Risk factors for predicting the occult nodal metastasis in T1-2N0M0 NSCLC patients staged by PET/CT: Potential value in the clinic

Background and objective: The aims of our study were to evaluate the occult nodal metastasis in clinical stage I patients by PET/CT, further investigate the potential risk factors for nodal involvement, since a successful prediction could be helpful in selection appropriate candidates for SABR or limited surgery. Methods: We retrospectively reviewed the records of 189 patients who diagnosed as clinical stage I NSCLC by F-18-FDG PET/CT from January 2004 to July 2011. All patients underwent lobectomy and systematic lymph node dissection and preoperative F-18-FDG PET/CT scanning. The prevalence of occult nodal metastasis in patients as clinical N-0 was analyzed according to clinicopathological factors such as tumor location, tumor size, tumor subtype, grade of differentiation and primary tumor SUVmax. Risk factors for occult nodal metastasis were defined by univariate and multivariate analysis. Results: Occult nodal metastasis was detected in 18.0% (34/189) of the patients. SUVmax of the primary tumor and tumor size were independent predictors of occult nodal metastasis for patients with clinical N-0 NSCLC by FDG PET/CT. Accordingly we divided our patients into three groups: group 1 (low-risk group) similar to T <= 3 cm and SUVmax <= 4.3; group 2 (moderate-risk group) similar to T <= 3 cm and SUVmax >4.3 or SUVmax <= 4.3 and T>3 cm; group 3 (high-risk group) similar to T>3 cm and SUVmax >4.3. The occult lymph node metastasis rate in groups 1, 2, 3 was 1/82 (1.2%), 19/75 (25.3%) and 14/32 (43%) respectively. Conclusions: T1-2N0M0 NSCLC patients by PET/CT showing larger tumor size and high SUVmax constitute a high-risk group for occult nodal metastasis. The combined information of primary tumor SUVmax and tumor size before treatment have potential values in the clinic. These findings would be helpful in selection of SABR or limited surgery candidates. Crown Copyright (C) 2013 Published by Elsevier Ireland Ltd. All rights reserved.