Quantitative imaging for evaluation of response to cancer therapy.

Advances in molecular medicine offer the potential to move cancer therapy beyond traditional cytotoxic treatments to safer and more effective targeted therapies based on molecular characteristics of a patient's tumor. Within this context, the role of quantitative imaging as an in vivo biomarker has received considerable attention as a means to predict and measure the response to therapy. For example, the ability to predict the response to therapy quantitatively, early in the drug or radiation therapy regime, would facilitate adaptive therapy trial strategies, that is, that permit alternative treatment regimens in cases where initial therapy response was ineffective. Similarly, the ability to measure the response to therapy should provide a more robust means for both therapy dose management and correlation of imaging results with other laboratory biomarkers. The latter is required for clinical decision making in the clinical setting. The National Cancer Institute (NCI) in collaboration with the Food and Drug Administration (FDA) has therefore promoted a number of initiatives supporting the role of molecular imaging in drug trials. The major goal of these initiatives is the “qualification” of the proposed molecular imaging protocol(s) that can be incorporated into current or future drug trials submitted to the FDA. Clinical research strategies that will help achieve these goals are described in the published literature [1–5].