Original articleGeneral thoracicClinical Significance of Positron Emission Tomography in Subcentimeter Non-Small Cell Lung Cancer

BackgroundThis study evaluated the clinical significance of maximum standardized uptake value (SUVmax) on positron emission tomography (PET) in patients with subcentimeter non-small cell lung cancer (NSCLC).MethodsBetween 2008 and 2014, 189 patients were investigated preoperatively by PET for c-N0 subcentimeter NSCLC, and SUVmax was reviewed. Pathologic invasiveness (PI) was defined as having at least one of the following factors: lymphatic invasion, vascular invasion, pleural invasion, or nodal metastasis. Survival rates were calculated by Kaplan-Meier estimation methods using the log-rank test.ResultsMean SUVmax was 1.7 ± 1.8 (range, 0.6 to 13.0), and the median was 1.0. PI was found in 28 (15%) patients with subcentimeter NSCLC. Multivariate analysis revealed that SUVmax was an independent significant clinical predictor of PI (p = 0.0251) and a prognostic factor of overall survival (OS) (p = 0.0485). A receiver operating characteristics curve elucidated the predictive cutoff value of PI as SUVmax = 2.0. The high-SUVmax group (SUVmax >2.0; n = 42) had significantly more radiologically pure-solid lesions (91% vs 14%; p < 0.0001) and postoperative nodal involvement (12% vs 0%; p < 0.0001) than the low-SUVmax group (SUVmax ≤2.0; n = 147). The 5-year lung cancer-specific OS (LCS-OS) elucidated significant difference between the high-SUVmax and low-SUVmax arms of the study (LCS-OS: 92.3% vs 96.9%, respectively; p = 0.0054), and cancer recurrence was found exclusively in pure-solid subcentimeter NSCLC on thin-section computed tomography. In the high-SUVmax arm of the study, lobectomy was associated with better 3-year recurrence-free survival compared with sublobar resection despite the subcentimeter disease (88.3% vs 50.0%; p = 0.0453).ConclusionsSUVmax on PET reflected tumor invasiveness and had a great impact on the prognosis of subcentimeter NSCLC, especially when a tumor showed a pure-solid appearance on a thin-section computed tomography scan.