| For NSCLC and ipsilateral mediastinal lymph node (MLN) involvement, multimodality therapy (MMT) is evaluated in trials (e.g. EORTC 08941) using induction chemotherapy given prior to local therapy to induce downstaging of MLN and eradicate systemic micrometastases. Accurate staging and restaging is important to apply this intensive treatment to the appropriate subset. A retrospective survey had revealed that the diagnostic algorithm used in clinical practice often failed to detect clinically silent disseminated disease (Hoekstra, 2002), and that conventional response evaluation methods were of little prognostic value. FDG PET is a comprehensive technique to stage patients and to monitor response to chemotherapy in an early stage. To evaluate its value in selecting patients for MMT and in predicting the response, a prospective multicenter study was started in 1998, using multiple PET scans prior and during therapy. Clinically unsuspected stage IV was detected by PET in 25% of patients clinically staged as IIIA-N2 (Hoekstra, 2002). The results validated previous response criteria proposed by Vansteenkiste et al for PET applied after completed induction therapy. We further found that residual uptake in the primary tumor after completed, but also already after 1 cycle of chemotherapy, allowed discrimination of long-term survivors and patients with poor outcome. PET improved CT evaluation especially in the group of patients with partial response according to WHO criteria. The performance of quantitative and simplified PET measures was similar (Hoekstra, 2004). |
