Molecular imaging in cancer therapy

Targeted drugs that modulate the function of specific molecules in diseased tissues hold great promise for the treatment of many diseases, including malignant tumors. However, there are several challenges for the efficient evaluation of these drugs in clinical trials as well as for the use in clinical practice. These include (i) the selection of patients likely to benefit from treatment with a specific targeted drug, (ii) finding the right dose and dose schedule, (iii) monitoring target inhibition, and (iv) assessing tumor response to therapy. Standard anatomic imaging continues to play an important role for addressing these challenges, but molecular imaging provides several new opportunities to make the use of targeted drugs more efficient. Using molecular imaging, the expression of drug targets can be assessed noninvasively, the concentration of drugs can be measured in the tumor tissue, target inhibition can be monitored, and tumor response to therapy can be evaluated earlier than with anatomic imaging techniques. Therefore, it is expected that molecular imaging will play an increasing role for guiding molecularly defined therapeutic interventions.