FDG PET/CT and N0 mediastinal nodal status in early stage non-small cell lung cancer: A single institution retrospective experience.

Abstract

11570 Background: The increasing use of CT and now low-dose screening CT scans for at-risk patients have led to increasing detection of lung cancer at early stages. FDG PET/CT is used as an adjunct to conventional imaging to assess loco-regional lymph node spread. However, there is a potential for false-negative results, especially in smaller lesions or early nodal involvement. The main objective of this study was to study the value of PET/CT scan to evaluate for true negative mediastinal nodes in patients with early stage NSCLC. Accurate determination of N0 status can have a significant impact on the cost-effectiveness and timely management of early stage NSCLC. Methods: Of a total of 404 patients with NSCLC managed at our facility between 2008 to 2015, 29 adult patients whose PET scan showed no or equivocal mediastinal nodal involvement and subsequently underwent surgical exploration of mediastinal lymph nodes were included in the study. Data variables that were collected included the cancer site, date of PET, node status on PET, type and date of surgery, cancer histology, and the tissue diagnosis of the sampled nodes. SAS software was used for the analysis of the data. Results: Of the 29 patients with N0 or equivocal nodes on FDG PET/CT, 7 (24.13%) had evidence of malignancy on biopsy of the surgically resected lymph nodes. No statistically significant differences were noted between the site of the neoplastic lesion, cancer histology, duration between the date of PET and the date of surgery in the true negative (TN) and false negative (FN) groups. The recurrence rate was higher in the FN group 60 % (3/5) compared to 21 % (4/19) in the TN group who had follow up for atleast 2 years. Conclusions: Our findings suggest incidence of false negative results of FDG PET/CT for evaluation of N0 nodes in early stage NSCLC is 24.13%. This is comparatively higher than false negatives rates with mediastinoscopy (5-10%) reported in other studies. Although our sample size is small, if confirmed, such a relatively high incidence of false negative results on FDG PET/CT for N0 disease supports the current recommendations for exploratory mediastinoscopy and/or surgery for definitive staging in early stage NSCLC.