Evaluation of Randomized Discontinuation Design

Adaptive Enrichment Designs in Clinical Trials

Adaptive enrichment designs for clinical trials may include rules that use interim data to identify treatment-sensitive patient subgroups, select or compare treatments, or change entry criteria. A common setting is a trial to compare a new biologically targeted agent to standard therapy. An enrichment design's structure depends on its goals, how it accounts for patient heterogeneity and treatment effects, and practical constraints. This article first covers basic concepts, including treatment-biomarker interaction, precision medicine, selection bias, and sequentially adaptive decision making, and briefly describes some different types of enrichment. Numerical illustrations are provided for qualitatively different cases involving treatment-biomarker interactions. Reviews are given of adaptive signature designs; a Bayesian design that uses a random partition to identify treatment-sensitive biomarker subgroups and assign treatments; and designs that enrich superior treatment sample sizes overall or within subgroups, make subgroup-specific decisions, or include outcome-adaptive randomization.

PSA decay during salvage radiotherapy for prostate cancer as a predictor of disease outcome - 5 year follow-up of a prospective observational study

BACKGROUND AND PURPOSE

Biochemical recurrence after prostatectomy is commonly treated with salvage radiotherapy (SRT). In this prospective observational study we investigated the PSA decay rate, determined by predefined serial PSA measurements during SRT, as a predictor for treatment outcome.

MATERIALS AND METHODS

Between 2013 and 2016, 214 patients were included in the study. The prescribed dose to the prostate bed was 70 Gy in 35 fractions (7 weeks) without hormonal treatment. PSA was measured weekly during SRT. Assuming first order kinetics, a PSA decay-rate constant (k) was calculated for 196 eligible patients. The ability of k to predict disease progression was compared with known clinical prediction parameters using Cox regression, logistic regression and ROC analyses. Disease progression was defined as continuously rising PSA after SRT, PSA increase by ≥0.2 ng/ml above nadir after SRT, hormonal treatment or clinical progression.

RESULTS

After a median follow up of 4.7 years the estimated failure-free survival at 5 years was 56%. The PSA decay-rate constant (k) was found to be the strongest predictor of disease progression in both uni-and multivariable analyses.

CONCLUSION

The addition of k to established clinical variables significantly improves the possibility to predict treatment outcome after SRT and could be used to personalize future therapies.

A Review of Perspectives on the Use of Randomization in Phase II Oncology Trials

Historically, phase II oncology trials assessed a treatment's efficacy by examining its tumor response rate in a single-arm trial. Then, approximately 25 years ago, certain statistical and pharmacological considerations ignited a debate around whether randomized designs should be used instead. Here, based on an extensive literature review, we review the arguments on either side of this debate. In particular, we describe the numerous factors that relate to the reliance of single-arm trials on historical control data and detail the trial scenarios in which there was general agreement on preferential utilization of single-arm or randomized design frameworks, such as the use of single-arm designs when investigating treatments for rare cancers. We then summarize the latest figures on phase II oncology trial design, contrasting current design choices against historical recommendations on best practice. Ultimately, we find several ways in which the design of recently completed phase II trials does not appear to align with said recommendations. For example, despite advice to the contrary, only 66.2% of the assessed trials that employed progression-free survival as a primary or coprimary outcome used a randomized comparative design. In addition, we identify that just 28.2% of the considered randomized comparative trials came to a positive conclusion as opposed to 72.7% of the single-arm trials. We conclude by describing a selection of important issues influencing contemporary design, framing this discourse in light of current trends in phase II, such as the increased use of biomarkers and recent interest in novel adaptive designs.

Treatment Recommendations Should Take Account of Individual Patient Variation Not Just Group Responses

Recommendations for treatment are commonly based on results evaluating variation in systematic effects (group responses) from randomised controlled trials without taking the individual patient's variation into account. In the evaluation of acupuncture-related treatment effects, the trial design and statistical analysis used are a challenge since the assessed variables commonly have subjective properties and are based on the person's own self-report. Thus, the results that are seen are often varied, most likely due to inter-individual variation in rating of the actual variable such that the treatment effects are expressed more (or less) in some individuals than in others. The basis for the individual variation is probably multi-modal and could be related to the individuals’ expectation, gender, genetic polymorphisms and the aetiology of the condition. The assessment methods used should preferably have proven useful in controlled trials, and the methods for statistical analysis should consider the non-metric properties of the variable and the contribution of the individuals’ variation in the results. In order to evaluate the treatment effects more properly and increase the possibility of detecting any effectiveness, it is therefore important to assess the level of perceived dysfunction or symptom, taking into account the individual variation as well as the systematic effects (the effects of the group). In the evaluation of acupuncture effects, both systematic and individual variation should be reported allowing for the detection of subgroup effects and thereby leading to treatment recommendations that are more likely to be based on each individual's specific needs.

Circulating vascular endothelial growth factor (VEGF) as predictive factor of progression-free survival in patients with advanced chordoma receiving sorafenib: an analysis from a phase II trial of the french sarcoma group (GSF/GETO)

Background

Patients with advanced chordoma are often treated with tyrosine kinase inhibitors without any predictive factor to guide decision. We report herein an ancillary analysis of the the Angionext phase II trial (NCT 00874874).

Results

From May 2011 to January 2014, 26 were sampled. The 9-month PFS rate was 72.9% (95%-CI: 45.9-87.9). During sorafenib treatment, a significant increase in PlGF (18.4 vs 43.8 pg/mL, p<0.001) was noted along with a non-significant increase in VEGF (0.7 vs 1.0 ng/mL, p=0.07). VEGF at D1 >1.04 ng/mL (HR=12.5, 95%-CI: 1.37-114, p=0.025) and VEGF at D7 >1.36 ng/mL (HR=10.7, 95%-CI: 1.16-98, p=0.037) were associated with shorter PFS. The 9-month PFS rate was 92.3% (95%-CI: 56.6-98.9) when VEGF at D1 was ≤1.04 ng/mL versus 23.3% (95%-CI: 1.0-63.2) when >1.04 ng/mL.

Patients and Methods

Chordoma patients were treated with sorafenib 800 mg/day for 9 months, unless earlier occurrence of progression or toxicities. Six biomarkers (sE-Selectin, VEGF, VEGF-C, placental growth factor (PlGF), Thrombospondin, Stem Cell Factor (SCF)) were measured at baseline (day 1: D1) and day 7 (D7).

Conclusion

High levels of VEGF was associated with poor outcome.

Maintenance efficacy designs in psychiatry: Randomized discontinuation trials - enriched but not better

Introduction

Although classical randomized clinical trials (RCTs) are the gold standard for proof of drug efficacy, randomized discontinuation trials (RDTs), sometimes called “enriched” trials, are used increasingly, especially in psychiatric maintenance studies.

Methods

A narrative review of two decades of experience with RDTs.

Results

RDTs in psychiatric maintenance trials tend to use a dependent variable as a predictor: treatment response. Treatment responders are assessed for treatment response. This tautology in the logic of RDTs renders them invalid, since the predictor and the outcome are the same variable. Although RDTs can be designed to avoid this tautologous state of affairs, like using independent predictors of outcomes, such is not the case with psychiatric maintenance studies

Further, purported benefits of RDTs regarding feasibility were found to be questionable. Specifically, RDTs do not enhance statistical power in many settings, and, because of high dropout rates, produce results of questionable validity. Any claimed benefits come with notably reduced generalizability.

Conclusions

RDTs appear to be scientifically invalid as used in psychiatric maintenance designs. Their purported feasibility benefits are not seen in actual trials for psychotropic drugs. There is warrant for changes in federal policy regarding marketing indications for maintenance efficacy using the RDT design.

Advanced chordoma treated by first-line molecular targeted therapies: Outcomes and prognostic factors. A retrospective study of the French Sarcoma Group (GSF/GETO) and the Association des Neuro-Oncologues d'Expression Française (ANOCEF)

BACKGROUND

To assess the role of first-line Molecular Targeted Therapies (MTTs) in Advanced chordoma (AC) patients.

METHODS

Retrospective study of 80 patients treated between January 2004 and December 2015 at 15 major French Sarcoma or Neurooncology Centres.

RESULTS

The sex ratio M/F was 46/34. The median age was 59 (6-86) years. The primary sites were the sacrum (50, 62.5%), mobile spine (12, 15.0%), and skull base (18, 22.5%). Metastases were present in 28 patients (36.0%). The first line of MTTs consisted of imatinib (62, 77.5%), sorafenib (11, 13.7%), erlotinib (5, 6.3%), sunitinib (1, 1.2%) and temsirolimus (1, 1.2%). The reported responses were: partial response (5, 6.3%), stable disease (58, 72.5%), or progressive disease (10, 12.5%). Symptomatic improvement was seen in 28/66 assessable patients (42.4%) and was associated with an objective response occurrence (p = 0.005), imatinib (p = 0.020) or erlotinib use (p = 0.028). The median progression-free survival (PFS) was 9.4°months (95% CI, [6.8-16.1]). Two independent factors of poor prognosis for PFS were identified: a skull-based primary location (HR = 2.5, p = 0.019), and the interval between diagnosis and MTT of <52months (HR = 2.8, p < 0.001). The median overall survival (OS) was 4.4°years (95% CI, [3.8-5.6]). Four independent factors of poor prognosis for OS were identified: the presence of liver metastases (HR = 13.2, p < 0.001), pain requiring opioids (HR = 2.9, p = 0.012), skull-based primary location (HR = 19.7, p < 0.001), and prior radiotherapy (photon alone) (HR = 2.5, p = 0.024). The PFS and OS did not significantly differ between the MTT.

CONCLUSIONS

The prognostic factors identified require validation in an independent database but are potently useful to guide treatment decisions and design further clinical trials.

Adaptive Clinical Trials: Overview of Phase III Designs and Challenges

Adaptive designs use accruing data to make changes in an ongoing trial according to a prespecified plan and potentially offer great efficiencies for clinical development. There are many types of adaptive designs and many trial aspects that could in theory be adapted. However, the scope of adaptive designs with relevance in confirmatory trials is narrower, and in addition, extensive pre-planning is needed and various types of challenges need to be addressed in order to use these designs in this stage of development. Nevertheless, with careful planning, there are opportunities for these designs to offer important benefits even in the confirmatory stage of development. We provide an overview of adaptive designs that have relevance for confirmatory trials and discuss considerations that may affect whether they should or should not be used in particular trials or programs as well as the challenges that need to be addressed.

Phase 2 study of sorafenib in malignant mesothelioma previously treated with platinum-containing chemotherapy

INTRODUCTION

The incidence of mesothelioma is rising. First-line cisplatin and pemetrexed confers a survival benefit, with a median progression-free survival (PFS) of 5.7 months. Sorafenib inhibits tyrosine kinases, including receptors for vascular endothelial growth factor, which are implicated in mesothelioma pathogenesis by preclinical and clinical data.

METHODS

Sorafenib, at 400 mg twice daily, was assessed in a single-arm multicenter phase 2 study, using Simon's two-stage design. Eligible patients had received platinum combination chemotherapy earlier. The primary endpoint was PFS at 6 months, with secondary endpoints, including response rate and metabolic response, assessed using fluorodeoxyglucose positron emission tomography. Published reference values for PFS in mesothelioma provide a benchmark for the null hypothesis of 28% progression-free at 6 months, and for moderate or significant clinical activity of 35% or 43% progression-free at 6 months, respectively.

RESULTS

Fifty-three patients (72%) were treated. Most had epithelioid histology. Ninety-three percent of patients had a performance status 0 or 1. Treatment was well tolerated with few grade 3 or 4 toxicities. Median PFS was 5.1 months, with 36% of patients being progression-free at 6 months. Nine percent of patients remained on study beyond 1 year. Changes in fluorodeoxyglucose positron emission tomography parameters did not predict clinical outcome.

CONCLUSIONS

Sorafenib is well tolerated in patients with mesothelioma after completion of platinum-containing chemotherapy. PFS of sorafenib compares favorably with that reported for other targeted agents, and suggests moderate activity in this disease.

Run-in phase III trial design with pharmacodynamics predictive biomarkers

BACKGROUND

Developments in biotechnology have stimulated the use of predictive biomarkers to identify patients who are likely to benefit from a targeted therapy. Several randomized phase III designs have been introduced for development of a targeted therapy using a diagnostic test. Most such designs require biomarkers measured before treatment. In many cases, it has been very difficult to identify such biomarkers. Promising candidate biomarkers can sometimes be effectively measured after a short run-in period on the new treatment.

METHODS

We introduce a new design for phase III trials with a candidate predictive pharmacodynamic biomarker measured after a short run-in period. Depending on the therapy and the biomarker performance, the trial would either randomize all patients but perform a separate analysis on the biomarker-positive patients or only randomize marker-positive patients after the run-in period. We evaluate the proposed design compared with the conventional phase III design and discuss how to design a run-in trial based on phase II studies.

RESULTS

The proposed design achieves a major sample size reduction compared with the conventional randomized phase III design in many cases when the biomarker has good sensitivity (≥0.7) and specificity (≥0.7). This requires that the biomarker be measured accurately and be indicative of drug activity. However, the proposed design loses some of its advantage when the proportion of potential responders is large (>50%) or the effect on survival from run-in period is substantial.

CONCLUSIONS

Incorporating a pharmacodynamic biomarker requires careful consideration but can expand the capacity of clinical trials to personalize treatment decisions and enhance therapeutics development.

Estimation of Progression-Free Survival for All Treated Patients in the Randomized Discontinuation Trial Design

The randomized discontinuation trial (RDT) design is an enrichment-type design that has been used in a variety of diseases to evaluate the efficacy of new treatments. The RDT design seeks to select a more homogeneous group of patients, consisting of those who are more likely to show a treatment benefit if one exists. In oncology, the RDT design has been applied to evaluate the effects of cytostatic agents, that is, drugs that act primarily by slowing tumor growth rather than shrinking tumors. In the RDT design, all patients receive treatment during an initial, open-label run-in period of duration T. Patients with objective response (substantial tumor shrinkage) remain on therapy while those with early progressive disease are removed from the trial. Patients with stable disease (SD) are then randomized to either continue active treatment or switched to placebo. The main analysis compares outcomes, for example, progression-free survival (PFS), between the two randomized arms. As a secondary objective, investigators may seek to estimate PFS for all treated patients, measured from the time of entry into the study, by combining information from the run-in and post run-in periods. For t ≤ T, PFS is estimated by the observed proportion of patients who are progression-free among all patients enrolled. For t > T, the estimate can be expressed as Ŝ(t) = p̂_OR × Ŝ_OR(t - T) + p̂_SD × Ŝ_SD(t - T), where p̂_OR is the estimated probability of response during the run-in period, p̂_SD is the estimated probability of SD, and Ŝ_OR(t - T) and Ŝ_SD(t - T) are the Kaplan-Meier estimates of subsequent PFS in the responders and patients with SD randomized to continue treatment, respectively. In this article, we derive the variance of Ŝ(t), enabling the construction of confidence intervals for both S(t) and the median survival time. Simulation results indicate that the method provides accurate coverage rates. An interesting aspect of the design is that outcomes during the run-in phase have a negative multinomial distribution, something not frequently encountered in practice.

Adaptive trial designs: a review of barriers and opportunities

Adaptive designs allow planned modifications based on data accumulating within a study. The promise of greater flexibility and efficiency stimulates increasing interest in adaptive designs from clinical, academic, and regulatory parties. When adaptive designs are used properly, efficiencies can include a smaller sample size, a more efficient treatment development process, and an increased chance of correctly answering the clinical question of interest. However, improper adaptations can lead to biased studies. A broad definition of adaptive designs allows for countless variations, which creates confusion as to the statistical validity and practical feasibility of many designs. Determining properties of a particular adaptive design requires careful consideration of the scientific context and statistical assumptions. We first review several adaptive designs that garner the most current interest. We focus on the design principles and research issues that lead to particular designs being appealing or unappealing in particular applications. We separately discuss exploratory and confirmatory stage designs in order to account for the differences in regulatory concerns. We include adaptive seamless designs, which combine stages in a unified approach. We also highlight a number of applied areas, such as comparative effectiveness research, that would benefit from the use of adaptive designs. Finally, we describe a number of current barriers and provide initial suggestions for overcoming them in order to promote wider use of appropriate adaptive designs. Given the breadth of the coverage all mathematical and most implementation details are omitted for the sake of brevity. However, the interested reader will find that we provide current references to focused reviews and original theoretical sources which lead to details of the current state of the art in theory and practice.

Phase 2 trial design in neuro-oncology revisited: a report from the RANO group

Advances in the management of gliomas, including the approval of agents such as temozolomide and bevacizumab, have created an evolving therapeutic landscape in glioma treatment, thus affecting our ability to reliably use historical controls to comparatively assess the activity of new therapies. Furthermore, the increasing availability of novel, targeted agents--which are competing for a small patient population, in view of the low incidence of primary brain tumours--draws attention to the need to improve the efficiency of phase 2 clinical testing in neuro-oncology to expeditiously transition the most promising of these drugs or combinations to potentially practice-changing phase 3 trials. In this report from the Response Assessment in Neurooncology (RANO) group, we review phase 2 trial designs that can address these challenges and capitalise on scientific and clinical advances in brain tumour treatment in neuro-oncology to accelerate and optimise the selection of drugs deserving further testing in phase 3 trials. Although there is still a small role for single-arm and non-comparative phase 2 designs, emphasis is placed on the potential role that comparative randomised phase 2 designs--such as screening designs, selection designs, discontinuation designs, and adaptive designs, including seamless phase 2/3 designs--can have. The rational incorporation of these designs, as determined by the specific clinical setting and the trial's endpoints or goals, has the potential to substantially advance new drug development in neuro-oncology.

Propentofylline, a CNS glial modulator does not decrease pain in post-herpetic neuralgia patients: in vitro evidence for differential responses in human and rodent microglia and macrophages

There is a growing body of preclinical evidence for the potential involvement of glial cells in neuropathic pain conditions. Several glial-targeted agents are in development for the treatment of pain conditions. Here we report the failure of a glial modulating agent, propentofylline, to decrease pain reported in association with post-herpetic neuralgia. We offer new evidence to help explain why propentofylline failed in patients by describing in vitro functional differences between rodent and human microglia and macrophages. We directly compared the proinflammatory response induced by lipopolysaccharide (LPS) with or without propentofylline using rat postnatal microglia, rat peritoneal macrophages, human fetal microglia, human peripheral macrophages and human immortalized THP-1 cells. We measured tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β) and nitrite release (as an indicator of nitric oxide (NO)) as downstream indicators. We found that LPS treatment did not induce nitrite in human microglia, macrophages or THP-1 cells; however LPS treatment did induce nitrite release in rat microglia and macrophages. Following LPS exposure, propentofylline blocked TNF-α release in rodent microglia with all the doses tested (1-100 μM), and dose-dependently decreased TNF-α release in rodent macrophages. Propentofylline partially decreased TNF-α (35%) at 100 μM in human microglia, macrophages and THP-1 macrophages. Propentofylline blocked nitrite release from LPS stimulated rat microglia and inhibited nitrite in LPS-stimulated rat macrophages. IL-1β was decreased in LPS-stimulated human microglia following propentofylline at 100 μM. Overall, human microglia were less responsive to LPS stimulation and propentofylline treatment than the other cell types. Our data demonstrate significant functional differences between cell types and species following propentofylline treatment and LPS stimulation. These results may help explain the differential behavioral effects of propentofylline observed between rodent models of pain and the human clinical trial.

Bayesian enrichment strategies for randomized discontinuation trials

We propose optimal choice of the design parameters for random discontinuation designs (RDD) using a Bayesian decision-theoretic approach. We consider applications of RDDs to oncology phase II studies evaluating activity of cytostatic agents. The design consists of two stages. The preliminary open-label stage treats all patients with the new agent and identifies a possibly sensitive subpopulation. The subsequent second stage randomizes, treats, follows, and compares outcomes among patients in the identified subgroup, with randomization to either the new or a control treatment. Several tuning parameters characterize the design: the number of patients in the trial, the duration of the preliminary stage, and the duration of follow-up after randomization. We define a probability model for tumor growth, specify a suitable utility function, and develop a computational procedure for selecting the optimal tuning parameters.

Phase II clinical trials in oncology: are we hitting the target?

The number of novel and molecularly targeted agents in the last decade that need screening for preliminary efficacy in Phase II trials has increased. Many of these agents have a cytostatic mode of action that is difficult to assess using traditional Phase II designs. These new agents require detailed evaluation to optimize their dosing, to evaluate their effects on their target and to define early markers that predict for a definitive benefit. This review focuses on the options for Phase II trial designs. The different end points, single versus multiarm and randomized designs, the use of biomarkers and Bayesian approaches are also reviewed. The final design chosen will depend on the characteristics and circumstances of each individual study.

Other paradigms: randomized discontinuation trial design

Phase II oncologic clinical trials for agents that are mainly growth inhibitory and benefit only a selected patient population are challenging. The randomized discontinuation trial design is one approach by which this can be accomplished. A broad patient population is enrolled and all patients receive the investigational agent. Those with tumor shrinkage sufficient to be deemed of likely clinical significance after a prespecified period continue treatment, those with growth sufficient to be deemed clinically adverse and those with toxicity discontinue, and the remaining patients with "stable disease" are randomized to continue or discontinue therapy in a double-blind manner. The primary end point is the fraction of patients who remain progression free after an additional postrandomization period or the time to progression after randomization. By enriching for a possible sensitive population and then testing whether this was due to the agent or selection of an indolent disease group, the randomized discontinuation trial design efficiently assesses the putative growth inhibitory properties of an investigational agent and furthermore minimizes the number of patients exposed to placebo.

[Phases 0, 1 and 2 oncology clinical trials: current questions]

We propose here a general review of current questions related to early trials, including the choice of the primary endpoint, role of bayesian designs, role of stratification and randomization for phase 2 trials, patient selection, and new designs for phase 1 and phase 0 trials. We also discuss the difficulties to apply such methodologies to molecular targeted therapies development.

Sorafenib tosylate in advanced kidney cancer: past, present and future

The objective of this paper was to review the development of sorafenib tosylate in kidney cancer. The MedLine database, the Proceedings of the Annual American Society of Clinical Oncology meeting, as well as those of other key international meetings were extensively searched to identify relevant publications. Furthermore, the authors' direct experience with the drug was taken into account when commenting on the results retrieved. Sorafenib is a multikinase inhibitor that targets VEGF and PDGF receptors, other kinases, as well as the serine-threonine kinase Raf. Following early signs of activity from phase I and II studies, it has been shown to improve survival of pretreated advanced kidney cancer patients within a placebo-controlled, randomized, phase III trial, leading to its approval both in the United States and in Europe. Its activity has been subsequently confirmed in a real-world population by two expanded access programs performed globally, but not in a first-line setting; it also proved to be non-cross-resistant with two other molecularly targeted agents. Finally, its toxicity profile, which is acceptable and highly predictable, makes sorafenib appealing for combination treatments, especially with other molecularly targeted agents. Despite having been already demonstrated to be active in kidney cancer, the exact role of sorafenib in the first-line setting, in patients who have failed other molecularly targeted agents, and especially in combination with other agents, deserves further, prospective, studies.

Patient selection for phase II trials

The standard phase II trial design yields disparate results with similar regimens owing, in part, to variable patient populations enrolled, and appears to be a poor indicator of efficacy demonstrable in a phase III trial. While other phase II trial designs attempt to rectify this problem including the randomized phase II trial and randomized discontinuation trial, they demand more resources and a larger number of patients and are not definitive. A paradigm of multicenter straight phase II trials with rigorous attention to patient selection criteria to improve the validity and reproducibility of results is proposed. Such trials may be superior guides to select regimens for further development than trials that are single-center based with favorable populations.

Next generation oncology drug development: opportunities and challenges

The optimal development of novel molecularly targeted agents for the treatment of cancer requires a re-evaluation of the current drug development paradigm. Selection of patients, optimal biologic dose versus maximum tolerated dose, definition of response and clinical benefit and trial designs that address these considerations are the focus of debate in the field of early cancer therapeutics. We present a review of the opportunities and challenges facing drug development in oncology through the phases of clinical development starting with first-in-human trials.

Comparison of power between randomized discontinuation design and upfront randomization design on progression-free survival

PURPOSE

Enrichment based on molecular characteristics has emerged as an important inclusion criterion in phase II trials of targeted anticancer agents. In this study, we evaluate a well-described method of population enrichment by tumor growth characteristics in the early development stage of targeted cytostatic agents.

METHODS

For some solid tumors, such as pancreatic carcinoma, using a time-to-event end point (eg, time to disease progression) to evaluate the efficacy of a cytostatic agent in a phase II trial is more relevant than clinical response by Response Evaluation Criteria in Solid Tumors. In this setting, we compared the power of the randomized discontinuation and upfront randomization designs under two previously proposed tumor growth models for treatment effect when the end point is time-to-event.

RESULTS

By selecting patients with more homogeneous tumor growth characteristics, the randomized discontinuation design is more efficient than the upfront randomization design when treatment benefit is restricted to slow-growing tumors. Under a model where only a subset of patients expressing the molecular target are sensitive to the agent, the randomized discontinuation design is more powerful than the upfront randomization design when the treatment effect is small; and vice versa when the treatment effect is moderate to large.

CONCLUSION

For selected targeted agents where a bioassay to select patients expressing the specific molecular target is not available, the randomized discontinuation design is a feasible alternative patient enrichment strategy in certain disease settings and provides a reasonable platform to evaluate drugs before phase III testing.

Suggested response criteria for phase II antitumor drug studies for neurofibromatosis type 2 related vestibular schwannoma

Neurofibromatosis type 2 (NF2) is a tumor suppressor gene syndrome characterized by multiple schwannomas, especially vestibular schwannomas (VS), and meningiomas. Anticancer drug trials are now being explored, but there are no standardized endpoints in NF2. We review the challenges of NF2 clinical trials and suggest possible response criteria for use in initial phase II studies. We suggest two main response criteria in such trials. Objective radiographic response is defined as a durable 20% or greater reduction in VS volume based on post-contrast T1-weighted MRI images collected with 3 mm or finer cuts through the internal auditory canal. Hearing response is defined as a statistically significant improvement in word recognition scores using 50-word recorded lists in audiology. A possible composite endpoint incorporating both radiographic response and hearing response is outlined. We emphasize pitfalls in response assessment and suggest guidelines to minimize misinterpretations of response. We also identify research goals in NF2 to facilitate future trial conduct, such as identifying the expectations for time to tumor progression and time to measurable hearing loss in untreated NF2-related VS, and the relation of both endpoints to patient prognostic factors (such as age, baseline tumor volume, and measures of disease severity). These data would facilitate future use of endpoints based on stability of tumor size and hearing, which might be more appropriate for testing certain drugs. We encourage adoption of standardized endpoints early in the development of phase II trials for this population to facilitate comparison of results across trials of different agents.

Randomized phase II designs

As the use of molecularly targeted agents, which are anticipated to increase overall survival (OS)and progression-free survival (PFS) but not necessarily tumor response, has increased in oncology, there has been a corresponding increase in the recommendation and use of randomized phase II designs. Such designs reduce the potential for bias, existent in comparisons with historical controls, but also substantially increase the sample size requirements. We review the principal statistical designs for historically controlled and randomized phase II trials, along with their advantages, disadvantages, and statistical design considerations. We review the arguments for and against the use of randomization in phase II studies, the situations in which the use of historical controls is preferred, and the situations in which the use of randomized designs is preferred. We review methods used to calculate predicted OS or PFS values from historical controls, adjusted so as to be appropriate for an experimental sample with particular prognostic characteristics. We show how adjustment of the type I and type II error bounds for randomized studies can facilitate the detection of appropriate target increases in median PFS or OS with sample sizes appropriate for phase II studies. Although there continue to be differences among investigators concerning the use of randomization versus historical controls in phase II trials, there is agreement that each approach will continue to be appropriate, and the optimal approach will depend upon the circumstances of the individual trial.

Enriched enrollment: definition and effects of enrichment and dose in trials of pregabalin and gabapentin in neuropathic pain. A systematic review

AIMS

Enriched enrollment study designs have been suggested to be useful for proof of concept when only a proportion of the diseased population responds to a treatment intervention. We aim to investigate whether this really is the case in trials of pregabalin and gabapentin in neuropathic pain.

METHODS

We defined 'complete', 'partial' and 'non-enriched' enrollment, and examined pregabalin and gabapentin trials for the extent of enrichment and for effects of enrichment on efficacy and adverse event outcomes.

RESULTS

There were no studies using complete enriched enrollment; seven trials used partial enriched enrollment and 14 non-enriched enrollment. In pregabalin trials the maximum extent of enrichment was estimated at about 12%. Partial enriched enrollment did not change estimates of efficacy or harm. Over 150-600 mg maximum daily dose there was strong dose dependence for pregabalin.

CONCLUSIONS

A benefit of partial over non-enriched enrollment could not be demonstrated because the degree of enrichment was rather small, and possibly because enrichment produced little enhancement of treatment effect. Whether a greater degree of enrichment would result in important differences is unknown. Researchers reporting clinical trials with any enrichment must describe both process and extent of enrichment. As things stand, the effects of enriched enrollment remain unknown for neuropathic pain trials.

Methodology of clinical trials with new molecular-targeted agents: where do we stand?

In recent years, we have witnessed growing interest in the methodology of clinical trials with molecular-targeted agents. In phase I studies, alternative end points to toxicity have been proposed to define the optimal biological dose: the identification of a 'target effect', the measurement of 'surrogates' for biological activity and the assessment of drug plasma levels. However, these end points are not routinely incorporated into the study design and have rarely formed the primary basis for dose selection. In phase II studies, response rate remains the preferred end point in the early evaluation of new drugs. However, this approach might lead to rejection of potentially useful drugs when significant tumor shrinkage cannot be demonstrated. Therefore, a number of alternative end points have been proposed for agents that are not expected to cause a major tumor regression: time to progression, progression-free survival, overall survival, early progression rate and growth modulation index. In phase III trials, where efficacy in terms of survival remains the most important goal of the research, the major issues are the adequate selection of patients and the optimal clinical setting of evaluation of drugs. In conclusion, many important questions regarding the methodology of clinical research with target-based agents remain open and need to be defined by research in the near future.

Design and conduct of phase II studies of targeted anticancer therapy: recommendations from the task force on methodology for the development of innovative cancer therapies (MDICT)

The Methodology for the Development of Innovative Cancer Therapies (MDICT) task force considered aspects of the design and conduct of phase II studies for molecular targeted agents during their 2007 meeting. The task force recommended that multinomial endpoints and designs should be considered for phase II studies of targeted agents, that both single arm as well as randomised designs remain appropriate in certain settings, and that further assessment of novel endpoints (tumour growth kinetic assessment, biomarker or functional imaging) and designs (randomised discontinuation or Bayesian adaptive design) be encouraged. The MDICT cautioned on the use of small randomised trials which have a number of statistical pitfalls and dangers and strongly encouraged the complete reporting, including negative trials, in the scientific literature.

The randomized discontinuation trial: a phase II design to assess growth-inhibitory agents: Figure 1

An increasing number of putative anticancer targets and drugs have been identified with many of these expected to be growth inhibitory. Clinical development of these agents in the phase II setting is challenging because tumor shrinkages, or at least tumor shrinkages that meet the standard definitions of objective response, are not expected. Time to progression end points are however problematic because expected times in the absence of therapy (the null hypothesis) cannot be predicted accurately, thus requiring trials to enroll a concurrent control group. Another problem is that the patient population that will benefit from a new drug remains poorly defined in early-phase development. The randomized discontinuation trial design addresses both of these issues. All patients are initially treated with the drug; patients with an objective response continue therapy; patients who do not progress or experience excess toxicity within a prespecified "run-in" period are then randomized to continuing or discontinuing therapy in a double-blind, placebo controlled manner. Despite certain limitations that need to be recognized, the ability of this design to "select" a cohort most likely to benefit and to rigorously evaluate the disease-stabilizing activity of an investigational agent provides multiple advantages.

Tyrosine kinase inhibitors of vascular endothelial growth factor receptors in clinical trials: current status and future directions

Angiogenesis plays a central role in the process of tumor growth and metastatic dissemination. The vascular endothelial growth factor (VEGF) family of peptide growth factors and receptors are key regulators of this process. Agents directed either against VEGF or VEGF receptors (VEGFRs) have been developed. The tyrosine kinase inhibitors of VEGFRs are low-molecular-weight, ATP-mimetic proteins that bind to the ATP-binding catalytic site of the tyrosine kinase domain of VEG-FRs, resulting in blockade of intracellular signaling. Several of these agents are currently in different phases of clinical development. Large randomized phase III trials have demonstrated the efficacy of sunitinib and sorafenib in the treatment of patients affected by gastrointestinal stromal tumors and renal cancer refractory to standard therapies, respectively. Positive results also have been reported with the combination of ZD6474 and chemotherapy in previously treated non-small cell lung cancer patients. For other agents, such as vatalanib, contrasting outcomes in metastatic colorectal cancer patients have been reported: the final results of these trials are expected in 2006. However, several key questions remain to be addressed, regarding the choice of an adequate dose or schedule, the presence of "off-target" effects, the safety of long-term administration, and the research of new clinical end points or methodological approaches for the optimal clinical development of these agents.

Sorafenib

PURPOSE OF REVIEW

Sorafenib is an oral, multikinase inhibitor that was recently approved for use in metastatic renal cancer. It is currently undergoing investigation in locally advanced renal cancer and in other tumor types.

RECENT FINDINGS

Sorafenib was initially developed as an inhibitor of Raf kinase; however, it has broad spectrum activity against multiple tyrosine kinases, including angiogenic factors VEGFR and PDGFR. Common toxicities experienced with sorafenib include hypertension, hand-foot syndrome, rash, diarrhea and fatigue. Early clinical trials suggested that sorafenib acts as a cytostatic agent, as many patients experienced prolonged disease stabilization but insufficient tumor shrinkage to meet RECIST criteria for response. To assess whether sorafenib's growth inhibition translated into a clinical benefit, a phase II randomized discontinuation trial was designed. This trial demonstrated that sorafenib increased progression-free survival in patients with metastatic renal cell cancer; the phase II data were confirmed in a large international phase III trial.

SUMMARY

In this review, we will discuss the clinical development of sorafenib and its role in the treatment of renal cancer. Additionally, we will highlight critical methods of clinical trial design and biomarker development that contribute to the development of sorafenib.

Targeted Therapies in Combination with Chemotherapy in Non–Small Cell Lung Cancer

With rare exceptions, attempts to combine so-called targeted agents with standard cytotoxic chemotherapy in advanced non-small cell lung cancer have yielded disappointing results. The reasons underlying these spectacular failures are not always fully understood, but certainly the lack of careful patient selection is a major contributing factor. In addition, recent preclinical and clinical studies indicate that antagonism may exist between the epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors and chemotherapy primarily in tumor cells with wild-type EGFR. By contrast, tumor cells harboring somatic mutations in EGFR experience massive apoptosis when exposed to the EGFR tyrosine kinase inhibitors. Therefore, in theory, mutant tumor cells should exhibit enhanced cell kill when treated with concomitant chemotherapy and EGFR tyrosine kinase inhibitors akin to what is observed with chemotherapy and trastuzumab in breast cancer. Clinical data from the recently completed TRIBUTE trial support the latter possibility. Ideally, future studies of EGFR tyrosine kinase inhibitors and other targeted drugs will use careful patient selection criteria based on well-characterized and validated predictive markers. However, in the absence of such biomarkers, clinical judgment, common sense, and innovative clinical trial design are necessary to avoid undue delay in drug development.

Improving the design of phase II trials of cytostatic anticancer agents

This paper examines the design of phase II trials in oncology and recommends departing from the traditional uncontrolled trial design. Entrance into phase II clinical evaluation represents a key milestone in the development of any new cancer therapy. As novel molecular-targeted therapies are introduced, whose primary action is to slow the growth of tumors, it will be important to ensure that the clinical trial design will effectively capture any clinical benefit of these agents. The objective of a phase II trial should, in addition to identifying active therapies, be extended to identifying those that are likely to be successful in pivotal trials. It is therefore necessary to quantify the likelihood of either incorrectly halting the development of an active agent or continuing development of an ineffective agent. We believe only randomized studies with comparative intent and including a concurrent active control, can reliably assess these risks corresponding to significance and power. Given that the objective of phase II studies is to identify promising treatments, it is important not be constrained by conventional levels of significance. This paper will review the various approaches to phase II trial design in oncology and provide a framework for fully powered randomized trials of a moderate size. For example, a randomized trial of just 100 patients could lead to the termination of development of 90% of inactive agents whereas at least 80% of agents with a meaningful and realistic increase in progression-free survival would be identified for confirmatory study. We believe randomized studies with progression-free survival endpoints are the most powerful and economical method of determining the clinical activity of new cytostatic agents.

Drug development in oncology: classical cytotoxics and molecularly targeted agents

There is an apparent need to improve the speed and efficiency of oncological drug development. Furthermore, strategies traditionally applied to the development of standard cytotoxic chemotherapy may not be appropriate for molecularly targeted agents. This is particularly the case for exploratory Phase 1 and 2 trials. Conventional approaches to determine dose based on maximum tolerability and efficacy based on objective tumour response may not be suitable for targeted agents, since many of them have a wide therapeutic index and inhibit tumour growth without demonstrable cytotoxicity. Instead, exploratory trials of targeted agents may have to focus on other end-points such as pharmacological effects and disease stabilization. Thus, there is an increasing interest in making the best possible use of biomarkers and pharmacogenomics in early phases of drug development.