaging acute effects of bevacizumab on tumor vascular kinetics in a preclinical orthotopic model of U251 glioma.

The effect of a human vascular endothelial growth factor antibody on the vasculature of human tumor grown in rat brain was studied. Using dynamic contrast-enhanced magnetic resonance imaging, the effects of intravenous bevacizumab (Avastin; 10 mg/kg) were examined before and at postadministration times of 1, 2, 4, 8, 12 and 24 h (N = 26; 4-5 per time point) in a rat model of orthotopic, U251 glioblastoma (GBM). The commonly estimated vascular parameters for an MR contrast agent were: (i) plasma distribution volume (vp ), (ii) forward volumetric transfer constant (Ktrans ) and (iii) reverse transfer constant (kep ). In addition, extracellular distribution volume (VD ) was estimated in the tumor (VD-tumor ), tumor edge (VD-edge ) and the mostly normal tumor periphery (VD-peri ), along with tumor blood flow (TBF), peri-tumoral hydraulic conductivity (K) and interstitial flow (Flux) and tumor interstitial fluid pressure (TIFP). Studied as % changes from baseline, the 2-h post-treatment time point began showing significant decreases in vp , VD-tumor, VD-edge and VD-peri , as well as K, with these changes persisting at 4 and 8 h in vp , K, VD-tumor, -edge and -peri (t-tests; p < 0.05-0.01). Decreases in Ktrans were observed at the 2- and 4-h time points (p < 0.05), while interstitial volume fraction (ve ; = Ktrans /kep ) showed a significant decrease only at the 2-h time point (p < 0.05). Sustained decreases in Flux were observed from 2 to 24 h (p < 0.01) while TBF and TIFP showed delayed responses, increases in the former at 12 and 24 h and a decrease in the latter only at 12 h. These imaging biomarkers of tumor vascular kinetics describe the short-term temporal changes in physical spaces and fluid flows in a model of GBM after Avastin administration.

miR-183-96-182 Cluster Is Involved in Invariant NKT Cell Development, Maturation, and Effector Function.

The development, differentiation and function of invariant NKT (iNKT) cells require a well-defined set of transcription factors, but how these factors are integrated to each other and the detailed signaling networks remain poorly understood. Using a Dicer-deletion mouse model, our previous studies have demonstrated the critical involvement of microRNAs (miRNAs) in iNKT cell development and function, but the role played by individual miRNAs in iNKT cell development and function is still not clear. In this study, we show the dynamic changes of miRNA 183 cluster (miR-183C) expression during iNKT cell development. Mice with miR-183C deletion showed a defective iNKT cell development, sublineage differentiation, and cytokine secretion function. miRNA target identification assays indicate the involvement of multiple target molecules. Our study not only confirmed the role of miR-183C in iNKT cell development and function but also demonstrated that miR-183C achieved the regulation of iNKT cells through integrated targeting of multiple signaling molecules and pathways.

Adaptation of laser interstitial thermal therapy for tumor ablation under MRI monitoring in a rat orthotopic model of glioblastoma.

BACKGROUND: Laser interstitial thermal therapy (LITT) under magnetic resonance imaging (MRI) monitoring is being increasingly used in cytoreductive surgery of recurrent brain tumors and tumors located in eloquent brain areas. The objective of this study was to adapt this technique to an animal glioma model. METHODS: A rat model of U251 glioblastoma (GBM) was employed. Tumor location and extent were determined by MRI and dynamic contrast-enhanced (DCE) MRI. A day after assessing tumor appearance, tumors were ablated during diffusion-weighted imaging (DWI)-MRI using a Visualase LITT system (n = 5). Brain images were obtained immediately after ablation and again at 24 h post-ablation to confirm the efficacy of tumor cytoablation. Untreated tumors served as controls (n = 3). Rats were injected with fluorescent isothiocyanate (FITC) dextran and Evans blue that circulated for 10 min after post-LITT MRI. The brains were then removed for fluorescence microscopy and histopathology evaluations using hematoxylin and eosin (H&E) and major histocompatibility complex (MHC) staining. RESULTS: All rats showed a space-occupying tumor with T2 and T1 contrast-enhancement at pre-LITT imaging. The rats that underwent the LITT procedure showed a well-demarcated ablation zone with near-complete ablation of tumor tissue and with peri-ablation contrast enhancement at 24 h post-ablation. Tumor cytoreduction by ablation as seen on MRI was confirmed by H&E and MHC staining. CONCLUSIONS: Data showed that tumor cytoablation using MRI-monitored LITT was possible in preclinical glioma models. Real-time MRI monitoring facilitated visualizing and controlling the area of ablation as it is otherwise performed in clinical applications.

Challenges Conveying Clinical Equipoise and Exploring Patient Treatment Preferences in an Oncology Trial Comparing Active Monitoring with Radiotherapy (ROAM/EORTC 1308).

INTRODUCTION: Providing balanced information that emphasizes clinical equipoise (i.e., uncertainty regarding the relative merits of trial interventions) and exploring patient treatment preferences can improve informed consent and trial recruitment. Within a trial comparing adjuvant radiotherapy versus active monitoring following surgical resection for an atypical meningioma (ROAM/EORTC-1308), we explored patterns in communication and reasons why health practitioners may find it challenging to convey equipoise and explore treatment preferences. MATERIALS AND METHODS: Qualitative study embedded within ROAM/EORTC-1308. Data were collected on 40 patients and 18 practitioners from 13 U.K. sites, including audio recordings of 39 patients' trial consultations, 23 patient interviews, and 18 practitioner interviews. Qualitative analysis drew on argumentation theory. RESULTS: Practitioners acknowledged the importance of the research question that the trial aimed to answer. However, they often demonstrated a lack of equipoise in consultations, particularly with eligible patients who practitioners believed to be susceptible to side effects (e.g., cognitive impairment) or inconvenienced by radiotherapy. Practitioners elicited but rarely explored patient treatment preferences, especially if a patient expressed an initial preference for active monitoring. Concerns about coercing patients, loss of practitioner agency, and time constraints influenced communication in ways that were loaded against trial participation. CONCLUSIONS: We identified several challenges that practitioners face in conveying equipoise and exploring patient treatment preferences in oncology, and particularly neuro-oncology, trials with distinct management pathways. The findings informed communication about ROAM/EORTC-1308 and will be relevant to enhancing trial communication in future oncology trials. Qualitative studies embedded within trials can address difficulties with communication, thus improving informed consent and recruitment. ROAM/EORTC-1308 RCT: ISRCTN71502099. IMPLICATIONS FOR PRACTICE: Oncology trials can be challenging to recruit to, especially those that compare treatment versus monitoring. Conveying clinical equipoise and exploring patient treatment preferences can enhance recruitment and patient understanding. This study focused on the challenges that practitioners encounter in trying to use such communication strategies and how practitioners may inadvertently impede patient recruitment and informed decision making. This article provides recommendations to support practitioners in balancing the content and presentation of trial management pathways. The results can inform training to optimize communication, especially for neuro-oncology trials and trials comparing markedly different management pathways.

Predictors of long-term anxiety and depression in uveal melanoma survivors: A cross-lagged five-year analysis.

OBJECTIVE: Cancer survivors commonly experience long-term anxiety and depression. Anxiety and depression might result from problems emerging during survivorship rather than illness and treatment. This study tested three potential causal paths: (a) concerns about physical symptoms and functional problems and fear of cancer recurrence (FCR) arising during survivorship directly cause anxiety and depression, (b) an indirect path whereby FCR mediates effects of concerns about physical symptoms and functional problems on anxiety and depression, and (c) a reciprocal path whereby anxiety and depression cause concerns about physical symptoms and functional problems and FCR, which exacerbate later anxiety and depression. METHODS: Sample of 453 uveal melanoma survivors who completed observations 6-, 12-, 24-, 36-, 48- and 60-months post-diagnosis and did not miss two consecutive observations. Cross-lagged analyses were conducted to predict Hospital Anxiety and Depression Scale subscale scores. Symptoms and functional problems were measured using the EORTC OPT 30 scale, and FCR operationalised by the EORTC OPT 30 worry about recurrence scale. Covariates were age, gender, treatment modality, and visual acuity of the fellow eye and chromosome-3 status (which accurately predicts 10-year survival), worry and anxiety or depression. RESULTS: All paths received some support, although the indirect path emerged only for anxiety in females. Concerns about physical symptoms, functional problems, and FCR originated in survivorship and appeared to both influence and be influenced by anxiety and depression. CONCLUSIONS: Findings emphasise the importance of actively monitoring survivors to prevent, detect, and intervene in the development of anxiety and depression during survivorship.

Could worry and rumination mediate relationships between self-compassion and psychological distress in breast cancer survivors?

Many breast cancer (BCa) patients experience clinically significant anxiety and depression in survivorship. Self-compassion offers a bulwark to anxiety and depression in nonclinical, mental health, and some chronic physical health populations. We examined whether self-compassion predicted lower anxiety and depression symptoms in survivors and whether this might be mediated by lower worry and rumination. The design was a cross-sectional survey using self-report measures. Female adult BCa survivors of mixed stages who had finished primary surgical, radiotherapy, or chemotherapy treatments completed self-compassion subscales and worry, rumination, and anxiety and depression scales. Higher self-compassion subscale scores were negatively associated with anxiety and depression. Depressive brooding and worry mediated any effects of self-kindness and mindfulness on depression and anxiety, whereas common humanity directly predicted lower depression scores. Findings are consistent with the view that self-compassion reduces threat-related rumination and worry in BCa survivors, consequently reducing anxiety and depression. This may form a basis for prevention and treatment.

Reconciling the theory and reality of shared decision-making: A "matching" approach to practitioner leadership.

Shared decision making (SDM) evolved to resolve tension between patients' entitlement to make health-care decisions and practitioners' responsibility to protect patients' interests. Implicitly assuming that patients are willing and able to make "good" decisions, SDM proponents suggest that patients and practitioners negotiate decisions. In practice, patients often do not wish to participate in decisions, or cannot make good decisions. Consequently, practitioners sometimes lead decision making, but doing so risks the paternalism that SDM is intended to avoid. We argue that practitioners should take leadership when patients cannot make good decisions, but practitioners will need to know: (a) when good decisions are not being made; and (b) how to intervene appropriately and proportionately when patients cannot make good decisions. Regarding (a), patients rarely make decisions using formal decision logic, but rely on informal propositions about risks and benefits. As propositions are idiographic and their meanings context-dependent, normative standards of decision quality cannot be imposed. Practitioners must assess decision quality by making subjective and contextualized judgements as to the "reasonableness" of the underlying propositions. Regarding (b), matched to judgements of reasonableness, we describe levels of leadership distinguished according to how directively practitioners act; ranging from prompting patients to question unreasonable propositions or consider new propositions, to directive leadership whereby practitioners recommend options or deny requested procedures. In the context of ideas of relational autonomy, the objective of practitioner leadership is to protect patients' autonomy by supporting good decision making, taking leadership in patients' interests only when patients are unwilling or unable to make good decisions.

Toward a noninvasive estimate of interstitial fluid pressure by dynamic contrast-enhanced MRI in a rat model of cerebral tumor.

PURPOSE: This study demonstrates a DCE-MRI estimate of tumor interstitial fluid pressure (TIFP) and hydraulic conductivity in a rat model of glioblastoma, with validation against an invasive wick-in-needle (WIN) technique. An elevated TIFP is considered a mark of aggressiveness, and a decreased TIFP a predictor of response to therapy. METHODS: The DCE-MRI studies were conducted in 36 athymic rats (controls and posttreatment animals) with implanted U251 cerebral tumors, and with TIFP measured using a WIN method. Using a model selection paradigm and a novel application of Patlak and Logan plots to DCE-MRI data, the MRI parameters required for estimating TIFP noninvasively were estimated. Two models, a fluid-mechanical model and a multivariate empirical model, were used for estimating TIFP, as verified against WIN-TIFP. RESULTS: Using DCE-MRI, the mean estimated hydraulic conductivity (MRI-K) in U251 tumors was (2.3 ± 3.1) × 10-5 (mm2 /mmHg-s) in control studies. Significant positive correlations were found between WIN-TIFP and MRI-TIFP in both mechanical and empirical models. For instance, in the control group of the fluid-mechanical model, MRI-TIFP was a strong predictor of WIN-TIFP (R2 = 0.76, p < .0001). A similar result was found in the bevacizumab-treated group of the empirical model (R2 = 0.93, p = .014). CONCLUSION: This research suggests that MRI dynamic studies contain enough information to noninvasively estimate TIFP in this, and possibly other, tumor models, and thus might be used to assess tumor aggressiveness and response to therapy.

Predictors of anxiety and depression 2 years following treatment in uveal melanoma survivors.

OBJECTIVE: We examined the role of posttreatment symptoms and functional problems and of worry about recurrent disease (WREC) in predicting probable anxiety and depression cases 24 months after diagnosis in survivors of posterior uveal melanoma. We examined whether WREC mediates links between symptoms, functional problems, and probable anxiety and depression cases. METHODS: Prospective cohort study of 261 treated uveal melanoma survivors 6, 12, and 24 months after diagnosis. Hierarchical logistic regression analyses predicting anxiety and depression 24 months after diagnosis identified by Hospital Anxiety and Depression Scale cutoff scores. Symptoms, functional problems, and WREC 6-month posttreatment were entered into the analyses as predictors, then the same variables at 12 months. We controlled anxiety or depression at 6 and 12 months and chromosome 3 status, which accurately predicts 10-year survival. Mediation of links between 6-month symptoms and functional problems and 24-month anxiety and depression by 12-month WREC was tested. RESULTS: Anxiety caseness at 24 months was predicted by 6-month ocular irritation, headache, and functional problems and 12-month WREC. Depression caseness at 24 months was predicted by 6-month headache and functional problems. Worry about recurrent disease at 12 months mediated prediction of anxiety caseness by 6-month symptoms and functional problems. Chromosome 3 status predicted neither anxiety nor depression. CONCLUSIONS: Survivors reporting symptoms, functional problems, and WREC should be monitored for anxiety and depression. Appropriate reassurance that symptoms do not signify future disease might help prevent anxiety.

How do women at increased breast cancer risk perceive and decide between risks of cancer and risk-reducing treatments? A synthesis of qualitative research.

OBJECTIVE: Risk-reducing procedures can be offered to people at increased cancer risk, but many procedures can have iatrogenic effects. People therefore need to weigh risks associated with both cancer and the risk-reduction procedure in their decisions. By reviewing relevant literature on breast cancer (BC) risk reduction, we aimed to understand how women at relatively high risk of BC perceive their risk and how their risk perceptions influence their decisions about risk reduction. METHODS: Synthesis of 15 qualitative studies obtained from systematic searches of SCOPUS, Web of Knowledge, PsychINFO, and Medline electronic databases (inception-June 2015). RESULTS: Women did not think about risk probabilistically. Instead, they allocated themselves to broad risk categories, typically influenced by their own or familial experiences of BC. In deciding about risk-reduction procedures, some women reported weighing the risks and benefits, but papers did not describe how they did so. For many women, however, an overriding wish to reduce intense worry about BC led them to choose aggressive risk-reducing procedures without such deliberation. CONCLUSIONS: Reasoning that categorisation is a fundamental aspect of risk perception, we argue that patients can be encouraged to develop more nuanced and accurate categorisations of their own risk through their interactions with clinicians. Empirically-based ethical reflection is required to determine whether and when it is appropriate to provide risk-reduction procedures to alleviate worry.

Phantom Eye Syndrome: Patient Experiences after Enucleation for Uveal Melanoma.

PURPOSE: Patients undergoing enucleation for uveal melanoma need to be informed of the possibility of phantom eye syndrome (PES). The number with uveal melanoma in PES studies has been small. Aims were to: (1) determine the prevalence, symptoms, and characteristics of PES and to test associations of PES symptoms with sociodemographic and clinical characteristics; (2) examine the interrelatedness of PES symptoms; and (3) explore the emotional valence of PES and the relationship to anxiety and depression. DESIGN: Cross-sectional questionnaire. PARTICIPANTS: Patients (n = 179) with uveal melanoma enucleated 4 to 52 months previously. METHODS: Questionnaire on PES. Responses to a routine audit of mood obtained from clinical records. MAIN OUTCOME MEASURES: Patients were asked about 3 symptoms: pain, visual sensations, and a feeling of seeing through the removed eye. Mood was assessed by the Hospital Anxiety and Depression Scale. RESULTS: Of 179 respondents, 108 (60.3%) experienced symptoms: 86 reported (48%) visual sensations, 50 reported (28%) seeing, and 42 reported (23%) pain; 14 (7.8%) reported all 3 symptoms. At the time of the questionnaire, 31 (17%) experienced 1 or more symptoms daily. Women were more likely to report pain (odds ratio [OR], 2.18; 95% confidence interval [CI], 1.08-4.40). Younger patients at enucleation were more likely to report pain (t = 4.13; degrees of freedom (df), 177; P < 0.001) and visual sensations (t = 2.11; df, 177; P < 0.05). Patients studied sooner after enucleation were more likely to report seeing (Mann-Whitney U, 2343; P < 0.05). Pain and seeing were intercorrelated (chi-square, 5.47; Φ = 0.18; df, 1; P < 0.05), pain with visual sensations (chi-square, 3.91; Φ = 0.15; df, 1; P < 0.05) and seeing with visual sensations (chi-square, 34.22; Φ = 0.45; df, 1; P < 0.001). Twenty of 108 patients (18.5%) found symptoms disturbing, and 21 of 108 (19.4%) pleasurable. Patients reporting pain were more anxious (OR, 3.53; 95% CI, 1.38-9.03) and depressed (OR, 13.26; 95% CI, 3.87-46.21). CONCLUSIONS: Patients should be informed of PES symptoms. Pain may indicate anxiety or depression; this needs research to determine cause and effect.

Peritumoral tissue compression is predictive of exudate flux in a rat model of cerebral tumor: an MRI study in an embedded tumor.

MRI estimates of extracellular volume and tumor exudate flux in peritumoral tissue are demonstrated in an experimental model of cerebral tumor. Peritumoral extracellular volume predicted the tumor exudate flux. Eighteen RNU athymic rats were inoculated intracerebrally with U251MG tumor cells and studied with dynamic contrast enhanced MRI (DCE-MRI) approximately 18 days post implantation. Using a model selection paradigm and a novel application of Patlak and Logan plots to DCE-MRI data, the distribution volume (i.e. tissue porosity) in the leaky rim of the tumor and that in the tissue external to the rim (the outer rim) were estimated, as was the tumor exudate flow from the inner rim of the tumor through the outer rim. Distribution volume in the outer rim was approximately half that of the inner adjacent region (p < 1 × 10(-4)). The distribution volume of the outer ring was significantly correlated (R(2) = 0.9) with tumor exudate flow from the inner rim. Thus, peritumoral extracellular volume predicted the rate of tumor exudate flux. One explanation for these data is that perfusion, i.e. the delivery of blood to the tumor, was regulated by the compression of the mostly normal tissue of the tumor rim, and that the tumor exudate flow was limited by tumor perfusion.

How do patients with uveal melanoma experience and manage uncertainty? A qualitative study.

OBJECTIVES: Cancer survivors experience uncertainty about the future, which can be distressing. A prognostication tool is available for uveal melanoma survivors, which can provide accurate estimates of life expectancy - a key source of uncertainty. Accurate prognostic information has not previously been available for healthy cancer survivors. The aims of this study were to identify how patients experience prognostic information and how it affects their experience of uncertainty. METHODS: Semi-structured interviews were conducted with 25 healthy survivors of uveal melanoma 6-60 months after treatment (approximately 8-62 months after receiving prognostic information). Data were analysed qualitatively. RESULTS: Patients did not feel that the prognostic information relieved uncertainty, which still overshadowed their lives. Different prognoses engendered different experiences of uncertainty. Those receiving poor life expectancy estimates reported uncertainties regarding the timing and form of metastases that they were likely to experience, but they also used uncertainty to justify feeling hopeful. Those receiving good prognoses were often unable wholly to accept these. Patients whose test results failed or were intermediate retained their original uncertainties. Patients managed their uncertainties by suppressing thoughts about them and by trusting in the care of clinicians and the health-care system. CONCLUSIONS: Uncertainty in the context of uveal melanoma is a complex and multifaceted experience that is not easily resolved by prognostication. Additional approaches are needed to help patients with the uncertainty that persists despite prognostication.

What does the public know about environmental health? A qualitative approach to refining an environmental health awareness instrument.

Despite an increased level of interest in environmental health concerns among the American public, awareness of the risks associated with environmental hazards is generally lacking. Assessing population awareness is typically performed through surveys, yet a comprehensive national environmental health questionnaire is currently unavailable. In 2009, a Delphi study using environmental health experts from federal, state, and local government and academia identified 11 core areas of environmental health (air, water, radiation, food safety, emergency preparedness, healthy housing, infectious disease and vector control, toxicology, injury prevention, waste and sanitation, and weather and climate change) and provided content validity for 443 questions covering 25 specific topics for possible inclusion on a national instrument. The authors' study described in this article used the qualitative approach of focus groups to refine the questions. Questions were divided into four sections and randomly assigned to a focus group location; 32 individuals participated. Results indicated that many perceptions are based on misinformation (or lack of information), which may lead to poor environmental health decision making.

Dynamic contrast enhanced MRI parameters and tumor cellularity in a rat model of cerebral glioma at 7 T.

PURPOSE: To test the hypothesis that a noninvasive dynamic contrast enhanced MRI (DCE-MRI) derived interstitial volume fraction (ve ) and/or distribution volume (VD ) were correlated with tumor cellularity in cerebral tumor. METHODS: T1 -weighted DCE-MRI studies were performed in 18 athymic rats implanted with U251 xenografts. After DCE-MRI, sectioned brain tissues were stained with Hematoxylin and Eosin for cell counting. Using a Standard Model analysis and Logan graphical plot, DCE-MRI image sets during and after the injection of a gadolinium contrast agent were used to estimate the parameters plasma volume (vp ), forward transfer constant (K(trans) ), ve , and VD . RESULTS: Parameter values in regions where the standard model was selected as the best model were: (mean ± S.D.): vp = (0.81 ± 0.40)%, K(trans) = (2.09 ± 0.65) × 10(-2) min(-1) , ve = (6.65 ± 1.86)%, and VD = (7.21 ± 1.98)%. The Logan-estimated VD was strongly correlated with the standard model's vp + ve (r = 0.91, P < 0.001). The parameters, ve and/or VD , were significantly correlated with tumor cellularity (r ≥ -0.75, P < 0.001 for both). CONCLUSION: These data suggest that tumor cellularity can be estimated noninvasively by DCE-MRI, thus supporting its utility in assessing tumor pathophysiology.

Intratumor distribution and test-retest comparisons of physiological parameters quantified by dynamic contrast-enhanced MRI in rat U251 glioma.

The distribution of dynamic contrast-enhanced MRI (DCE-MRI) parametric estimates in a rat U251 glioma model was analyzed. Using Magnevist as contrast agent (CA), 17 nude rats implanted with U251 cerebral glioma were studied by DCE-MRI twice in a 24 h interval. A data-driven analysis selected one of three models to estimate either (1) plasma volume (vp), (2) vp and forward volume transfer constant (K(trans)) or (3) vp, K(trans) and interstitial volume fraction (ve), constituting Models 1, 2 and 3, respectively. CA distribution volume (VD) was estimated in Model 3 regions by Logan plots. Regions of interest (ROIs) were selected by model. In the Model 3 ROI, descriptors of parameter distributions--mean, median, variance and skewness--were calculated and compared between the two time points for repeatability. All distributions of parametric estimates in Model 3 ROIs were positively skewed. Test-retest differences between population summaries for any parameter were not significant (p ≥ 0.10; Wilcoxon signed-rank and paired t tests). These and similar measures of parametric distribution and test-retest variance from other tumor models can be used to inform the choice of biomarkers that best summarize tumor status and treatment effects.