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

Abstract

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 (18)F-FDG PET/CT from January 2004 to July 2011. All patients underwent lobectomy and systematic lymph node dissection and preoperative (18)F-FDG PET/CT scanning. The prevalence of occult nodal metastasis in patients as clinical N0 was analyzed according to clinicopathological factors such as tumor location, tumor size, tumor subtype, grade of differentiation and primary tumor SUV(max). 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. SUV(max) 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) ∼T ≤ 3 cm and SUV(max) ≤ 4.3; group 2 (moderate-risk group) ∼T ≤ 3 cm and SUV(max) > 4.3 or SUV(max) ≤ 4.3 and T > 3 cm; group 3 (high-risk group) ∼T > 3 cm and SUV(max) > 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: T(1-2N0M0) NSCLC patients by PET/CT showing larger tumor size and high SUV(max) constitute a high-risk group for occult nodal metastasis. The combined information of primary tumor SUV(max) and tumor size before treatment have potential values in the clinic. These findings would be helpful in selection of SABR or limited surgery candidates.

Keywords: FDG; Non-small cell lung cancer; Occult nodal metastasis; PET/CT; Standard uptake value (SUV); Stereotactic ablative radiotherapy.