Early-Phase Platform Trials: A New Paradigm for Dose Finding and Treatment Screening in the Era of Precision Oncology

Adaptive magnetic resonance image guided radiation for intact localized prostate cancer how to optimally test a rapidly emerging technology

Introduction

Prostate cancer is a common malignancy for which radiation therapy (RT) provides an excellent management option with high rates of control and low toxicity. Historically RT has been given with CT based image guidance. Recently, magnetic resonance (MR) imaging capabilities have been successfully integrated with RT delivery platforms, presenting an appealing, yet complex, expensive, and time-consuming method of adapting and guiding RT. The precise benefits of MR guidance for localized prostate cancer are unclear. We sought to summarize optimal strategies to test the benefits of MR guidance specifically in localized prostate cancer.

Methods

A group of radiation oncologists, physicists, and statisticians were identified to collectively address this topic. Participants had a history of treating prostate cancer patients with the two commercially available MRI-guided RT devices. Participants also had a clinical focus on randomized trials in localized prostate cancer. The goal was to review both ongoing trials and present a conceptual focus on MRI-guided RT specifically in the definitive treatment of prostate cancer, along with developing and proposing novel trials for future consideration. Trial hypotheses, endpoints, and areas for improvement in localized prostate cancer that specifically leverage MR guided technology are presented.

Results

Multiple prospective trials were found that explored the potential of adaptive MRI-guided radiotherapy in the definitive treatment of prostate cancer. Different primary areas of improvement that MR guidance may offer in prostate cancer were summarized. Eight clinical trial design strategies are presented that summarize options for clinical trials testing the potential benefits of MRI-guided RT.

Conclusions

The number and scope of trials evaluating MRI-guided RT for localized prostate cancer is limited. Yet multiple promising opportunities to test this technology and potentially improve outcomes for men with prostate cancer undergoing definitive RT exist. Attention, in the form of multi-institutional randomized trials, is needed.

Guidelines for clinical evaluation of anti-cancer drugs

Clinical studies intended for regulatory approval must demonstrate the clinical benefits of the drug in a target population. Clinical development of a drug proceeds by stepwise clinical studies; after safety and pharmacokinetics are evaluated and the recommended dosage and administration are determined, efficacy and safety are evaluated in an exploratory manner, and finally clinical benefits are compared with conventional standard therapies. Guidelines for the clinical evaluation of anti‐cancer drugs in Japan were established in 1991 and amended in 2006 after molecular‐targeted drugs were introduced. Recent progress in the development of drugs acting on the immune system and cancer genomic medicine targeting rare but important molecular subtypes have altered the strategy for development of anti‐cancer drugs. It is often difficult to conduct a confirmatory randomized controlled study using overall survival as the primary endpoint in rare molecular subtypes, and the primary evaluation of the efficacy of some drugs and subsequent approval is based on the tumor response. As conducting clinical studies for rare subtypes solely within Japan is difficult, drug development needs to be conducted within a global study. However, this requires robust monitoring to detect possible ethnic differences in pharmacokinetics and drug efficacy. Development using the conditional approval system for drugs enforced in 2020 may be considered, when clinical utility is evaluated based on surrogate endpoints. Because of these changes, we have revised the guidelines for the clinical evaluation of anti‐cancer drugs in Japan. To promote global development of anti‐cancer drugs involving Japan, the guidelines have been translated into English.

Recent progress in development of drugs acting on the immune system and cancer genomic medicine targeting rare but important molecular subtypes have altered the strategy for development of anti‐cancer drugs. As conducting clinical studies for rare subtypes solely within Japan is difficult, drug development needs to be conducted within a global study with monitoring possible ethnic differences. Because of these changes, we have revised the guidelines for the clinical evaluation of anti‐cancer drugs in Japan.