LUNG-CANCER STAGING - THE ROLE OF COMPUTED-TOMOGRAPHY AND MAGNETIC-RESONANCE-IMAGING

Because complete resection remains the only reliable method of cure of lung cancer, one important aim of preoperative staging is to select p atients with localised disease who may benefit from surgery, while avo iding unnecessary thoracotomies in patients with unresectable neoplasm . Computed tomography (CT) of the chest is a valuable method for stagi ng local and regional spread of lung neoplasms, although limitations i n its accuracy are well-known. While gross invasion of the mediastinum and major structures as well as the presence of metastatic disease ca n be easily demonstrated with CT, differentiation between tumour conti guity and subtle invasion of mediastinum or chest wall often remains a problem. Although magnetic resonance imagaing (MRI) may have the same limitations as CT, in specific situations it may b superior in diagno sing minimal chest wall or mediastinal invasion. Moreover, MRI is usef ul in the assessment of patients with superior sulcus tumours as well as in patients with contraindication to intravenous administration of ionic contrast material. Since nodal size is the only useful criterion for evaluating lymph node metastases, CT and MRI show similar, poor a ccuracies in lymph node staging reesulting from both low sensitivity ( normal-sized nodes may contain microscopic metastases) and low specifi city (enlarged lymph nodes may be reactive). For this reason, if enlar ged lymph nodes are detected, further evaluation is recommended before excluding the patient from a potentially curative resection. Advantag es and limitations of CT and MRI in the preoperative staging of non-sm all-cell carcinoma are reviewed in this article. The imaging of small- cell carcinoma is not included because most patients with this cell ty pe do not benefit from surgical resection. Similarly we do not discuss imaging of distant metastases.