Imaging Biomarker Applications in Oncology Drug Development

At present, drug development is a long and costly process with an unacceptably high failure rate. As a result, both the Food and Drug Administration and the pharmaceutical industry have shown interest in using biomarkers of clinical response. Biomarker imaging is noninvasive, allows serial data collection, and lessens interpatient variability because each individual can serve as his or her own control. The only imaging biomarker currently accepted as a surrogate for clinical response is tumor shrinkage for accelerated approval. The imaging biomarker,18F-fluoro-2-deoxy-D-glucose (FDG) and positron emission tomography (PET), is widely used clinically to assess response to therapy and, in some cases, correlates better with prolonged survival than tumor shrinkage. Other biomarkers, such as hemodynamic biomarkers, have been used in early clinical trials as a means to assess bioactivity within hours or days of the start of treatment and to determine drug dose in subsequent trials. Many others have found applications in assessing bioactivity in preclinical stages of drug development. With further validation, many of these imaging biomarkers could become valuable in measuring response to therapy much faster than present methods. In addition, pharmacokinetic imaging will provide both clinical and preclinical data on uptake, distribution, and excretion of drug candidates.