Tumor Response to Treatment: Prediction and Assessment

Neoadjuvant therapy has become part of standard treatment in several types of cancer. Therapeutic effects are often assessed with imaging. The main purpose of response assessment is to define resectability and determine surgical approach. Another controversial purpose of response assessment is selecting patients with complete tumor regression for non-operative strategies. Moreover, response prediction early during treatment can lead to alteration of the initial treatment plan. Another role for pre-treatment imaging lies in the assessment of individual tumor risk profile, to select which patients benefit most from neoadjuvant therapy. Finally, there is a new role for imaging in the guidance of treatment efficacy. This review discusses the different imaging modalities used in clinics to evaluate and predict treatment response in various tumor types. Established response methods such as recist and fdg-pet are discussed. Functional imaging methods such as diffusion-weighted mr imaging, perfusion imaging, and novel pet-imaging techniques are described.