A placebo-controlled Bayesian dose finding design based on continuous reassessment method with application to stroke research.
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ABSTRACT:
SUBMITTER: Cai C
PROVIDER: S-EPMC5650116 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:A major practical impediment when implementing adaptive dose-finding designs is that the toxicity outcome used by the decision rules may not be observed shortly after the initiation of the treatment. To address this issue, we propose the data augmentation continual re-assessment method (DA-CRM) for dose finding. By naturally treating the unobserved toxicities as missing data, we show that such missing data are nonignorable in the sense that the missingness depends on the unobserved outcomes. The Bayesian data augmentation approach is used to sample both the missing data and model parameters from their posterior full conditional distributions. We evaluate the performance of the DA-CRM through extensive simulation studies, and also compare it with other existing methods. The results show that the proposed design satisfactorily resolves the issues related to late-onset toxicities and possesses desirable operating characteristics: treating patients more safely, and also selecting the maximum tolerated dose with a higher probability. The new DA-CRM is illustrated with two phase I cancer clinical trials.
| S-EPMC3972824 | biostudies-literature
Project description:IntroductionThe continual reassessment method (CRM) is a model-based design for phase I trials, which aims to find the maximum tolerated dose (MTD) of a new therapy. The CRM has been shown to be more accurate in targeting the MTD than traditional rule-based approaches such as the 3 + 3 design, which is used in most phase I trials. Furthermore, the CRM has been shown to assign more trial participants at or close to the MTD than the 3 + 3 design. However, the CRM's uptake in clinical research has been incredibly slow, putting trial participants, drug development and patients at risk. Barriers to increasing the use of the CRM have been identified, most notably a lack of knowledge amongst clinicians and statisticians on how to apply new designs in practice. No recent tutorial, guidelines, or recommendations for clinicians on conducting dose-finding studies using the CRM are available. Furthermore, practical resources to support clinicians considering the CRM for their trials are scarce.MethodsTo help overcome these barriers, we present a structured framework for designing a dose-finding study using the CRM. We give recommendations for key design parameters and advise on conducting pre-trial simulation work to tailor the design to a specific trial. We provide practical tools to support clinicians and statisticians, including software recommendations, and template text and tables that can be edited and inserted into a trial protocol. We also give guidance on how to conduct and report dose-finding studies using the CRM.ResultsAn initial set of design recommendations are provided to kick-start the design process. To complement these and the additional resources, we describe two published dose-finding trials that used the CRM. We discuss their designs, how they were conducted and analysed, and compare them to what would have happened under a 3 + 3 design.ConclusionsThe framework and resources we provide are aimed at clinicians and statisticians new to the CRM design. Provision of key resources in this contemporary guidance paper will hopefully improve the uptake of the CRM in phase I dose-finding trials.
| S-EPMC6339349 | biostudies-literature
Project description:An extensive literature has covered the statistical properties of the Continual Reassessment Method (CRM) and the modifications of this method. While there are some applications of CRM designs in recent Phase I trials, the standard method (SM) of escalating doses after three patients with an option for an additional three patients SM remains very popular, mainly due to its simplicity. From a practical perspective, clinicians are interested in designs that can estimate the MTD using fewer patients for a fixed number of doses, or can test more dose levels for a given sample size.This article compares CRM-based methods with the SM in terms of the number of patients needed to reach the MTD, total sample size required, and trial duration.The comparisons are performed under two alternative schemes: a fixed or a varying sample approach with the implementation of a stopping rule. The stopping rule halts the trial if the confidence interval around the MTD is within a pre-specified bound. Our simulations evaluated several CRM-based methods under different scenarios by varying the number of dose levels from five to eight and the location of the true MTD.CRM and SM are comparable in terms of how fast they reach the MTD and the total sample size required when testing a limited number of dose levels (<or=5), but as the number of dose levels increases, CRM reaches the MTD in fewer patients when used with a fixed sample of 20 patients. However, a sample size of 20-25 patients is not sufficient to achieve a narrow precision around the estimated toxicity rate at the MTD.We focused on methods with practical design features that are of interest to clinicians. However, there are several alternative CRM-based designs that are not investigated in this manuscript, and hence our results are not generalizable to other designs.We show that CRM-based methods are an improvement over the SM in terms of accuracy and optimal dose allocation in almost all cases, except when the true dose is among the lower levels.
| S-EPMC2637378 | biostudies-literature
Project description:BackgroundThis article studies the notion of irrational dose assignment in Phase I clinical trials. This property was recently defined by Zhou and colleagues as a dose assignment that fails to de-escalate the dose when two out of three, three out of six, or four out of six patients have experienced a dose-limiting toxicity event at the current dose level. The authors claimed that a drawback of the well-known continual reassessment method is that it can result in irrational dose assignments. The aim of this article is to examine this definition of irrationality more closely within the conduct of the continual reassessment method.MethodsOver a broad range of assumed dose-limiting toxicity probability scenarios for six study dose levels and a variety of target dose-limiting toxicity rates, we simulated 2000 trials of n = 36 patients. For each scenario, we counted the number of irrational dose assignments that were made by the continual reassessment method, according to the definitions of Zhou and colleagues. For each of the irrational decisions made, we classified the dose assignment as an underdose assignment, a target dose assignment, or an overdose assignment based on the true dose-limiting toxicity probability at that dose.ResultsAcross eight dose-toxicity scenarios, there were a total of 181,581 dose assignments made in the simulation study. Of these assignments, 8165 (4.5%) decisions were made when two out of three, three out of six, or four out of six patients had experienced a dose-limiting toxicity at the current dose. Of these 8165 decisions, 1505 (18.4%) recommended staying at the current dose level and would therefore be classified as irrational by Zhou and colleagues. Among the irrational decisions, 41.2% were misclassified, meaning they were made either at the true target dose (17.9%) or at a true underdose (23.3%). The remaining 58.8% were made at a true overdose and therefore truly irrational. Overall, irrational dose assignments comprised <1% of the total dose assignments made during the simulation study. Similar findings are reported in simulations across 100 randomly generated dose-toxicity scenarios from a recently proposed family of curves.ConclusionZhou and colleagues argue that the behavior of the continual reassessment method is disturbing due to its ability to make irrational dose assignments. These definitions are based on rules that mimic the popular 3 + 3 design, which should not be the benchmark used to construct guidelines for trial conduct of modern Phase I methods. Our study illustrates that these dose assignments occur very seldom in the continual reassessment method and that even when they do occur, they can often be considered sensible when accounting for all accumulated data in the study.
| S-EPMC6904537 | biostudies-literature
Project description:BackgroundScheduled cesarean section is routinely performed under spinal anesthesia using hyperbaric bupivacaine. The current study was undertaken to determine the clinically relevant 95% effective dose of intrathecal 2% hyperbaric prilocaine co-administered with sufentanil for scheduled cesarean section, using continual reassessment method.MethodsWe conducted a dose-response, prospective, double-blinded study to determine the ED95 values of intrathecal hyperbaric prilocaine used with 2,5 mcg of sufentanil and 100 mcg of morphine for cesarean delivery. Each parturient enrolled in the study received an intrathecal dose of hyperbaric prilocaine determined by the CRM and the success or failure of the block was assessed as being the primary endpoint.ResultsThe doses given for each cohort varied from 35 to 50?mg of HP, according to the CRM, with a final ED95 lying between 45 and 50?mg of Prilocaine after completion of the 10 cohorts. Few side effects were reported and patients were globally satisfied.ConclusionsThe ED95 of intrathecal hyperbaric prilocaine with sufentanil 2.5??g and morphine 100??g for elective cesarean delivery was found to be between 45 and 50?mg. It may be an interesting alternative to other long-lasting local anesthetics in this context.Trial registrationThe study was registered on January 30, 2017 - retrospectively registered - and results posted at the public database clinicaltrials.gov ( NCT03036384 ).
| S-EPMC7690017 | biostudies-literature
Project description:In most models and algorithms for dose-finding clinical trials, it is assumed that the trial participants are homogeneous-the optimal dose is the same for all those who qualify for the trial. However, if there are heterogeneous populations who may benefit from the same treatment, it is inefficient to conduct dose-finding separately for each group, and assuming homogeneity across all subpopulations may lead to identification of the incorrect dose for some (or all) subgroups. To accommodate heterogeneity in dose-finding trials when both efficacy and toxicity outcomes must be used to identify the optimal dose (as in immunotherapeutic oncology treatments), we utilize an adaptive Bayesian clustering method which borrows strength among similar subgroups and clusters truly homogeneous subgroups. Unlike methodology already described in the literature, our proposed methodology does not require the assumption of exchangeability between subgroups or a priori ordering of subgroups, but does allow for specification of different subgroup-specific priors if prior information is available. We provide a comparison of operating characteristics between our method and Bayesian hierarchical models for subgroups in a variety of relevant scenarios. After simulation studies with four a priori subgroups, we observed that our method and the hierarchical models both outperform separate subgroup-specific models when all subgroups have the same dose-efficacy and dose-toxicity curves. However, our method outperforms hierarchical models when one subgroup has a different dose-efficacy or dose-toxicity curve from the other three subgroups.
| S-EPMC9324955 | biostudies-literature
Project description:Treating patients with novel biological agents is becoming a leading trend in oncology. Unlike cytotoxic agents, for which efficacy and toxicity monotonically increase with dose, biological agents may exhibit non-monotonic patterns in their dose-response relationships. Using a trial with two biological agents as an example, we propose a dose-finding design to identify the biologically optimal dose combination (BODC), which is defined as the dose combination of the two agents with the highest efficacy and tolerable toxicity. A change-point model is used to reflect the fact that the dose-toxicity surface of the combinational agents may plateau at higher dose levels, and a flexible logistic model is proposed to accommodate the possible non-monotonic pattern for the dose-efficacy relationship. During the trial, we continuously update the posterior estimates of toxicity and efficacy and assign patients to the most appropriate dose combination. We propose a novel dose-finding algorithm to encourage sufficient exploration of untried dose combinations in the two-dimensional space. Extensive simulation studies show that the proposed design has desirable operating characteristics in identifying the BODC under various patterns of dose-toxicity and dose-efficacy relationships.
| S-EPMC3913186 | biostudies-literature
Project description:A novel subcutaneous allergen immunotherapy formulation (gpASIT+™) containing Lolium perenne peptides (LPP) and having a short up-dosing phase has been developed to treat grass pollen-induced seasonal allergic rhinoconjunctivitis. We investigated peptide immunotherapy containing the hydrolysate from perennial ryegrass allergens for the optimum dose in terms of clinical efficacy, immunogenicity and safety.This prospective, double-blind, placebo-controlled, phase IIb, parallel, four-arm, dose-finding study randomized 198 grass pollen-allergic adults to receive placebo or cumulative doses of 70, 170 or 370 ?g LPP. All patients received weekly subcutaneous injections, with the active treatment groups reaching assigned doses within 2, 3 and 4 weeks, respectively. Efficacy was assessed by comparing conjunctival provocation test (CPT) reactions at baseline, after 4 weeks and after completion. Grass pollen-specific immunoglobulins were analysed before and after treatment.Conjunctival provocation test (CPT) response thresholds improved from baseline to V7 by at least one concentration step in 51.2% (170 ?g; P = .023), 46.3% (370 ?g), and 38.6% (70 ?g) of patients receiving LPP vs 25.6% of patients receiving placebo (modified per-protocol set). Also, 39% of patients in the 170-?g group became nonreactive to CPT vs 18% in the placebo group. Facilitated allergen-binding assays revealed a highly significant (P < .001) dose-dependent reduction in IgE allergen binding across all treatment groups (70 ?g: 17.1%; 170 ?g: 18.8%; 370 ?g: 26.4%). Specific IgG4 levels increased to 1.6-fold (70 ?g), 3.1-fold (170 ?g) and 3.9-fold (370 ?g) (mPP).Three-week immunotherapy with 170 ?g LPP reduced CPT reactivity significantly and increased protective specific antibodies.
| S-EPMC5947135 | biostudies-other
Project description:The overall aim was to investigate the effects of low and high dose vitamin D supplementation on genome-wide gene expression and how this is modulated by genetic variation. We adopted a functional genomics approach to analyse study participants in the BEST-D clinical trial (placebo, low dose or high dose supplementation over a 12-month treatment period).
2018-04-21 | E-MTAB-6246 | biostudies-arrayexpress
Project description:We propose a flexible design for the identification of optimal dose combinations in dual-agent dose finding clinical trials. The design is called AAA, standing for three adaptations: adaptive model selection, adaptive dose insertion and adaptive cohort division. The adaptations highlight the need and opportunity for innovation for dual-agent dose finding and are supported by the numerical results presented in the proposed simulation studies. To our knowledge, this is the first design that allows for all three adaptations at the same time. We find that AAA enhances the chance of finding the optimal dose combinations and shortens the trial duration. A clinical trial is being planned to apply the AAA design and a Web tool is being developed for both statisticians and non-statisticians.
| S-EPMC6561465 | biostudies-literature