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Objective: Accurate pre-operative staging is essential for the optimal management of patients with lung cancer. An important goal of pre-operative staging is to identify mediastinal lymph node metastases. Computed tomography (CT) and positron emission tomography (PET) may identify mediastinal lymph node metastases with sufficient sensitivity to allow omission of mediastinoscopy. This study utilizes our experience with clinical stage I lung cancer patients to perform a decision analysis addressing whether mediastinoscopy should be performed in clinical stage I lung cancer patients staged by CT and PET scans.
Methods: We retrospectively reviewed our thoracic surgery database between May 1999 and May 2004. Patients deemed clinical stage I by CT and PET were chosen for further study. Individual CT, PET, operative and pathology reports were reviewed. The post-resection pathologic staging and long-term survival were recorded. A decision model was created using TreeAgePro software and our observed data for the prevalence of mediastinal lymph node metastases. Data reported in the literature was also utilized to complete the decision analysis model. A sensitivity analysis of key variables was performed.
Results: A total of 195 patients with clinical stage I lung cancer were identified. One hundred forty-nine patients (76%) underwent mediastinoscopy before resection, and 4/149 (2.7%) showed N2 disease. An additional 7 patients were found to have N2 disease in the final resected specimen, resulting in a total of 11/195 patients (5.6%) with occult mediastinal lymph node metastases. Decision analysis determined that the no-mediastinoscopy policy dominated: it was both cheaper and more effective than routine mediastinoscopy. The outcome was sensitive to the prevalence of N2 disease in the population. When the prevalence of N2 disease exceeds 10%, the sensitivity analysis predicts that mediastinoscopy would lengthen life, but only at a cost per quality adjusted life year gained of more than $400,000.
Conclusions: Patients with clinical stage I lung cancer staged by CT and PET do not appear to benefit from mediastinoscopy. The prevalence of N2 disease would have to be more than double the observed rates to make mediastinoscopy more effective than the no mediastinoscopy strategy.

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