Structural changes induced by antineoplastic therapies: keys to evaluate tumor response to treatment

The criteria to define therapeutic response in oncology are those proposed by Miller, characterized by four response categories (complete response, partial response, no change, progression of disease), and based upon both measurable and non-measurable (and otherwise assessable) morphological parameters in comparison with baseline and subsequently modified following the Response Evaluation Criteria In Solid Tumors. In addition to these classical morphological criteria, we review the predictive value of structural changes in the evaluation of response to antineoplastic therapies. The goal of the present review is to evaluate in detail structural variations (calcification, fibrosis, differentiation, necrosis, cavitation, vascularization, edema, and pseudocapsule formation) induced by therapy, and to ascertain their significance in terms of biological evolution of the neoplastic process.