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

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.

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.

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%)].

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.