Association of maximum standardized uptake value with occult mediastinal lymph node metastases in cN0 non-small cell lung cancer.

OBJECTIVES

The management of non-small cell lung cancer (NSCLC) relies on the tumour-node-metastasis (TNM) stage, and the treatment regimen differs based on the N status. Positron emission tomography-computed tomography (PET-CT) has emerged as a powerful imaging tool for the detection of various cancers with a relatively low false-negative rate. We explored predictors to identify false-negative N2 disease in PET-CT.

METHODS

A total of 284 consecutive cN0 patients with peripheral NSCLC who underwent PET-CT scans followed by curative intent resections were enrolled as a training set to identify predictors of occult N2 metastases by multivariable analysis. The accuracy and cut-off values for the predictors were calculated using a receiver operating characteristic curve. Clinical and pathological data were analysed retrospectively. An additional 151 patients were collected as a test set to validate the results, including the occult N2 rate and accuracy.

RESULTS

In total, 8.5% (24/284) PET-CT-diagnosed N0 NSCLC cases had pathologically diagnosed N2 metastases. The SUV of the primary tumour was a unique independent risk factor for occult N2 NSCLC [P = 0.003, 95% confidence interval = 0.81-0.96, odds ratio (OR) = 0.88]. Occult N2 metastases occurred more frequently in the subcarinal (16/24) and right lower paratracheal lymph nodes (12/24). Accordingly, we divided the patients into two groups by SUV: the occult N2 rates in the SUV of <2.6 and SUV of ≥2.6 groups were 1.0% (1/100) and 12.5% (23/184), respectively (P = 0.001). In the test set, the occult N2 incidence rate was 9.3% (14/151), with the highest rates occurring in the subcarinal (9/14) and right lower paratracheal lymph nodes (6/14). In the two groups defined by SUV, the occult N2 rates were 4% (2/50) and 11.9% (12/101), respectively.

CONCLUSIONS

The SUV of the primary tumour was an independent risk factor for occult N2 metastases in NSCLC patients diagnosed as clinical N0 by PET-CT. SUV of ≥2.6 of the primary tumour may indicate the risk of N2 metastases, and invasive mediastinal staging techniques or comprehensive therapy should not be ignored in these patients.