Imaging surrogates of tumor response to therapy: Anatomic and functional biomarkers

This article addresses the current status of quantitative imaging as a surrogate biomarker for the assessment of tumor response to therapy with non–small cell lung cancer as an example. In addition, the article discusses the limitations of conventional re-sponse criteria in the new era of molecular-targeted agents for cancer treatment; the increasing need for more accurate and early response-assessment methods, particularly for volumetric CT; new tumor-specific radiotracers and molecular imaging technologies; and the future applications of molecular imaging with PET for studying various features of cancer metabolism, endocrine status, hypoxia, and oncofetal and differentiation antigens. Key Words: response assessment; surrogate biomarker; functional/molecular imaging; volumetric CT; lung cance