Machine Learning Methods in Health Economics and Outcomes Research-The PALISADE Checklist: A Good Practices Report of an ISPOR Task Force.

Advances in machine learning (ML) and artificial intelligence offer tremendous potential benefits to patients. Predictive analytics using ML are already widely used in healthcare operations and care delivery, but how can ML be used for health economics and outcomes research (HEOR)? To answer this question, ISPOR established an emerging good practices task force for the application of ML in HEOR. The task force identified 5 methodological areas where ML could enhance HEOR: (1) cohort selection, identifying samples with greater specificity with respect to inclusion criteria; (2) identification of independent predictors and covariates of health outcomes; (3) predictive analytics of health outcomes, including those that are high cost or life threatening; (4) causal inference through methods, such as targeted maximum likelihood estimation or double-debiased estimation-helping to produce reliable evidence more quickly; and (5) application of ML to the development of economic models to reduce structural, parameter, and sampling uncertainty in cost-effectiveness analysis. Overall, ML facilitates HEOR through the meaningful and efficient analysis of big data. Nevertheless, a lack of transparency on how ML methods deliver solutions to feature selection and predictive analytics, especially in unsupervised circumstances, increases risk to providers and other decision makers in using ML results. To examine whether ML offers a useful and transparent solution to healthcare analytics, the task force developed the PALISADE Checklist. It is a guide for balancing the many potential applications of ML with the need for transparency in methods development and findings.

Semiparametric estimation of the cure fraction in population-based cancer survival analysis.

With rapid development in medical research, the treatment of diseases including cancer has progressed dramatically and those survivors may die from causes other than the one under study, especially among elderly patients. Motivated by the Surveillance, Epidemiology, and End Results (SEER) female breast cancer study, background mortality is incorporated into the mixture cure proportional hazards (MCPH) model to improve the cure fraction estimation in population-based cancer studies. Here, that patients are "cured" is defined as when the mortality rate of the individuals in diseased group returns to the same level as that expected in the general population, where the population level mortality is presented by the mortality table of the United States. The semiparametric estimation method based on the EM algorithm for the MCPH model with background mortality (MCPH+BM) is further developed and validated via comprehensive simulation studies. Real data analysis shows that the proposed semiparametric MCPH+BM model may provide more accurate estimation in population-level cancer study.

Excitotoxicity downregulates TrkB.FL signaling and upregulates the neuroprotective truncated TrkB receptors in cultured hippocampal and striatal neurons.

Brain-derived neurotrophic factor (BDNF) plays an important role in neuronal survival through activation of TrkB receptors. The trkB gene encodes a full-length receptor tyrosine kinase (TrkB.FL) and its truncated (T1/T2) isoforms. We investigated the changes in TrkB protein levels and signaling activity under excitotoxic conditions, which are characteristic of brain ischemia, traumatic brain injury, and neurodegenerative disorders. Excitotoxic stimulation of cultured rat hippocampal or striatal neurons downregulated TrkB.FL and upregulated a truncated form of the receptor (TrkB.T). Downregulation of TrkB.FL was mediated by calpains, whereas the increase in TrkB.T protein levels required transcription and translation activities. Downregulation of TrkB.FL receptors in hippocampal neurons correlated with a decrease in BDNF-induced activation of the Ras/ERK and PLCγ pathways. However, calpain inhibition, which prevents TrkB.FL degradation, did not preclude the decrease in signaling activity of these receptors. On the other hand, incubation with anisomycin, to prevent the upregulation of TrkB.T, protected to a large extent the TrkB.FL signaling activity, suggesting that truncated receptors may act as dominant-negatives. The upregulation of TrkB.T under excitotoxic conditions was correlated with an increase in BDNF-induced inhibition of RhoA, a mediator of excitotoxic neuronal death. BDNF fully protected hippocampal neurons transduced with TrkB.T when present during excitotoxic stimulation with glutamate, in contrast with the partial protection observed in cells overexpressing TrkB.FL or expressing GFP. These results indicate that BDNF protects hippocampal neurons by two distinct mechanisms: through the neurotrophic effects of TrkB.FL receptors and by activation of TrkB.T receptors coupled to inhibition of the excitotoxic signaling.

The Amblyopia Quality of Life (AmbQoL): Development and Content Validation of a Novel Health-Related Quality of Life Instrument for Use in Adult and Pediatric Amblyopia Populations.

INTRODUCTION: Amblyopia is a neurodevelopmental vision disorder, characterized by poor vision in one or both eyes. Given the lack of existing clinical outcome assessments (COA) considered fit-for-purpose for amblyopia clinical trials, this study developed new COAs to assess amblyopia symptoms and health-related quality of life (HRQoL) impacts in adult and pediatric amblyopia populations that conform with best practice standards and regulatory guidelines. METHODS: Findings from a targeted qualitative literature review informed the development of three versions of the new Amblyopia Quality of Life Questionnaire (AmbQoL): a patient-reported outcome measure (PRO) for individuals aged 13 years and older, a PRO for children aged 9-12 years, and an observer-reported outcome measure (ObsRO) for caregivers of children aged 4-8 years. Qualitative interviews were conducted with the target populations, and with ophthalmologists experienced in treating amblyopia patients to evaluate the content validity for further development of the AmbQoL. A translatability assessment was conducted to ensure cultural appropriateness and usability across multiple languages. Feedback from Food and Drug Administration (FDA) was also sought on the instruments, and clinical experts provided input at key stages. RESULTS: Interviews were conducted with 112 patients/caregivers and ten ophthalmologists from the USA, France, and Germany. The instructions, items, and response options were well understood across all AmbQoL versions. Feedback from the patients, caregivers, ophthalmologists, the translatability assessment, the FDA, and the expert clinicians informed minor wording modifications to enhance clarity and translatability. Some items were removed due to low relevance. The study resulted in a 23-item adult/adolescent PRO, 24-item child PRO, and 12-item ObsRO, each employing a 7-day recall period. CONCLUSION: Each AmbQoL version has documented support for its face and content validity for use in amblyopia populations aged ≥ 4 years. Further research is necessary to evaluate the psychometric measurement properties of the AmbQoL instruments to enable their use in amblyopia treatment trials.

Qualitative Exploration of the Visual Function Impairments and Health-Related Quality of Life Impacts of Amblyopia in Adult and Pediatric Populations.

INTRODUCTION: Amblyopia is a reduction in vision in one or both eyes due to impaired development of the visual pathway. This study explored the experience of amblyopia and treatment from the patient, caregiver, and clinician perspectives. METHODS: A targeted literature review, including a review of social media listening (SML) studies, was conducted. Next, qualitative interviews were conducted with amblyopia patients, caregivers of children with amblyopia, and ophthalmologists with experience treating patients with amblyopia. The findings informed the development of a disease model. Amblyopia clinical experts provided input at key stages. RESULTS: Twelve data sources were reviewed, including qualitative studies in the literature and SML studies. Overall, 133 patients/caregivers were interviewed (23 adults, 16 adolescents, 47 child-caregiver dyads), plus 10 ophthalmologists from the United States, France, and Germany. Reduced visual acuity, impaired depth perception, impaired peripheral vision, and double vision were the most frequently reported symptoms. Amblyopia impacted daily activities (reading, using digital devices), the ability to move around, school/work (productivity, seeing the board in class), emotional well-being (frustration, sadness), and social functioning (difficulty socializing). Treatments, including patching and corrective lens, also impacted daily activities (using digital devices, sports/leisure), mobility (bumping into things), and work/school (tasks taking longer) as well as emotional well-being (embarrassment), and social functioning (bullying/stigma). CONCLUSION: The findings contribute valuable insights into the adult and pediatric experience of amblyopia from a multi-stakeholder perspective. The findings were used to critically assess existing clinical outcome assessments and supported the development of patient- and observer-reported outcome measures for use in amblyopia clinical trials.

Efficacy and Safety of Brolucizumab, Aflibercept, and Ranibizumab for the Treatment of Patients with Visual Impairment Due to Diabetic Macular Oedema: A Systematic Review and Network Meta-Analysis.

INTRODUCTION: Key clinical guidelines recommend anti-vascular endothelial growth factor (VEGF) therapy as first-line treatment for visual impairment due to diabetic macular oedema (DMO). A systematic literature review (SLR) and network meta-analysis (NMA) were conducted comparing the relative efficacy of the anti-VEGF brolucizumab with a focused network of the most relevant comparator dosing regimens approved in countries other than the USA (aflibercept, ranibizumab). The safety and tolerability of brolucizumab were also assessed. METHODS: A broad SLR was conducted to identify randomised controlled trials to ensure all relevant potential comparators were captured. Identified studies were refined to those appropriate for inclusion in the NMA. A Bayesian NMA was conducted comparing brolucizumab 6 mg (every 12 [Q12W]/every 8 weeks [Q8W]) with relevant aflibercept 2 mg and ranibizumab 0.5 mg regimens. RESULTS: Fourteen studies were included in the NMA. At 1-year follow-up, the various aflibercept 2 mg and ranibizumab 0.5 mg regimens were mostly comparable with brolucizumab 6 mg Q12W/Q8W across key visual and anatomical outcomes, except brolucizumab 6 mg was favoured over ranibizumab 0.5 mg every 4 weeks (Q4W) for the change from baseline (CFB) in best-corrected visual acuity (BCVA), and BCVA loss/gain of pre-specified numbers of letters, and over ranibizumab 0.5 mg pro re nata for CFB in diabetic retinopathy severity scale, and retinal thickness. At year 2, where data were available, brolucizumab 6 mg showed similar results across efficacy outcomes versus all other anti-VEGFs. In most cases, discontinuation rates (all cause, and due to adverse events [AE]) and serious and overall rates of AEs excluding ocular inflammatory events were similar (in unpooled and pooled-treatment analyses) versus comparators. CONCLUSION: Brolucizumab 6 mg Q12W/Q8W was comparable or superior to aflibercept 2 mg and ranibizumab 0.5 mg regimens for various visual and anatomical efficacy outcomes and discontinuation rates.

A Social Media Listening Study to Understand the Unmet Needs and Quality of Life in Adult and Pediatric Amblyopia Patients.

INTRODUCTION: Amblyopia is an important cause of monocular vision impairment worldwide, and it negatively impacts patients' quality of life (QoL). Understanding patients' perspectives may help to optimize treatment outcomes and improve treatment adherence. METHODS: This was a non-interventional, retrospective analysis of social media data available in the public domain posted by patients and caregivers on selected social media channels (Twitter®, forums, blogs, and news) from 12 countries between July 2018 and June 2020. RESULTS: Approximately 2662 conversations relevant to the research objective were analyzed. The patient journey for adults and children was constructed based on the conversations. Eyeglasses, eye patches, contact lenses, and vision exercises were the common treatment options for amblyopia. Patients also reported vision improvement with emerging technologies such as digital therapeutics. Amblyopia and its treatment had a negative impact on QoL, and increased caregiver burden. Insurance coverage, long appointment waiting times, and recurring expenses of treatment options were reported as barriers to treatment. Non-compliance, switching between treatment options or technology, or discontinuation of treatment options was found to emanate from various issues including no improvement of the condition, discomfort with the treatment option, bullying, dissatisfaction with healthcare professional (HCP) recommendation, cost of treatment/issues with insurance coverage, side effects, and/or other unspecified reasons. The need for regular eye examinations, better diagnostic tests, awareness of the disease, awareness amongst HCPs about treatment options, and the need for better health insurance coverage policies emerged as unmet needs. CONCLUSION: This social media listening study generated insights on patients with amblyopia and their caregivers regarding the patient journey, treatment options, reasons for non-compliance, reasons for switching HCPs, barriers to treatment, and unmet needs. Further qualitative research is required to validate the findings.

Mixture Cure Models in Oncology: A Tutorial and Practical Guidance.

Novel cancer therapies are associated with survival patterns that differ from established therapies, which may include survival curves that plateau after a certain follow-up time point. A fraction of the patient population is then considered statistically cured and subject to the same mortality experience as the cancer-free general population. Mixture cure models have been developed to account for this characteristic. As compared to standard survival analysis, mixture cure models can often lead to profoundly different estimates of long-term survival, required for health economic evaluations. This tutorial is designed as a practical introduction to mixture cure models. Step-by-step instructions are provided for the entire implementation workflow, i.e., from gathering and combining data from different sources to fitting models using maximum likelihood estimation and model results interpretation. Two mixture cure models were developed to illustrate (1) an "uninformed" approach where the cure fraction is estimated from trial data and (2) an "informed" approach where the cure fraction is obtained from an external source (e.g., real-world data) used as an input to the model. These models were implemented in the statistical software R, with the freely available code on GitHub. The cure fraction can be estimated as an output from ("uninformed" approach) or used as an input to ("informed" approach) a mixture cure model. Mixture cure models suggest presumed estimates of long-term survival proportions, especially in instances where some fraction of patients is expected to be statistically cured. While this type of model may initially seem complex, it is straightforward to use and interpret. Mixture cure models have the potential to improve the accuracy of survival estimates for treatments associated with statistical cure, and the present tutorial outlines the interpretation and implementation of mixture cure models in R. This type of model will likely become more widely used in health economic analyses as novel cancer therapies enter the market.

Cost-effectiveness of obinutuzumab versus rituximab biosimilars for previously untreated follicular lymphoma.

BACKGROUND: In the randomized phase 3 GALLIUM trial, first-line treatment with obinutuzumab (GA101; G) plus chemotherapy (G + chemo) resulted in superior progression-free survival (PFS) compared with rituximab plus chemotherapy (R + chemo) for patients with follicular lymphoma (FL). G + chemo was found to be cost-effective when compared with R + chemo (incremental cost-effectiveness ratio [ICER] of approximately $2,300 per quality-adjusted life-year [QALY] gained). Two rituximab biosimilars, rituximab-abbs (Ra) and rituximab-pvvr (Rp), have been approved by the FDA for use in this setting. However, the cost-effectiveness of G + chemo versus Ra + chemo and Rp + chemo has not yet been estimated. OBJECTIVE: To evaluate the cost-effectiveness of G + chemo versus Ra + chemo and Rp + chemo in the first-line treatment of FL. METHODS: We adapted an existing Markov model that compared G + chemo with R + chemo, using investigator-assessed PFS and postprogression survival data from the GALLIUM trial to model overall survival. All patients in the study received induction chemoimmunotherapy with either G + chemo or R + chemo, with responders then receiving obinutuzumab or rituximab maintenance therapy for 2 years or until disease progression. We assumed that the efficacy and safety of the rituximab biosimilars plus chemotherapy were the same as the R + chemo arm of the GALLIUM study. Drug utilization and treatment duration were also derived from GALLIUM. Health care costs were based on Medicare reimbursements, and drug costs were average sale prices for intravenous therapies or wholesale acquisition costs for oral therapies used after progression. Utility estimates were based on the GALLIUM trial data and published literature. Sensitivity analyses were conducted to assess the key drivers of the model and uncertainty in the results. Results: Treatment with G + chemo led to an increase of 0.93 QALYs relative to rituximab biosimilars plus chemotherapy (95% credible range [CR] = 0.36-1.46). The total cost of G + chemo was $191,317, whereas the total costs of Ra + chemo and Rp + chemo were $164,340 (Δ14.1%) and $169,755 (Δ11.3%), respectively, with G + chemo resulting in incremental costs of $26,978 (95% CR = $19,781-$33,119) and $21,562 (95% CR = $14,473-$28,389), respectively. The incremental total drug and administration costs were $32,678 (Δ25.4%) and $27,263 (Δ21.2%) for G + chemo versus Ra + chemo and G + chemo versus Rp + chemo, respectively. There were cost savings of $7,050 (Δ-12.4%) related to disease progression for G + chemo ($56,727) compared with Ra + chemo and Rp + chemo ($63,777). ICERs were $28,879 and $23,082 per QALY gained for G + chemo versus Ra + chemo and Rp + chemo, respectively. In probabilistic sensitivity analyses, G + chemo was cost-effective at the $50,000 and $100,000 per QALY thresholds versus both Ra + chemo (88% and 98% probabilities of cost-effectiveness, respectively) and Rp + chemo (93% and 98%, respectively). CONCLUSIONS: G + chemo is projected to be cost-effective versus rituximab biosimilars plus chemotherapy in the United States as first-line treatment for FL, driven by increased QALYs for G + chemo and cost savings from delayed disease progression. DISCLOSURES: This study was funded by Genentech, a member of the Roche Group. The study sponsor was involved in study design, data interpretation, and writing of the report. All authors approved the decision to submit the report for publication. Spencer and Guzauskas report fees from Genentech during the conduct of the study. Felizzi was employed by F. Hoffmann-La Roche at the time this study was conducted; Launonen is an employees of F. Hoffmann-La Roche. Felizzi and Launonen previously had share ownership in Novartis. Dawson and Masaquel are employees of Genentech, and they have stock options in F. Hoffmann-La Roche. Veenstra reports fees from Genentech, during the conduct of this study and outside of the submitted work. This work was presented, in part, at the AACR Virtual Meeting Advances in Malignant Lymphoma meeting (virtual; August 17-19, 2020) and the SOHO annual meeting (virtual; September 9-12, 2020).

Cost-effectiveness of atezolizumab versus docetaxel and nivolumab in the treatment of non-small cell lung cancer as a second line in France.

Aim: To estimate the cost-effectiveness of atezolizumab compared with docetaxel and nivolumab for the treatment of advanced non-small cell lung cancer (NSCLC), as a second-line treatment, in a French setting.Materials and methods: A three-state partitioned-survival model was developed (progression-free survival, post-progression survival, death) based on the phase IIIOAK trial on a 10-year time horizon. The comparison between nivolumab and atezolizumab came from a network meta-analysis. Utilities were estimated from the OAK trial EQ-5D applying the French utility tariffs. Overall survival (OS), progression-free survival (PFS), and treatment duration were estimated using parametric models selected using Akaike and Bayesian information criterion. Extrapolation beyond the trial duration followed NICE DSU TSD 14. Economic perspective was the one of all payers, discount rate fixed at 4% on benefits and costs. This analysis was aligned with French Haute Autorité de Santé recommendations. Results were expressed in total cost (2019) and €/QALY (Quality Adjusted Life Year). Model robustness was checked through sensitivity analyses, and a probabilistic sensitivity analysis was conducted.Results: In comparison to docetaxel, atezolizumab costs 49,429€ more and increased life expectancy by 8 months, generating 0.47 QALY. Incremental cost-effectiveness ratio was estimated at 104,835€/QALY. When comparing nivolumab to atezolizumab, a cost minimization analysis was conducted since no clear evidence supporting a difference in terms of survival benefit was reported. Using list price, and the Market Access Authorization regimens, atezolizumab saved approximately 6,000€, 9.5% of its total costs. Sensitivity analyses confirmed the robustness of our findings.Conclusion: Atezolizumab is more efficient and more costly than docetaxel in the second-line treatment of NSCLC of stage IIIB or IV, in France, with results consistent to previous French authorities' evaluation of immunotherapies in similar indication. Lastly, atezolizumab is a cost saving alternative to nivolumab, based on list price.

US cost-effectiveness of polatuzumab vedotin, bendamustine and rituximab in diffuse large B-cell lymphoma.

Aim: To evaluate the cost-effectiveness of polatuzumab vedotin (pola) + bendamustine + rituximab (BR) in relapsed/refractory diffuse large B-cell lymphoma based on the GO29365 trial from a US payer's perspective. Materials & methods: A partitioned survival model used progression-free survival and overall survival data from the GO29365 trial. The base case analysis assumed overall survival was informed by progression-free survival; a mixture cure model estimated proportion of long-term survivors. Results: In the base case, pola + BR was cost-effective versus BR at US$35,864 per quality-adjusted life year gained. Probabilistic and one-way sensitivity analyses showed that the findings were robust. Conclusion: Pola + BR is cost-effective versus BR for the treatment of transplant-ineligible relapsed/refractory diffuse large B-cell lymphoma in the US.

Cost-effectiveness of second-line atezolizumab in Canada for advanced non-small cell lung cancer (NSCLC).

Aim: To assess the cost-effectiveness in Canada of atezolizumab compared with docetaxel or nivolumab for the treatment of advanced NSCLC after first-line platinum-doublet chemotherapy. Materials and methods: A three-state partitioned-survival model was developed. Clinical inputs were obtained from the phase III OAK trial comparing atezolizumab with docetaxel in patients with advanced NSCLC who progressed after first-line platinum-doublet chemotherapy. Overall survival (OS) and progression-free survival (PFS) were extrapolated beyond the trial period using parametric models. A cure model assuming a 1% cure fraction was fitted to the OS data for atezolizumab. Outcomes for nivolumab were informed by a network meta-analysis (NMA) vs atezolizumab. Resource use and costs were informed by clinical expert opinion and published Canadian sources. Utility values were obtained from the OAK trial. The perspective of the analysis was that of the Canadian publicly-funded healthcare system. The base case time horizon was 10 years, and the discount rate was 1.5% annually for both costs and effects. Scenario analyses were performed to test the robustness of the results and all analyses were performed probabilistically. Results: Atezolizumab demonstrated a quality-adjusted life-year (QALY) gain of 0.60 compared with docetaxel at an incremental cost of $85,073, resulting in an incremental cost-effectiveness ratio (ICER) of $142,074/QALY. Atezolizumab dominated nivolumab (regardless of dosing regimen), based on modest differences in both QALYs and costs. Docetaxel was most likely to be cost effective at willingness-to-pay (WTP) thresholds below $125,000/QALY gained, while atezolizumab was most likely to be cost effective beyond this WTP threshold. In most scenario analyses, the results remained robust to changes in parameters. A reduced time horizon and alternative approaches to the NMA had the greatest impact on cost-effectiveness results. Conclusion: Atezolizumab represents a cost-effective therapeutic option in Canada for the treatment of patients with advanced NSCLC who progress after first-line platinum doublet chemotherapy.

Patient-Reported Outcomes in OAK: A Phase III Study of Atezolizumab Versus Docetaxel in Advanced Non-Small-cell Lung Cancer.

BACKGROUND: The randomized phase III OAK (a study of atezolizumab compared with docetaxel in participants with locally advanced or metastatic non-small-cell lung cancer [NSCLC] who have failed platinum-containing therapy) trial investigated the anti-programmed cell death ligand 1 (PD-L1) antibody atezolizumab for advanced or metastatic, previously treated, NSCLC. Atezolizumab significantly improved overall survival (OS) compared with docetaxel (hazard ratio [HR], 0.73; 95% confidence interval [CI], 0.62-0.87; P = .0003; median OS, 13.8 vs. 9.6 months, respectively). Patient-reported outcomes (PROs) were collected to evaluate disease-related symptoms and health-related quality of life (HRQoL) to support the finding of a survival benefit. PATIENTS AND METHODS: The first 850 patients were randomized to receive atezolizumab (1200 mg every 3 weeks) or docetaxel (75 mg/m2 every 3 weeks). PROs were collected on day 1 of cycle 1, day 1 of every subsequent cycle, and at the end-of-treatment visit for patients who completed ≥ 1 baseline and 1 postbaseline PRO assessment. The European Organisation for the Research and Treatment of Cancer QoL questionnaire and lung cancer module were used to assess PROs. RESULTS: Atezolizumab delayed the time to deterioration (TTD) in physical function (HR, 0.75; 95% CI, 0.58-0.98) and role function (HR, 0.79; 95% CI, 0.62-1.00) and numerically improved patients' HRQoL from baseline compared with docetaxel. Atezolizumab also prolonged the TTD in chest pain (HR, 0.71; 95% CI, 0.49-1.05; P = .0823), although both arms showed an objective reduction relative to baseline. Overall, the patients had no clinically significant worsening in treatment-related symptoms, although the scores favored atezolizumab. CONCLUSION: These PRO data support the clinical benefit of atezolizumab in patients with previously treated advanced or metastatic NSCLC. Atezolizumab prolonged the TTD of patients' limitations in role and physical functions compared with docetaxel.

Updated Efficacy Analysis Including Secondary Population Results for OAK: A Randomized Phase III Study of Atezolizumab versus Docetaxel in Patients with Previously Treated Advanced Non-Small Cell Lung Cancer.

INTRODUCTION: The efficacy and safety of atezolizumab versus the efficacy and safety of docetaxel as second- or third-line treatment in patients with advanced NSCLC in the primary (n = 850) and secondary (n = 1225) efficacy populations of the randomized phase III OAK study (respectively referred to as the intention-to-treat [ITT] 850 [ITT850] and ITT1225) at an updated data cutoff were assessed. METHODS: Patients received atezolizumab, 1200 mg, or docetaxel, 75 mg/m2, intravenously every 3 weeks until loss of clinical benefit or disease progression, respectively. The primary end point was overall survival (OS) in the ITT population and programmed death-ligand 1-expressing subgroup. A sensitivity analysis was conducted to evaluate the impact of subsequent immunotherapy use in the docetaxel arm on the observed survival benefit with atezolizumab. RESULTS: Atezolizumab demonstrated an OS benefit versus docetaxel in the updated ITT850 (hazard ratio [HR] = 0.75, 95% confidence interval: 0.64-0.89, p = 0.0006) and the ITT1225 (HR = 0.80, 95% confidence interval: 0.70-0.92, p = 0.0012) after minimum follow-up times of 26 and 21 months, respectively. Improved survival with atezolizumab was observed across programmed death-ligand 1 and histological subgroups. In the immunotherapy sensitivity analysis, the relative OS benefit with atezolizumab was slightly greater in the ITT850 (HR = 0.69) and ITT1225 (HR = 0.74) than the conventional OS estimate. Fewer patients receiving atezolizumab experienced grade 3 or 4 treatment-related adverse events (14.9%) than did patients receiving docetaxel (42.4%); no grade 5 adverse events related to atezolizumab were observed. CONCLUSIONS: The results of the updated ITT850 and initial ITT1225 analyses were consistent with those of the primary efficacy analysis demonstrating survival benefit with atezolizumab versus with docetaxel. Atezolizumab continued to demonstrate a favorable safety profile after longer treatment exposure and follow-up.

Enhanced cellular sensitivity from partitioning the integrin receptors into multiple clusters.

Integrins are essential receptors for the development and functioning of multicellular organisms because they mediate cell adhesion and migration, and regulate cell proliferation and apoptosis. In response to cues in the extracellular matrix, they are observed to organize into many clusters. The number and size of such clusters are observed to vary according to the concentration of and affinity for the extracellular ligand. The realization of a cluster point pattern is governed by a doubly stochastic process, controlling the number of clusters and the number of points per cluster. We construct entropy measures for the separation of two doubly stochastic processes and demonstrate how the self-organization of integrins in multiple clusters contributes to the accuracy in sensing the extracellular environment.

Network-of-queues approach to B-cell-receptor affinity discrimination.

The immune system is one of the most complex signal processing machineries in biology. The adaptive immune system, consisting of B and T lymphocytes, is activated in response to a large spectrum of pathogen antigens. B cells recognize and bind the antigen through B-cell receptors (BCRs) and this is fundamental for B-cell activation. However, the system response is dependent on BCR-antigen affinity values that span several orders of magnitude. Moreover, the ability of the BCR to discriminate between affinities at the high end (e.g., 10^{9}M^{-1}-10^{10}M^{-1}) challenges the formulation of a mathematical model able to robustly separate these affinity-dependent responses. Queuing theory enables the analysis of many related processes, such as those resulting from the stochasticity of protein binding and unbinding events. Here we define a network of queues, consisting of BCR early signaling states and transition rates related to the propensity of molecular aggregates to form or disassemble. By considering the family of marginal distributions of BCRs in a given signaling state, we report a significant separation (measured as Jensen-Shannon divergence) that arises from a broad spectrum of antigen affinities.

Analyzing and constraining signaling networks: parameter estimation for the user.

The behavior of most dynamical models not only depends on the wiring but also on the kind and strength of interactions which are reflected in the parameter values of the model. The predictive value of mathematical models therefore critically hinges on the quality of the parameter estimates. Constraining a dynamical model by an appropriate parameterization follows a 3-step process. In an initial step, it is important to evaluate the sensitivity of the parameters of the model with respect to the model output of interest. This analysis points at the identifiability of model parameters and can guide the design of experiments. In the second step, the actual fitting needs to be carried out. This step requires special care as, on the one hand, noisy as well as partial observations can corrupt the identification of system parameters. On the other hand, the solution of the dynamical system usually depends in a highly nonlinear fashion on its parameters and, as a consequence, parameter estimation procedures get easily trapped in local optima. Therefore any useful parameter estimation procedure has to be robust and efficient with respect to both challenges. In the final step, it is important to access the validity of the optimized model. A number of reviews have been published on the subject. A good, nontechnical overview is provided by Jaqaman and Danuser (Nat Rev Mol Cell Biol 7(11):813-819, 2006) and a classical introduction, focussing on the algorithmic side, is given in Press (Numerical recipes: The art of scientific computing, Cambridge University Press, 3rd edn., 2007, Chapters 10 and 15). We will focus on the practical issues related to parameter estimation and use a model of the TGFß-signaling pathway as an educative example. Corresponding parameter estimation software and models based on MATLAB code can be downloaded from the authors's web page ( http://www.bsse.ethz.ch/cobi ).