Abstract #832: Resistance is an inappropriate concept for biological drug such as trastuzumab

Development of novel therapies specifically targeting key molecular events responsible of malignant phenotype arise the problem to update selection criteria of patient population most likely to benefits and to define the readout of the clinical benefits. To date, the first issue can be apply to few molecules, i.e. ER and HER2, since selection of patients highly expressing targets define the population will benefits of the treatments. For most molecular targeted drugs, dependency of targeted expression is not sufficient to define population that can achieved responses. The second issue considered that these novel therapies have no primarily cytotoxic action and, therefore, they are not expected to results in tumor shrinkage, invalidating the response criteria used till now to define clinical benefits to chemotherapy. Therefore, we need to define the therapy end-points oncologist should used to interpret patients\#8217; response to new therapy and verify weather the concept of resistance can be apply to these molecular drugs. To address this aim we analyzed 440 consecutive HER2-positive metastatic breast carcinoma patients treated with trastuzumab from 2000/2001 in 22 Italian oncologic centers. According to Recist criteria, responses (complete plus partial) to trastuzumab-based treatment were achieved in 189/440 (43%), with 102/189 (54%) complete responders. Patients who responded to treatment survived significantly longer than did non-responders (chi-square of log-rank test = 20.62, p Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 832.