Evaluation of response: new and standard criteria.

Most cancer patients suffering from some form of advanced or locally advanced cancer will be treated with anticancer agents to stop the natural evolution of the disease. Anticancer agents developed over the last four decades behave as cytotoxic drugs inducing tumor regression, sometimes also resulting in prolongation of survival. Historically, the direct therapeutic efficacy of such treatments has been monitored through successive evaluations of the size of tumor lesions that were clinically or radiologically evaluable. This process of evaluation of response to treatment is nowadays integrated into the daily practice of every oncologist and is also used in the investigational setting (clinical trials) to define the antitumor activity of new anticancer agents (or combination of agents). Sometimes, the level of anticancer activity may be associated with other indicators (duration of response, type of response, time to progression, etc.) to document the therapeutic efficacy (clinical benefit) procured to the patients.