The Trial within Cohorts (TwiCs) study design in oncology: experience and methodological reflections

A "Trial within a Cohort" platform for pediatric clinical trials on idiopathic nephrotic syndrome: scope, objectives, and design of the retrospective-prospective cohort PIN'SNP

BACKGROUND

Idiopathic nephrotic syndrome (INS) in children is the most common glomerular disease and is characterized by recurrent relapses. There is no community consensus on the treatment of relapsing forms of nephrotic syndrome in children, unlike that for the initial presentation. To date, available treatments only enable relapsing patients to be maintained in remission, rather than modifying the course of the disease; therefore, more therapeutic trials are needed. The Société de Néphrologie Pédiatrique (SNP) decided to implement within its French centers a national coordinated long-term clinical research program for children treated for INS based on a Trials within Cohorts (TwiCs) model. The aim of this paper is to describe the PIN'SNP cohort and research program as well as the TwiCs design adapted to INS research in the French regulatory system.

METHODS

This retrospective-prospective, multicenter research program will rely on a dynamic prospective cohort of children followed for an INS, known as the PIN'SNP cohort (i) to identify cases treated within SNP centers, (ii) to describe their clinical and epidemiological characteristics, and (iii) to provide a platform to nest prospective trials, and thus facilitate inclusion of patients in these future trials.

CONCLUSIONS

The PIN'SNP cohort is the first French national pediatric platform dedicated to the implementation of randomized nested trials along with longitudinal and observational studies on INS in children. The adaptation of the TwiCs design to inform all eligible patients/parents to each nested trial will facilitate methodological robustness and ethical acceptability and reinforce communication between investigators and participants.

TRIAL REGISTRATION

number NCT04207580.

PrimerX: A Bayesian Multistage Cohort Embedded Randomised Trial to Evaluate the Role of Deferred Local Therapy of the Primary Tumour in Combination with Immune Checkpoint Inhibitor-based First-line Therapy in Metastatic Renal Cell Carcinoma Patients

Background

Historically, patients with metastatic renal cell carcinoma (mRCC) have been offered upfront cytoreductive nephrectomy (CN) followed by systemic therapy. Currently, CN is no longer the standard of care (SOC) based on the randomised phase 3 CARMENA study performed in the vascular endothelial growth factor receptor tyrosine kinase inhibitor era. With the advent of immune checkpoint inhibitor (ICI) combination therapy in first line, the role of CN needs to be reassessed. There is indirect evidence from small retrospective series that deferred CN after ICI combination therapy may lead to better outcomes. To reassess the role of CN, we designed PrimerX, a randomised controlled trial following the Trial within Cohorts (TwiCs) study design. The primary objective of this study is to re-evaluate the benefit of deferred local treatment in the current era of immunotherapy.

Study design

This PrimerX study has been designed as a TwiCs study within the Dutch Prospective Renal Cell Carcinoma (PRO-RCC) cohort. The PRO-RCC cohort includes patients with mRCC and nonmetastatic RCC, and has been set up for prospective collection of long-term clinical data and as an infrastructure for initiating TwiCs studies. The PrimerX TwiCs trial follows a Bayesian adaptive multistage design to allow for early discontinuation due to futility or efficacy. PrimerX has appropriate ethics approval and is registered at clinical.trials.gov (NCT05941169).

End points

The primary clinical endpoint is overall survival, defined as the time from randomisation to death from any cause. The secondary endpoint is the objective response rate within the primary tumour prior to local therapy, as assessed by a computed tomography scan.

Patients and methods

A maximum of 700 patients with synchronous mRCC and absence of progression at metastatic sites following at least 6 mo of standard first-line ICI combination therapy will be assigned randomly to receive local treatment of the primary tumour (experimental arm) or SOC (control arm). The experimental intervention consists of (partial) CN, any form of ablative local therapy, or magnetic resonance imaging guided ablative stereotactic radiotherapy, performed within 6 mo and 1.5 yr after the start of systemic treatment.

Tailored guidance to apply the Estimand framework to Trials within Cohorts (TwiCs) studies

Objective: The estimand framework offers a structured approach to define the treatment effect to be estimated in a clinical study. Defining the estimand upfront helps formulating the research question and informs study design, data collection and statistical analysis methods. Since the Trials within Cohorts (TwiCs) design has unique characteristics, the objective of this study is to describe considerations and provide guidance for formulating estimands for TwiCs studies. Methods: The key attributes of an estimand are the target population, treatments that are compared, the endpoint, intercurrent events and their handling, and the population-level summary measure. The estimand framework was applied retrospectively to two TwiCs studies: the SPONGE and UMBRELLA Fit trial. The aim is to demonstrate how the estimand framework can be implemented in TwiCs studies, thereby focusing on considerations relevant for defining the estimand. Three estimands were defined for both studies. For the SPONGE trial, estimators were derived. Results: Intercurrent events considered to occur exclusively or more frequently in TwiCs studies compared to conventional randomized trials included intervention refusal after randomization, misalignment of timing of routine cohort measurements and the intervention period, and participants in the control arm initiating treatments similar to the studied intervention. Considerations for handling refusal after randomization related to decisions on whether the target population should include all eligible participants or the subpopulation that would accept (or undergo) the intervention when offered. Considerations for handling treatment initiation in the control arm and misalignments of timing related to decisions on whether such events should be considered part of treatment policy or whether interest is in a hypothetical scenario where such events do not occur. Conclusion: The TwiCs study design has unique features that pose specific considerations when formulating an estimand. The examples in this study can provide guidance in the definition of estimands in future TwiCs studies.

Towards a European prospective data registry for particle therapy

The evidence for the value of particle therapy (PT) is still sparse. While randomized trials remain a cornerstone for robust comparisons with photon-based radiotherapy, data registries collecting real-world data can play a crucial role in building evidence for new developments. This Perspective describes how the European Particle Therapy Network (EPTN) is actively working on establishing a prospective data registry encompassing all patients undergoing PT in European centers. Several obstacles and hurdles are discussed, for instance harmonization of nomenclature and structure of technical and dosimetric data and data protection issues. A preferred approach is the adoption of a federated data registry model with transparent and agile governance to meet European requirements for data protection, transfer, and processing. Funding of the registry, especially for operation after the initial setup process, remains a major challenge.

The effect of physical exercise during radiotherapy on physical performance in patients with head and neck cancer: a trial within cohorts study protocol, the vital study

BACKGROUND

During the last decade, twelve studies have been published investigating physical exercise interventions (PEIs) in patients with head and neck cancer (HNC) during radiotherapy (RT), chemoradiation (CRT) or bioradiation (BRT). These studies showed that these PEIs are safe and feasible. However, only two of these studies were randomised clinical trials (RCTs) with a satisfying sample size. Thereby, there is no cost-effectiveness study related to a PEI during RT, CRT or BRT ((C/B)RT) for patients with HNC. Therefore, the aim of this study is to investigate and compare physical performance, muscle strength, fatigue, quality of life (QoL), body mass index (BMI), nutritional status, physical activity, treatment tolerability, and health care related costs in patients with HNC with and without a 10 week PEI during (C/B)RT.

METHODS

This study, based on a trial within cohorts (TwiCs) design, will contain a prospective cohort of at least 112 patients. Fifty-six patients will randomly be invited for an experimental 10 week PEI. This PEI consists of both resistance and endurance exercises to optimize physical performance, muscle strength, fatigue, QoL, BMI, nutritional status, physical activity, and treatment tolerability of (C/B)RT. Measurements are at baseline, after 12 weeks, 6 months, and at 12 months. Statistical analyses will be performed for intention-to-treat and instrumental variable analysis.

DISCUSSION

This study seeks to investigate physical, QoL, and economic implications of a PEI. With a substantial sample size, this study attempts to strengthen and expand knowledge in HNC care upon PEI during (C/B)RT. In conclusion, this study is dedicated to provide additional evidence for PEI in patients with HNC during (C/B)RT.

TRIAL REGISTRATION

protocol was registered at clinicaltrials.gov with number NCT05988060 on 3 August 2023.