Moving the goalposts while scoring―the dilemma posed by new PET technologies

In this review, we provide a comprehensive description of the principles behind recent technological innovations, elucidate the current evidence, and point to specific fields of clinical care in which adoption of the most advanced technology, without careful thought, may put the previously established clinical role and benefits of PET at risk.In doing so, the authors will not argue that the introduction of new PET technology is in any way undesirable, but rather that during this process more emphasis should be placed on its ultimate effect on patient-relevant outcomes-on the possible limitations as well as the desired advantages.This review belongs to a two-part series of reviews published in EJNMMI addressing the pros and cons of new PET technologies.The complementary review by Nicolas Aide et al. covers the pros [1]. How should we evaluate the clinical benefits of PET and PET technologies?The fundamental role of PET in clinical oncology is firmly established.This recognition of its clinical value has been achieved stepwise over time, by providing patients and clinicians with crucial additional information concerning tumor characterization, biology, and metastatic spread.However, this has been paralleled by concerns that in the average patient, PET may lead to overdiagnosis and overtreatment as a more sensitive imaging method.Before PET was introduced and before the concept of evidence-based medicine was widely adopted in the 1990s [2], there was generally no demand for a systematic and standardized assessment of the clinical benefit of any one imaging procedure.However, in evaluating the importance of PET imaging and PET technology today, medical societies and regulatory authorities ask for proof of actual clinical benefit to the individual patient-just as they do for development and approval of therapeutic drugs.Fryback and Thornbury have proposed six hierarchical levels of evidence for the clinical efficacy of diagnostic imaging (Fig. 1) [3].In accordance with this system, for regulatory purposes, evidence of improved patient outcomes usually implies level 5 evidence.This requires proof of an advantage with regard to patient morbidity (e.g., as a consequence of a reduced rate of invasive procedures or futile surgeries), mortality, or quality of life [4].In specific cases, proof of superior This article is part of the Topical Collection on Technology