To determine the incidence of occult N1/N2 nodal metastases and associated risk factors in patients with non-small cell lung cancer no larger than 3cm and deemed cN0 by CT and PET-CT in a prospective, multicentre national database.
Patients with a NSCLC no larger than 3cm, deemed cN0 by PET-CT and CT scan, who had undergone at least a lobectomy, were selected from a national multicentre database of 3533 patients who had undergone anatomic lung resection between 2016 and 2018. Clinical and pathological variables of patients with pN0 and patients with pN1/N2 were compared to identify factors associated with the presence of lymph node metastases. Chi and the Mann-Whitney U test were used for categorical and numerical variables, respectively. All variables with p<0.2 in the univariate analysis were included in the multivariate logistic regression analysis.
The study included 1205 patients from the cohort. The incidence of occult pN1/N2 disease was 10.70% (95%CI, 9.01-12.58). The multivariable analysis revealed that the degree of differentiation, size, location (central or peripheral) and SUV of the tumour in PET, surgeon experience and number of lymph nodes resected were associated with occult N1/N2 metastases.
The incidence of occult N1/N2 in patients with bronchogenic carcinoma with cN0 tumours no larger than 3cm is no negligible. Data about the degree of differentiation, tumour size in CT scan, maximal uptake of the tumour in PET-CT, location (central or peripheral), number of lymph nodes resected and surgeon seniority is relevant in order to detect patients at risk.

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