Cancer is a family of similar but different diseases. They overlap to some extent in their physiological origins, anatomical sites, diagnostic criteria and prognoses, but still differ sufficiently to warrant separate treatment strategies and imaging options. Which biochemical markers, imaging markers and image acquisition techniques are most applicable in oncology clinical trials depends on whether the focus is on the primary tumor response, local recurrence or distant metastases.  Biomarkers in oncology can be either imaging markers of tumor morphology; tumor microvascularity, tumor integrity or tumor metabolism; or biochemical markers related to tissue destruction and products of the tumor itself.

Response evaluation will differ depending on the type of therapy used. Background changes due to local radiation and chemotherapy must be differentiated from those related to the neoplasm itself, and traditional tumor response criteria are inappropriate for monitoring angiostatic and cytostatic agents which retard tumor growth and metastatic spread, rather than shrink the lesions.

This example outlines the fundamental differences between these biomarkers and illustrates their utility in clinical trials.