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2013 Reseach Abstract

Incidence of Occult N1 Disease in Patients with Clinical Stage I Non-Small Cell Lung Cancer: Implications for Patients Considered for Stereotactic Body Radiotherapy

Investigators: Adil S. Akthar MD, Mark K. Ferguson MD, Matt Koshy MD, Daniel Appelbaum MD, Wickii T. Vigneswaran MD, Renuka Malik MD

Mentor: Renuka Malik, MD

Purpose/Objectives: Patients receiving stereotactic body radiotherapy (SBRT) for stage I non small cell lung cancer (NSCLC) are typically staged clinically with PET/CT. While PET/CT is associated with a negative predictive value (NPV) of ~90% for occult mediastinal (N2) disease, limited data exist for occult hilar/peribronchial (N1) disease. We hypothesize that PET/CT underestimates spread of cancer to N1 lymph nodes and that future SBRT patients may benefit from increased pathologic staging of these nodal stations.

Materials/Methods: A retrospective study was performed of all patients with clinical stage I NSCLC (AJCC 7th edition) by PET/CT at a single institution from 2003 to 2011, with subsequent surgical resection and lymph node staging. Patients were excluded if PET/CT was performed more than 3 months prior to operation, or if lymph node involvement was “indeterminate” or “equivocal” on imaging. Findings on PET/CT were compared to pathologic nodal involvement to determine NPV. No patients were staged with endoscopic bronchial ultrasound (EBUS) prior to surgery.

Results: 105 patients were eligible for this study. Median age was 68 years [range: 43-87 years]. Only 4 patients (4%) had a previous lung cancer history but were determined to have a second primary cancer on pathologic review. Clinical T-stage distribution was as follows: T1a (43%), T1b (28.5%), and T2a (28.5%). Median time from PET/CT scan to operation was 4 weeks (range: 0.5-12 weeks). Median SUV max was 5.2 [range: 0.7-33.6].

Extent of resection included lobectomy (94%), bilobectomy (4%), and wedge (2%). The median number of N1 nodes sampled was 5 [range; 1-19] and the median number of N2 nodes sampled was 5 [range: 1-25]. Mean pathologic tumor size was 2.62 cm. Histologies included adenocarcinoma (52%), squamous cell carcinoma (33%), large cell carcinoma (10%), and adenosquamous (5%).

A total of 8 of 105 patients (7.6%) were found to have occult N1 metastasis on pathologic review. The NPV of PET/CT for N1 disease among all stage I patients was 92.4%. Five of these 8 patients had T2 tumors. The NPV in patients with clinically-staged T1 and T2 tumors was 72/75 (96%) and 25/30 (83%), respectively (p=0.027). No patients were found to have occult mediastinal nodes.

Conclusion: Our results support pathologic assessment of N1 lymph nodes in stage I NSCLC patients being considered for SBRT, with greatest benefit in patients with T2 tumors. Diagnostic evaluation with endoscopic bronchial ultrasound should be considered in the evaluation of SBRT candidates.

Last Updated: 6/19/14

Updated on June 19, 2014.