Purpose of review: To describe the difficulty in assessing the biological activity of a novel agent in phase II trials.
Recent findings: Two major fields of research provide interesting new potential endpoints: endpoints based on new imaging techniques (e.g. PET or spectral imaging that explore tumour metabolism, dynamic contrast enhanced (DCE) ultrasonography or DCE-MRI that explore tumour vascularization and tumour growth inhibition) and endpoints integrating assessment of tumour burden across time, such as the growth modulation index.
Summary: Most of the recently described techniques appear attractive, but require formal validation.