Pre-surgical assessment of mediastinal lymph node metastases in patients having ≥ 30 mm non-small-cell lung cancers

Introduction: Computed tomography (CT) and fluorodeoxyglucose-positron-emission-tomography (FDG-PET) measurements of mediastinal lymph nodes (MLNs) of patients with non-small-cell-lung-cancers (NSCLCs) ≤ 30 mm in maximum diameter are recommended for pre-surgical prediction of MLN metastases. Methods: We reviewed all patients at Mount Sinai Health System enrolled in the Initiative for Early Lung Cancer Research on Treatment (IELCART), prospective cohort between 2016 and 2020, who had pre-surgical FDG-PET and underwent surgery with MLN resection and/or pre-operative endobronchial ultrasound (EBUS) for a first primary NSCLC ≤ 30 mm in maximum diameter on pre-surgical CT. Results: Among 470 patients, none with part-solid (n = 63) or nonsolid (n = 23) NSCLCs had MLN metastases. Solid NSCLCs were identified in 384 patients, none in typical carcinoid (n = 48) or NSCLC ≤ 10 mm in maximum diameter (n = 47, including 8 typical carcinoids) had MLN metastases. Among the remaining 297 patients with solid NSCLCs 10.1–30.0 mm, 7 (2.4%) had MLN metastases. Area-under-the-curve (AUC) for predicting MLN metastases in solid NSCLCs 10.1–30.0 mm, using the CT maximum short-axis MLN diameter was 0.62 (95% CI:0.44–0.81, p = 0.18) and using the highest SUVmax of any MLN, AUC was 0.58 (95% CI:0.39–0.78,p = 0.41). Neither AUCs were significantly different from chance alone. Optimal cutoff for prediction of MLN metastases was ≥ 18.9 mm for CT maximum short-axis diameter [sensitivity 14.3% (95%CI:0.0%–57.9%); specificity 100.0% (95%CI:98.9%-100.0%)] and for highest SUVmax was ≥ 11.7 [sensitivity 14.3% (95%CI:0.0%-57.9%) and specificity 99.7% (95%CI:98.3%-100.0%)]. Conclusions: CT and SUVmax had low sensitivity but high specificity for predicting MLN metastases in solid NSCLCs 10.1–30.0 mm. Clinical Stage IA NSCLCs ≤ 30 mm should be based on CT maximum tumor diameter and MLN maximum short-axis diameter ≤ 20 mm.