The goal of this study is to determine if it is possible to evaluate the efficiency of chemotherapy treatments after one cycle of treatment instead of waiting after 4 cycles, using a new scanner that combines PET and CT modalities. Data available from studies on these combined exams suggest that PET/CT helps to rapidly evaluate the response of the chemotherapy treatment. We also want to verify if some pathological characteristics measured from tumor cells will enable doctors to predict in advance the response to treatment.