Significance of a new fluorodeoxyglucose-positive lesion on restaging positron emission tomography/computed tomography after induction therapy for non-small-cell lung cancer.

Objectives: Restaging of patients with locally advanced non-small-cell lung cancer (NSCLC) is of paramount importance, since only patients with down-staging after induction therapy will benefit from surgery. In this study, we assessed the aetiology of new (18)fluoro-2-deoxy-d-glucose (FDG)-positive focal abnormalities on restaging positron emission tomography/computed tomography (PET/CT) in patients with a good response after induction chemotherapy in the primary tumour and lymph nodes.

Methods: Between 2004 and 2008, 31 patients with histological proven stage III NSCLC had a PET/CT prior and after induction chemotherapy. Their medical charts were retrospectively reviewed.

Results: Restaging PET/CT revealed a new FDG-positive lesion in 6 of 31 (20%) patients. The initial clinical stage of the disease was IIIA N2 in four and IIIB T4 in two patients. The maximal standard uptake value in the primary tumour (P = 0.043) and in the initially involved mediastinal nodes (P = 0.068) decreased after induction treatment in all patients. The new PET/CT findings were located in an ipsilateral cervical lymph node in two patients, a contralateral mediastinal in one patient and an ipsilateral mammary internal lymph node in one patient. Two other patients had a lesion on the contralateral lung. Malignant lymph node infiltrations were excluded following fine-needle puncture, intraoperative biopsy or follow-up PET/CT. Contralateral pulmonary lesions were diagnosed as benign following mini thoracotomy and pulmonary wedge resection.

Conclusions: New solitary FDG-positive lesions on restaging PET/CT after induction chemotherapy for NSCLC are not rare in good responders to chemotherapy. In our experience, all these lesions were not associated with malignancy.