The restaging issue.

Patients with persisting involvement of mediastinal lymph nodes after neo-adjuvant therapy have a poor prognosis and do not benefit from surgical resection. Precise restaging after induction treatment is important to determine further treatment and prognosis. Computed tomography (CT) and magnetic resonance imaging (MRI) have a low accuracy in predicting response after induction therapy. Positron emission tomography (PET) has a high sensitivity to detect residual viable disease in the primary tumour but not in the mediastinal lymph nodes. Invasive staging remains necessary to precisely assess mediastinal response. Remediastinoscopy, although technically difficult, has an accuracy of 80% and provides histological proof of mediastinal downstaging. In this way, it is a useful procedure to select patients for thoracotomy after induction therapy. The ultimate overall pathologic response can only be determined by thoracotomy with excision of the primary tumour, hilar and mediastinal lymph nodes.