PET-CT compared to invasive mediastinal staging in non-small cell lung cancer (NSCLC)

7575 Background: In patients with NSCLC, preoperative staging tests including mediastinoscopy (M) are important in defining which patients are surgical candidates. 18 FDG PET-CT is useful in identifying patients with mediastinal disease not evident by CT. Alternatively, M may not be required if PET-CT is negative. We have previously reported reduced rates of unnecessary thoracotomy (T) in the PET-CT arm of a trial which compared staging with PET-CT versus conventional imaging (bone scan and CT liver and adrenals) in patients with clinical stage I, II, or IIIA NSCLC being considered for surgery (J Clin Oncol 26 May 20 suppl: abstr 7502). Methods: In this analysis, we determined the accuracy of PET-CT in mediastinal staging compared to invasive surgical staging either by M alone or by M and T. Patients in the PET-CT arm had invasive mediastinal staging either by M or mediastinal nodal sampling at T. PET-CT was considered positive if N2 or N3 nodes exhibited increased 18 FDG uptake. Results: M was performed in 81 of 143 patients in the PET-CT arm; the remainder had mediastinal nodal staging at T. Combining M with T, the sensitivity and specificity of PET-CT were 0.70 [95% CI: 0.48–0.85] and 0.94 [95%CI: 0.89–0.97], respectively. Of 21 patients with a positive PET-CT, 7 did not have tumor. The positive predictive value (PPV) and negative predictive value (NPV) were 0.67 [95% CI: 0.45–0.83] and 0.95 [95% CI: 0.90–0.98], respectively. The results for PET-CT versus M alone were: sensitivity, 1.0 [95% CI: 0.76–1.0]; specificity, 0.88 [95%CI: 0.79–0.94]; PPV, 0.60 [95%CI: 0.39–0.78]; NPV, 1.0 [95% CI: 0.94–1.0]. Based on PET-CT alone, 7 patients would have been denied T if PET-CT abnormalities had not been evaluated with invasive mediastinal staging. Conclusions: Mediastinal abnormalities on PET-CT should be confirmed by invasive mediastinal staging because of the risk of a false positive test. Patients should not be denied potentially curative therapy based on PET-CT alone. If PET-CT is negative in the mediastinum, the likelihood of occult metastatic disease in the mediastinum is very low and invasive staging may not be required depending on the clinical context. No significant financial relationships to disclose.