Accuracy of positron emission tomography in identifying hilar (N1) lymph node involvement in non-small cell lung cancer: Implications for stereotactic body radiation therapy.

Purpose: To assess the efficacy of preoperative positron emission tomography (PET) to stage the ipsilateral hilum in resected non-small cell lung cancer (NSCLC).

Methods And Materials: All patients who underwent surgery for NSCLC between 1995 and 2008 were evaluated. Patients who underwent preoperative PET imaging at our institution and had hilar nodal sampling were included. Those whose primary tumors extended to the hilum or who received preoperative chemotherapy or radiation therapy were excluded. All PET studies were interpreted by an attending nuclear medicine radiologist and were scored as positive or negative in the hilum or peribronchial area based on visual analysis alone. A 2-sided Fisher exact test compared patient subgroups.

Results: During the time interval, 1558 patients underwent surgery for NSCLC, of whom 484 were eligible for this analysis. The ipsilateral hilum was positive on preoperative PET in 107 patients. The median number of N1 lymph nodes sampled was 4 (range, 1-31). Positive ipsilateral N1 lymph nodes were identified pathologically in 91 patients (19%). Among the 91 patients with involved N1 lymph nodes, 40 were PET positive resulting in a sensitivity of 44%. Among 393 patients without pathologic involvement of hilar lymph nodes, 326 were PET negative resulting in a specificity of 83%. The positive predictive and negative predictive values were 37% and 86%, respectively.

Conclusions: Positron emission tomography appears to have limitations in staging the ipsilateral hilar lymph nodes. Invasive sampling is appropriate if treatment would differ based on the nodal status.