Non-inferiority trials in surgical oncology

The classical randomized controlled clinical trial is designed to prove superiority of an investigational therapy over an established therapy or placebo (here referred to as "superiority trial"). Although the randomized controlled superiority trial has its well-grounded role, clinical trials of non-inferiority are equally important in the advance of medical science. Non-inferiority trials test whether a new intervention is as good as a standard treatment with respect to curing the illness (e.g., overall survival) while offering other benefits over the standard therapy, such as lower toxicity, better side-effect profile, improved ease of administration, or reduced costs. The evaluation of non-inferiority is critical in many settings. In surgical oncology, for instance, treatments often combine advantages (e.g., survival benefit) with disadvantages (e.g., high post-operative morbidity due to extensive surgery, considerable toxic effects of an aggressive chemotherapy regimen). The various aspects of different therapeutic strategies may make a treatment decision difficult, requiring a non-inferiority trial to quantify risks and benefits. However, despite their great importance in clinical cancer research, the concept, design, and objectives of non-inferiority trials remain poorly understood in the surgical community. The goal of this review is to discuss the principles, strengths, and challenges of non-inferiority trials and introduce this highly relevant topic to the surgical reader, using examples from the field of surgical oncology.