Two-stage Trial Design Research Articles

Optimising the two-stage randomised trial design when some participants are indifferent in their treatment preferences.

Outcomes in a clinical trial can be affected by any underlying preferences that its participants have for the treatments under comparison and by whether they actually receive their preferred treatment. These effects cannot be evaluated in standard trial designs but are estimable in the alternative two-stage randomised trial design, in which some patients can choose their treatment, while the rest are randomly assigned. We have previously shown that, when all two-stage trial participants have a preferred treatment, the preference effects can be evaluated, in addition to the usual direct effect of treatment. We also determined criteria by which to optimise how many participants should be given a choice of treatment vs being randomised. More recently, we extended our methodology to allow for participants who are unable or unwilling to express a treatment preference if they are assigned to the choice group. In this paper, we show how to optimise the two-stage design when some participants are undecided about their treatment. We demonstrate that the undecided group should be regarded as distinct in the analysis, to obtain valid estimates of the preference effects. We derive the optimal proportion of participants who should be offered a choice of treatment, which in many cases will be close to 50%. More generally, the optima depend on the preference rates for treatments and the proportion of undecided participants, and the parameters of primary interest. We discuss some advantages and disadvantages of the two-stage trial design in this situation and describe a practical example.

Optimized adaptive enrichment designs.

Based on a Bayesian decision theoretic approach, we optimize frequentist single- and adaptive two-stage trial designs for the development of targeted therapies, where in addition to an overall population, a pre-defined subgroup is investigated. In such settings, the losses and gains of decisions can be quantified by utility functions that account for the preferences of different stakeholders. In particular, we optimize expected utilities from the perspectives both of a commercial sponsor, maximizing the net present value, and also of the society, maximizing cost-adjusted expected health benefits of a new treatment for a specific population. We consider single-stage and adaptive two-stage designs with partial enrichment, where the proportion of patients recruited from the subgroup is a design parameter. For the adaptive designs, we use a dynamic programming approach to derive optimal adaptation rules. The proposed designs are compared to trials which are non-enriched (i.e. the proportion of patients in the subgroup corresponds to the prevalence in the underlying population). We show that partial enrichment designs can substantially improve the expected utilities. Furthermore, adaptive partial enrichment designs are more robust than single-stage designs and retain high expected utilities even if the expected utilities are evaluated under a different prior than the one used in the optimization. In addition, we find that trials optimized for the sponsor utility function have smaller sample sizes compared to trials optimized under the societal view and may include the overall population (with patients from the complement of the subgroup) even if there is substantial evidence that the therapy is only effective in the subgroup.

206P - Bevacizumab plus dose-dense neoadjuvant FEC followed by docetaxel chemotherapy in patients with HER2-negative breast cancer: a multicentre, phase 2 study by the Hellenic Oncology Research Group

Addition of bevacizumab to standard chemotherapy in the neoadjuvant setting improves the proportion of patients with HER2-negative breast cancer who achieve pathological complete response. We aimed to assess the addition of bevacizumab to dose-dense neoadjuvant chemotherapy. We enrolled women with operable HER2-negative breast cancer (T1c-T4 and N0-3). Patients underwent treatment every 2 weeks (with pegfilgrastim support) of fluorouracil (500 mg/m2), epirubicin (75 mg/m2), cyclophosphamide (500 mg/m2), and bevacizumab (10 mg/kg) for 4 cycles followed by docetaxel (75 mg/m2) and bevacizumab for 4 cycles. After surgery, patients received adjuvant radiotherapy, and hormone therapy (if indicated). The primary endpoint was pathological complete response in breast and the axilla, and safety of the combination. A two-stage trial design was planned with 15 and 33 patients to enroll, respectively. The trial was terminated early due to slow accrual and follow-up is ongoing. Between Oct, 2011, and Apr, 2015, we enrolled 34 patients, of whom 3 didn't undergo surgery, leaving 31 patients in the primary endpoint analysis. After neoadjuvant therapy, 5 (16.1%) of 31 patients achieved a pathological complete response according to centralized review. No patient discontinued treatment due to adverse events. The most frequent grade 3–4 toxicities were neutropenia (23.5%), nausea and vomiting (5,8%), and febrile neutropenia (2,9%). Only one patient developed grade III bevacizumab-related toxicity (hypertention). One patient died of pneumonia after cycle 8 and before surgery, which was thought to be unrelated to bevacizumab. After 25,2 months of median follow-up (range: 2,3-43,3) five patients experienced a disease relapse (16,1%). Our results seem to indicate that the addition of bevacizumab to dose-dense neoadjuvant chemotherapy with FEC and docetaxel, although safe and feasible, does not provide clinical benefit to patients with non-metastatic HER2-negative breast cancer. Translational research to identify patients who might benefit from bevacizumab is needed.

Prospective study evaluating the relative sensitivity of 18F-NaF PET/CT for detecting skeletal metastases from renal cell carcinoma in comparison to multidetector CT and 99mTc-MDP bone scintigraphy, using an adaptive trial design

BackgroundThe detection of occult bone metastases is a key factor in determining the management of patients with renal cell carcinoma (RCC), especially when curative surgery is considered. This prospective study assessed the sensitivity of 18F-labelled sodium fluoride in conjunction with positron emission tomography/computed tomography (18F-NaF PET/CT) for detecting RCC bone metastases, compared with conventional imaging by bone scintigraphy or CT. Patients and methodsAn adaptive two-stage trial design was utilized, which was stopped after the first stage due to statistical efficacy. Ten patients with stage IV RCC and bone metastases were imaged with 18F-NaF PET/CT and 99mTc-labelled methylene diphosphonate (99mTc-MDP) bone scintigraphy including pelvic single photon emission computed tomography (SPECT). Images were reported independently by experienced radiologists and nuclear medicine physicians using a 5-point scoring system. ResultsSeventy-seven lesions were diagnosed as malignant: 100% were identified by 18F-NaF PET/CT, 46% by CT and 29% by bone scintigraphy/SPECT. Standard-of-care imaging with CT and bone scintigraphy identified 65% of the metastases reported by 18F-NaF PET/CT. On an individual patient basis, 18F-NaF PET/CT detected more RCC metastases than 99mTc-MDP bone scintigraphy/SPECT or CT alone (P = 0.007). The metabolic volumes, mean and maximum standardized uptake values (SUVmean and SUVmax) of the malignant lesions were significantly greater than those of the benign lesions (P < 0.001). Conclusions18F-NaF PET/CT is significantly more sensitive at detecting RCC skeletal metastases than conventional bone scintigraphy or CT. The detection of occult bone metastases could greatly alter patient management, particularly in the context when standard-of-care imaging is negative for skeletal metastases.

Identifying combined design and analysis procedures in two‐stage trials with a binary end point

Two-stage trial designs provide the flexibility to stop early for efficacy or futility and are popular because they have a smaller sample size on average than a traditional trial has with the same type I and II error rates. This makes them financially attractive but also has the ethical benefit of reducing, in the long run, the number of patients who are given ineffective treatments. Designs that minimise the expected sample size are often referred to as ‘optimal’. However, two-stage designs can impart a substantial bias into the parameter estimate at the end of the trial. In this paper, we argue that the expected performance of one's chosen estimation method should also be considered when deciding on a two-stage trial design. We review the properties of standard and bias-adjusted maximum likelihood estimators as well as mean and median unbiased estimators. We then identify optimal two-stage design and analysis procedures that balance projected sample size considerations with those of estimator performance. We make available software to implement this new methodology. Copyright © 2012 John Wiley & Sons, Ltd.

New clinical trial of DNA-based vaccines for patients with non-small cell lung cancer.

e13034 Background: We report a new immunotherapeutic trial for patients with non-small cell lung cancer (NSCLC). The trial to be conducted at the University of Pittsburgh Cancer Institute is a two-stage uncontrolled non-randomized Phase IB study designed to evaluate the safety, immunogenicity and feasibility of a new vaccine, consisting of human allogeneic fibroblasts transfected with DNA derived from the patient’s own tumor. The vaccine is prepared by transfer of genomic DNA-fragments (25 kb) from the patient’s tumor into MRC-5 cells, a human embryonic fibroblast cell line. The rationale is that numerous mutant and dysregulated genes in the tumor specifying an array of patient-specific tumor antigens are expressed in a highly immunogenic form by the DNA-transfected cells. A large body of preclinical studies in tumor-bearing mice supports this approach. An IND has been issued. Cohort 1 is underway without DLT. Methods: We plan to use a two-stage trial design. Initially, 15 early-stage patients with NSCLC will be enrolled. If there is no evidence of toxicity, and &gt;3 of the initial patients show an immunologic response, the second stage of the study will be opened for the accrual of 22 additional patients. A portion of the primary tumor removed at surgery will be obtained to serve as a source of tumor-DNA. Each vaccine will contain 1 X 10E7 DNA-transfected fibroblasts. The vaccine will be lethally irradiated before it is administered. It will be injected intradermally in the Outpatient Clinic. Immunologic responses to the vaccine and to the autologous tumor will be evaluated by IFN-g secretion in ELISPOT assays prior to and after vaccination for the frequency of T-cells responsive to the autologous tumor. Additional assays will include lymphocyte proliferation determinations in response anti CD3 and anti CD28 monoclonal antibodies and the effect of the immunizations on the proportion of myeloid-derived suppressor T cells in the patient’s peripheral blood. The patients will also be evaluated before and after immunization for the capacity of their T cells to respond to activating signals delivered via the T cell receptor (TcR). Results: Vaccines have been prepared. First patient has been enrolled. Conclusions: No data to report in this early trial.

Designs for clinical trials with time-to-event outcomes based on stopping guidelines for lack of benefit

backgroundThe pace of novel medical treatments and approaches to therapy has accelerated in recent years. Unfortunately, many potential therapeutic advances do not fulfil their promise when subjected to randomized controlled trials. It is therefore highly desirable to speed up the process of evaluating new treatment options, particularly in phase II and phase III trials. To help realize such an aim, in 2003, Royston and colleagues proposed a class of multi-arm, two-stage trial designs intended to eliminate poorly performing contenders at a first stage (point in time). Only treatments showing a predefined degree of advantage against a control treatment were allowed through to a second stage. Arms that survived the first-stage comparison on an intermediate outcome measure entered a second stage of patient accrual, culminating in comparisons against control on the definitive outcome measure. The intermediate outcome is typically on the causal pathway to the definitive outcome (i.e. the features that cause an intermediate event also tend to cause a definitive event), an example in cancer being progression-free and overall survival. Although the 2003 paper alluded to multi-arm trials, most of the essential design features concerned only two-arm trials. Here, we extend the two-arm designs to allow an arbitrary number of stages, thereby increasing flexibility by building in several 'looks' at the accumulating data. Such trials can terminate at any of the intermediate stages or the final stage.MethodsWe describe the trial design and the mathematics required to obtain the timing of the 'looks' and the overall significance level and power of the design. We support our results by extensive simulation studies. As an example, we discuss the design of the STAMPEDE trial in prostate cancer.ResultsThe mathematical results on significance level and power are confirmed by the computer simulations. Our approach compares favourably with methodology based on beta spending functions and on monitoring only a primary outcome measure for lack of benefit of the new treatment.ConclusionsThe new designs are practical and are supported by theory. They hold considerable promise for speeding up the evaluation of new treatments in phase II and III trials.